Guidebook for Road Construction and Maintenance Management
December 22, 2016 | Author: Rommel Carlo Largado | Category: N/A
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Guidebook for Road Construction and Maintenance Management...
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IMPROVEMENT OF QUALITY MANAGEMENT FOR HIGHWAY AND BRIDGE CONSTRUCTION AND MAINTENANCE, PHASE II
GUIDEBOOK FOR ROAD CONSTRUCTION AND MAINTENANCE MANAGEMENT
2014
Department of Public Works and Highways
IMPROVEMENT OF QUALITY MANAGEMENT FOR HIGHWAY AND BRIDGE CONSTRUCTION AND MAINTENANCE, PHASE II
GUIDEBOOK FOR ROAD CONSTRUCTION AND MAINTENANCE MANAGEMENT SECOND EDITION
SEPTEMBER 2014
DEPARTMENT OF PUBLIC WORKS AND HIGHWAYS JAPAN INTERNATIONAL COOPERATION AGENCY
Republic of the Philippines DEPARTMENT OF PUBLIC WORKS AND HIGHWAYS OFFICE OF THE SECRETARY Manila
TABLE OF CONTENTS FOREWORD………………………………………………………………………
i
TABLE OF CONTENTS..................................................................................
ii
LIST OF TABLES ...........................................................................................
vi
LIST OF FIGURES .........................................................................................
vii
ACKNOWLEDGMENT ...................................................................................
xii
ACRONYMS .................................................................................................
xiii
Chapter 1
INTRODUCTION.......................................................................
1- 1
1.1
Background ..................................................................................................
1- 1
1.2
Purpose ........................................................................................................
1- 2
Chapter 2
SOIL CLASSIFICATION AND MODULUS ..................................
2- 1
2.1
Unified Soil Classification .............................................................................
2- 1
2.2
Reference Data for Soil Classification ..........................................................
2- 2
2.3
Estimated Soil Modulus by N-value..............................................................
2- 4
Chapter 3
ROAD DRAINAGE ....................................................................
3- 1
Design of Drainage .....................................................................................
3- 1
3.1.1
Estimating Discharge ..............................................................................
3- 1
3.1.2
Capacity of Drainage ..............................................................................
3- 4
3.1.3
Specific Discharge Curve........................................................................
3- 5
Cross Drainage ............................................................................................
3- 7
3.1
3.2
3.2.1
Installation of Cross Drainage .................................................................
3- 7
3.2.2
Headwalls ...............................................................................................
3- 7
Underground Drainage .................................................................................
3- 8
3.3
3.3.1
Function of Underground Drainage.........................................................
3- 8
3.3.2
Typical Cross Section of Underground Drainage System .......................
3- 9
3.3.3
Treatment of Seepage from Mountainous Slope ....................................
3- 9
3.3.4
Underground Drainage on Cut and Embankment Portions ....................
3-10
Chapter 4 4.1
PAVEMENT ...............................................................................
4- 1
Types of Pavement.......................................................................................
4- 1
Guidebook for Road Construction and Maintenance Management
ii
4.1.1
Rigid Pavement.......................................................................................
4- 1
4.1.2
Flexible Pavement ..................................................................................
4- 2
Portland Cement Concrete Pavement ..........................................................
4- 2
4.2
4.2.1
Quality Control ........................................................................................
4- 2
4.2.2
Design Mix and Trial Paving....................................................................
4- 2
4.2.3
Admixture/Additive ..................................................................................
4- 3
4.2.4
Concrete Paving Activities.......................................................................
4- 3
4.2.5
Types of Formworks................................................................................
4- 4
4.2.6
Weakened Plane Joint ............................................................................
4- 4
4.2.7
Replacement of Deteriorated PCC Slabs................................................
4- 6
4.2.8
PCCP Widening ......................................................................................
4- 7
4.2.9
Temperature Control ...............................................................................
4- 7
4.2.10 Surface Texturing ....................................................................................
4- 8
4.2.11 Subbase ..................................................................................................
4- 8
4.2.13 Asphalt Concrete Overlay on PCCP .......................................................
4- 8
4.3
Introduction of Newly Approved Pavement Materials ...................................
4.3.1
Instapave ................................................................................................
4- 9
4.3.2
Pavement Dressing Conditioner .............................................................
4- 9
4.3.3
Polymer Modified Bitumen ......................................................................
4-10
4.3.4
Stone Mastic Asphalt ..............................................................................
4-10
Chapter 5 5.1
SLOPE PROTECTION WORKS ................................................
5- 1
Appropriate Slope .........................................................................................
5- 1
5.1.1
Cut Slope ................................................................................................
5- 1
5.1.2
Embankment Slope.................................................................................
5- 3
Slope Failure ................................................................................................
5- 4
5.2
5.2.1
Soil Slope Collapse .................................................................................
5- 4
5.2.2
Rock Slope Collapse...............................................................................
5- 5
5.2.3
Landslide.................................................................................................
5- 6
5.2.4
Road Slip ................................................................................................
5- 7
5.2.5
Debris Flow .............................................................................................
5- 9
Slope Failure Countermeasures ...................................................................
5-10
5.3
iii
4- 9
5.3.1
Soil Slope Failure Countermeasures ......................................................
5-10
5.3.2
Rock Slope Failure Countermeasures ....................................................
5-11
Guidebook for Road Construction and Maintenance Management
5.4
Slope Erosion Control ..................................................................................
5-11
5.4.1
Slope Drainage .......................................................................................
5-12
5.4.2
Vegetation Works ....................................................................................
5-13
5.4.3
Coconet Bio-engineering ........................................................................
5-16
Slope Protection Structures ..........................................................................
5-21
5.5
5.5.1
Retaining Walls .......................................................................................
5-22
5.5.2
Grouted Riprap .......................................................................................
5-23
5.5.3
Cribwall ...................................................................................................
5-24
5.5.4
Gabion Wall ............................................................................................
5-26
5.5.5
Mechanically Stabilized Embankment Wall (MSE Wall)..........................
5-27
Rock Slope Protection ..................................................................................
5-28
5.6
5.6.1
Cutting and Removal ..............................................................................
5-28
5.6.2
Shotcrete ................................................................................................
5-28
5.6.3
Rocknet...................................................................................................
5-29
5.6.4
Rock Catcher ..........................................................................................
5-30
5.6.5
Rock Shed ..............................................................................................
5-30
5.7
Countermeasures for Landslide ...................................................................
5-30
5.8
Provision of Underground Drainage Pipe thru Boring ..................................
5-30
5.9
Slope Stability Analysis ................................................................................
5-32
Chapter 6 6.1
RIVER AND COASTAL EROSIONS ..........................................
6-1
River Erosion ................................................................................................
6- 1
6.1.1
Examples of Road Damages caused by River Erosion ..........................
6- 2
6.1.2
Countermeasures for River Erosion........................................................
6- 2
Coastal Erosion ............................................................................................
6-13
6.2
6.2.1
Case 1: Scouring of Foundation .............................................................
6-13
6.2.2
Case 2: Washout of Backfill Materials.....................................................
6-15
6.2.3
Case 3: Collapse of Mainbody ................................................................
6-17
6.2.4
Countermeasures for Coastal Erosion ....................................................
6-18
Chapter 7 7.1
ROAD SAFETY .........................................................................
7- 1
Road Signs...................................................................................................
7- 1
7.1.1
Classifications .........................................................................................
7- 1
7.1.2
Standard Application ...............................................................................
7- 3
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7.1.3
Design .....................................................................................................
7- 4
7.2
Weighbridge Station .....................................................................................
7- 4
7.3
Road Warning System..................................................................................
7- 6
Chapter 8 8.1
8- 1
Weather Monitoring ......................................................................................
8- 1
8.1.1
Rain Gauges ...........................................................................................
8- 1
8.1.2
Weather Station ......................................................................................
8- 2
Visual Inspection of Pavement .....................................................................
8- 2
8.2
8.2.1
ROCOND ................................................................................................
8- 2
8.2.2
Portable Falling Weight Deflectometer (FWD) ........................................
8- 2
Slope Investigation .......................................................................................
8- 8
8.3
8.3.1
Measurement ..........................................................................................
8- 8
8.3.2
Visual Slope Investigation .......................................................................
8- 9
8.3.3
Digital Clinometer ....................................................................................
8-11
Slope Monitoring ..........................................................................................
8-16
8.4
8.4.1
Crack Monitoring .....................................................................................
8-16
8.4.2
Wire Extension Meter ..............................................................................
8-16
Soil Investigations.........................................................................................
8-17
8.5
8.5.1
Boring and Core Sampling ......................................................................
8-17
8.5.2
Sounding for Soil Strength Test...............................................................
8-18
Ground Water Survey and Monitoring ..........................................................
8-21
8.6
8.6.1
Ground Water Logging ............................................................................
8-21
8.6.2
Hand Held Water Quality Sensor ............................................................
8-23
Strain Gauge with PVC Pipe ........................................................................
8-24
8.7
v
MONITORING AND INVESTIGATION ........................................
8.7.1
Summary of Pipe Strain Gauge ..............................................................
8-24
8.7.2
Checklist for Installation of Pipe Strain Gauge ........................................
8-24
8.7.3
Strain Gauges Monitoring .......................................................................
8-24
8.7.4
Digital Strain Meter..................................................................................
8-27
Guidebook for Road Construction and Maintenance Management
LIST OF TABLES Table 2.1
Unified Soil Classification System (Sands and Gravels) ...................
2- 1
Table 2.2
Unified Soil Classifications (Silts, Clays and Organic Soils) ..............
2- 2
Table 2.3
Soil Classification Reference Data for Preliminary Design ................
2- 3
Table 2.4
N-value and Internal Friction Angle (Sand) ........................................
2- 4
Table 2.5
N-value and Unconfined Compressive Strength (Clay) .....................
2- 4
Table 3.1
Drainage Area....................................................................................
3- 1
Table 3.2
Values of Runoff Coefficient, C ..........................................................
3- 2
Table 3.3
Design Flow Return Period................................................................
3- 3
Table 3.4
Manning’s Roughness Coefficient .....................................................
3- 4
Table 3.5
Appropriate Range of Flow Velocity ..................................................
3- 5
Table 3.6
Installation of Cross Drainage ...........................................................
3- 7
Table 4.1
Requirements for Admixtures ............................................................
4- 3
Table 4.2
Types and Functions of PCCP Joints ................................................
4- 5
Table 4.3
Size and Length of Dowel/Tie Bars ...................................................
4- 6
Table 4.4
Preventive Measures for Reflection Cracks on AC Overlay ..............
4- 9
Table 4.5
Material Composition of Pavement Dressing Conditioner .................
4-10
Table 5.1
Cutting Height and Cut Slope ............................................................
5- 1
Table 5.2
Standard Cut Slope Gradient for Japan Highways ............................
5- 2
Table 5.3
Japan’s Standard Gradients for Road Embankment Slopes .............
5- 4
Table 5.4
Applicable Cut Slope .........................................................................
5-14
Table 5.5
Physical properties (Coconet) ...........................................................
5-16
Table 5.6
Physical properties (Cocolog) ............................................................
5-17
Table 5.7
Materials Requirement for Grouted Riprap and Stone Masonry........
5-24
Table 5.8
Required Safety Factor for Landslide Countermeasures...................
5-33
Table 6.1
Countermeasures against River Erosions .........................................
6- 3
Table 6.2
Required Depth and Width of Groundsill ...........................................
6-10
Table 6.3
Countermeasures for Coastal Erosion ..............................................
6-18
Table 7.1
Maximum Allowable Vehicle Weight ..................................................
7- 5
Table 8.1
Poisson's Ratio ..................................................................................
8- 4
Table 8.2
Specific Displacement Level for FWD ...............................................
8- 5
Table 8.3
Drop Height of Weight for Main Test ..................................................
8- 5
Table 8.4
Estimation of N-value from Nd-value of SDCP ..................................
8-20
Table 8.5
Criteria for Groundwater Logging ......................................................
8-22
Table 8.6
Objected Water Properties ................................................................
8-23
Table 8.7
Criteria for Evaluation of Data of Strain Gauges................................
8-25
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vi
LIST OF FIGURES Figure 3.1
Rainfall Intensity Duration Frequency (RIDF) Curves Source: 328 Baguio Synoptic Station..............................................................
Figure 3.2
3- 3
Rainfall Intensity Duration Frequency (RIDF) Curves Source: 646 Mactan Synoptic Station .............................................................
3- 3
Figure 3.3
Hydraulic Radius Formula .................................................................
3- 5
Figure 3.4
Specific Discharge Curve (Luzon) .....................................................
3- 6
Figure 3.5
Specific Discharge Curve (Visayas) ..................................................
3- 6
Figure 3.6
Specific Discharge Curve (Mindanao) ...............................................
3- 6
Figure 3.7
Typical Inlet and Outlet Headwalls .....................................................
3- 7
Figure 3.8
Structure of Headwall ........................................................................
3- 8
Figure 3.9
Relation of Water Content and CBR ..................................................
3- 8
Figure 3.10 Typical Underground Drainage for a 2-lane Road .............................
3- 9
Figure 3.11 Typical Underground Drainage for a 4-lane Road .............................
3- 9
Figure 3.12 Typical Underground Road Drainage for Mountainous Terrain ..........
3- 9
Figure 3.13 Treatment of Seepage from Mountainous Slope ...............................
3- 10
Figure 3.14 Underground Drainages on Cut and Embankment Sections .............
3- 10
Figure 4.1
Conceptual Figure Showing Load Distribution for Rigid and Flexible Pavements ......................................................
4- 1
Figure 4.2
Flowchart for Preparatory Work for Concrete Paving ........................
4- 2
Figure 4.3
Concrete Paving Activities .................................................................
4- 3
Figure 4.4
Paving Works ....................................................................................
4- 4
Figure 4.5
PCCP Joints and Load Transfer Device ............................................
4- 5
Figure 4.6
Deteriorated PCCP ............................................................................
4- 6
Figure 4.7
PCCP Widening.................................................................................
4- 7
Figure 4.8
PCCP Widening Work .......................................................................
4- 7
Figure 4.9
Thermometer .....................................................................................
4- 7
Figure 4.10 Texturing of the Surface .....................................................................
4- 8
Figure 4.11 Laying of Base Materials by Means of Road Grader and Paver ........
4- 8
Figure 5.1
Geology and Slope Gradient .............................................................
5- 3
Figure 5.2
Typical Soil Slope Collapse ...............................................................
5- 5
Figure 5.3
Typical Rock Slope Collapse .............................................................
5- 5
Figure 5.4
Typical Landslide ...............................................................................
5- 6
Figure 5.5
Road Slip ...........................................................................................
5- 7
Figure 5.6
Typical Road Slip ...............................................................................
5- 7
Figure 5.7
Stages of Road Slip ...........................................................................
5- 7
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Guidebook for Road Construction and Maintenance Management
Figure 5.8
Landslide Caused by Water Infiltration from Road ............................
5- 8
Figure 5.9
Road Slip due to Slope Erosion .........................................................
5- 8
Figure 5.10 Surface Flow Concentrations ............................................................
5- 9
Figure 5.11 Road Slip caused by Leakage from Pipe Culvert ..............................
5- 9
Figure 5.12 Typical Debris Flow ...........................................................................
5-10
Figure 5.13 Selections of Soil Slope Failure Countermeasures ...........................
5-10
Figure 5.14 Selections of Rock Slope Failure Countermeasures .........................
5-11
Figure 5.15 Relation between Slope and Rainfall.................................................
5-11
Figure 5.16 Erosion on Cut Slope.........................................................................
5-12
Figure 5.17 Relations between Content Ratio of Fines and Natural Water Content ................................................................
5-12
Figure 5.18 Surface Water Overtopping Slope Drainage .....................................
5-13
Figure 5.19 Inappropriate Vegetation Work ..........................................................
5-14
Figure 5.20 Wicker Works as Vegetation Base ....................................................
5-14
Figure 5.21 Vetiver Grass .....................................................................................
5-15
Figure 5.22 Sketch of slope to be protected with Vetiver Grass ...........................
5-15
Figure 5.23 Coconet (CGN 700) ...........................................................................
5-17
Figure 5.24 Cocolog/Fascine (CGR 200) .............................................................
5-17
Figure 5.25 Stakes ...............................................................................................
5-17
Figure 5.26 Coco Coir Peat ..................................................................................
5-18
Figure 5.27 Ropes ................................................................................................
5-18
Figure 5.28 Typical Cross Sections for Bio-Engineering Works ...........................
5-19
Figure 5.29 Site Preparation .................................................................................
5-20
Figure 5.30 Laying of Nets....................................................................................
5-20
Figure 5.31 Anchoring ..........................................................................................
5-21
Figure 5.32 Sewing...............................................................................................
5-21
Figure 5.33 Hydroseeding ....................................................................................
5-21
Figure 5.34 Gravity Type (Rock Catcher Retaining Wall) .....................................
5-22
Figure 5.35 Leaning Type Retaining Wall .............................................................
5-22
Figure 5.36 Construction steps for Stone Masonry ..............................................
5-23
Figure 5.37 Construction steps for Grouted Riprap ..............................................
5-23
Figure 5.38 Grouted Riprap ..................................................................................
5-24
Figure 5.39 Stone Masonry Cribwall.....................................................................
5-25
Figure 5.40 Reinforced Concrete Crib and Pitching Wall .....................................
5-25
Figure 5.41 Reinforced Concrete Frame with Vegetation Works ..........................
5-26
Figure 5.42 Gabion Wall .......................................................................................
5-26
Figure 5.43 Constructed Gabion Wall at a Location with Seepage ......................
5-27
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viii
Figure 5.44 Mechanically Stabilized Embankment by means of Geotextile fabrics
5-27
Figure 5.45 Mechanically Stabilized Embankment Wall (Terree Armee Wall).......
5-27
Figure 5.46 Relation between Rock Slope Height and Height of Bounce of Stone
5-28
Figure 5.47 Cutting and Removal of Unstable Rock Slope...................................
5-28
Figure 5.48 Shotcrete ...........................................................................................
5-29
Figure 5.49 Rocknet .............................................................................................
5-29
Figure 5.50 Rock Catcher .....................................................................................
5-30
Figure 5.51 Rock Shed .........................................................................................
5-30
Figure 5.52 Rainfall and Groundwater Level ........................................................
5-31
Figure 5.53 Typical Underground Drainage Pipe Installations ..............................
5-31
Figure 5.52 Fellenius Method ...............................................................................
5-32
Figure 6.1
Degradation due to Riverbed Erosion................................................
6- 1
Figure 6.2
Riverbank Erosion at Bend ................................................................
6- 2
Figure 6.3
Riverbank Erosion caused by Overflow .............................................
6- 2
Figure 6.4
Riverbed Erosion ...............................................................................
6- 2
Figure 6.5
Selection of River Erosion Countermeasures Flowchart ...................
6- 3
Figure 6.6
Types of Revetment Works................................................................
6- 4
Figure 6.7
Design Procedure for River Revetment Work ....................................
6- 5
Figure 6.8
Typical Cross Section of Revetment Works.......................................
6- 5
Figure 6.9
Laying of Concrete Blocks on River Slope ........................................
6- 6
Figure 6.10 Sample Arrangement of Groundsills ..................................................
6- 7
Figure 6.11 Typical section of Groundsill ..............................................................
6- 7
Figure 6.12 Design Procedure for Groundsill........................................................
6- 8
Figure 6.13 Arrangement of Groundsills Relative to the Direction of Flow ...........
6- 9
Figure 6.14 Details of Groundsill...........................................................................
6- 9
Figure 6.15 Typical Section of Groundsill .............................................................
6-10
Figure 6.16 Rechanneling Concept for Riverbank and Riverbed Protections .......
6-11
Figure 6.17 Type of Spur Dike ..............................................................................
6-11
Figure 6.18 Typical Cross Sections of Spur Dike..................................................
6-12
Figure 6.19 Examples of Road Damages caused by Coastal Erosion .................
6-13
Figure 6.20 Collapse of Coastal Revetment due to Scouring of Foundation Bed .
6-14
Figure 6.21 Conceptual Diagram of Scouring of Foundation Bed ........................
6-14
Figure 6.22 Collapse of Coastal Revetment .........................................................
6-15
Figure 6.23 Collapse of Coastal Revetment due to Washout of Backfill Materials
6-16
Figure 6.24 Washout of Backfill Material...............................................................
6-16
Figure 6.25 Collapse of Coastal Revetment due to Washed out Backfill Material
6-16
Figure 6.26 Collapse of Coastal Revetment due to Overtopping ..........................
6-17
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Figure 6.27 Levels of Erosion of Grouted Riprap Surface ....................................
6-17
Figure 6.28 Collapsed Revetment due to Progression of Cracks .........................
6-18
Figure 6.29 Conceptual Design of Coastal Slope Revetment ..............................
6-19
Figure 6.30 Selection of Countermeasures against Coastal Erosion ...................
6-20
Figure 6.31 Typical Foundation Water Cut-off Wall ..............................................
6-21
Figure 6.32 Considerations for Coastal Revetment Design ..................................
6-22
Figure 7.1
Regulatory Signs (Type R) ................................................................
7- 2
Figure 7.2
Warning Signs (Type W)....................................................................
7- 2
Figure 7.3
Guide or Informative Signs (Type G) .................................................
7- 2
Figure 7.4
Instructional Signs (Type S) ...............................................................
7- 3
Figure 7.5
Hazard Markers (Type HM) ...............................................................
7- 3
Figure 7.6
Weighbridge Stations ........................................................................
7- 4
Figure 7.7
Road Status and Information System ................................................
7- 6
Figure 8.1
Manual Data Collection from a Standard Rain Gauge.......................
8- 1
Figure 8.2
Standard Rain Gauge ........................................................................
8- 1
Figure 8.3
Weighing Precipitation Rain Gauge ...................................................
8- 1
Figure 8.4
Weather Station .................................................................................
8- 2
Figure 8.5
Setting up of FWD .............................................................................
8- 3
Figure 8.6
The Drop Rig .....................................................................................
8- 3
Figure 8.7
The Mainbody and Display Instrument ..............................................
8- 3
Figure 8.8
Measure Display of Portable FWD ....................................................
8- 4
Figure 8.9
Estimated Engineering Property ........................................................
8- 6
Figure 8.10 Example of Analysis Sheet for Portable FWD ...................................
8- 7
Figure 8.11 Rough Determination of Slope Height and Angle ..............................
8- 8
Figure 8.12 Road Slope Survey by Digital Distance Meter ...................................
8- 8
Figure 8.13 Digital Distance Meter .......................................................................
8- 8
Figure 8.14 Visual Slope Investigation (1/2) .........................................................
8- 9
Figure 8.15 Visual Slope Investigation (2/2) .........................................................
8- 9
Figure 8.16 Block Diagram of Complex Earth Slide/Earth Flow ...........................
8-10
Figure 8.17 Typical Configuration and Phenomena of Earth Slide .......................
8-10
Figure 8.18 Important Locations for Slope Investigation on Cut Slope .................
8-10
Figure 8.19 Strike and Dig ....................................................................................
8-11
Figure 8.20 Clinometer .........................................................................................
8-11
Figure 8.21 Parts of Digital Clinometer .................................................................
8-12
Figure 8.22 Usage of Digital Clinometer ...............................................................
8-12
Figure 8.23 Crack Displacement Measurement ...................................................
8-16
Figure 8.24 Wire Extension Meter ........................................................................
8-16
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x
Figure 8.25 Sample Core Boring at Landslide Portion..........................................
8-17
Figure 8.26 Sample Core Boring at Soft Rock Slide .............................................
8-17
Figure 8.28 Schematic Diagram of Standard Penetration Test .............................
8-18
Figure 8.29 Dynamic Cone Penetrometer (Dual Mass Type) ...............................
8-18
Figure 8.30 Operation of DCP ..............................................................................
8-19
Figure 8.31 Simplified Dynamic Cone Penetrometer ............................................
8-19
Figure 8.32 Friction Loss on Simplified Dynamic Cone Penetrometer Test ..........
8-20
Figure 8.33 Simplified Dynamic Cone Penetrometer (Sample Output) ................
8-21
Figure 8.34 Schematic Diagram of Groundwater Logging ....................................
8-22
Figure 8.35 Sample Graph of Groundwater Logging ............................................
8-22
Figure 8.36 Pipe Strain Gauge .............................................................................
8-24
Figure 8.37 Sample Pipe Strain Gauge Monitoring ..............................................
8-25
Figure 8.38 Monitoring of Pipe Strain Gauge (Sample Output) ............................
8-26
Figure 8.40 Monitoring of Pipe Strain Gauge (Sample Profile) .............................
8-27
Figure 8.42 Connection with Half Bridge Type ......................................................
8-29
Figure 8.41 Strain Gauges with PVC Pipe ............................................................
8-29
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Guidebook for Road Construction and Maintenance Management
ACKNOWLEDGEMENT In behalf of the CWG on Road Manuals Improvement, the Group Leader acknowledges the TWG members and the regional project managers of pilot regions for their patience, guidance, words of encouragement and useful critiques which really helped us a lot in accomplishing this undertaking. TWG Members: Dr. Judy F. SESE, Chairperson, OIC-Director, Bureau of Research and Standards Ms. Carolina S. CANUEL, Fmr. Vice Chairperson, Fmr. Div. Chief, DPD, P/S Mr. Adriano M. DOROY, Asst. Director, Bureau of Design Mr. Aristarco M. DOROY, OIC-Asst. Director, Bureau of Construction Ms. Edna F. MEÑEZ, OIC-DE, Negros Occidental 4th DEO, DPWH-Region VII Mr. Felipe S. RAMOS, Fmr. Chief, Technical Services and Evaluation Div., BRS Mr. Nestor B. CAOILE, OIC-Division Chief, Materials Testing Division, BRS Regional Project Managers: Ms. Elsa T. NABOYE, Regional Project Manager, Asst. Chief, QAD, DPWH-CAR Ms. Ramie B. DOROY, Regional Project Manager, DE, Negros Oriental 1st DEO, DPWH-Region VII Ms. Rowena P. JAMITO, Regional Project Manager, Engr. V, MD, RO-XI Thank you also to CWG Members for their efforts and collaborations. CWG Members: Mr. Jay Jenner R. BIARES, Engr. III, CAR ; Group Leader Mr. Elmer R. FIGUEROA, Engr. III, BOC Mr. Ernante S. ANTONIO, Engr. III, BOM Ms. Carina B. DIAZ, Engr. III, BOD Ms. Nenita R. VALENCIA, Former Engr. III, BRS Mr. Vicente R. VALLE, JR., Engr. IV, DPWH-Region VII Ms. Aurora M. LACASANDILE, Engr. III, CD, DPWH-Region XI Finally, we wish to thank our Expert, Mr. Ryoichi Yamasaki, Co-Team Leader, JICA TCP II and his Asst. Engineer, Mr. Feliciano P. Carpio, for their support and encouragement throughout this activity.
Guidebook for Road Construction and Maintenance Management
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ACRONYMS A AASHTO
American Association of State Highway and Transportation Official
AC
Asphalt Concrete
ACP
Asphalt Concrete Pavement
ASTM
American Society for Testing and Materials
B BOC
Bureau of Construction
BOD
Bureau of Design
BOE
Bureau of Equipment
BOM
Bureau of Maintenance
BRS
Bureau of Research and Standards
BST
Bituminous Surface Treatment
C CAR
Cordillera Administrative Region
CBR
California Bearing Ratio
CSB
Cold Seal Bitumen
CWG
Counterpart Working Group
D DCP
Dynamic Cone Penetrometer
DE
District Engineer
DENR
Department of Environment and Natural Resources
DEO
District Engineering Office
DO
Department Order
DPWH
Department of Public Works and Highways
F FCSEC
Flood Control and Sabo Engineering Center
FWD
Falling Weight Deflectometer
xiii
Guidebook for Road Construction and Maintenance Management
G GIS
Geographical Information System
GOJ
Government of Japan
GOP
Government of the Philippines
GPS
Global Positioning System
GVW
Gross Vehicle Weight
H HDM-4
Highway Development and Management Version 4
HE
Highway Engineer
I IRI
International Roughness Index
J JICA
Japan International Cooperation Agency
JCC
Joint Coordinating Committee
L LAAV
Los Angeles Abrasion Value
M ME
Materials Engineer
MO
Memorandum Order
MSE
Mechanically Stabilized Embankment
N NEDA
National Economic and Development Authority
P PAGASA
Philippine Atmospheric, Geophysical and Astronomical Services Administration
PCC
Portland Cement Concrete
PCCP
Portland Cement Concrete Pavement
PDC
Pavement Dressing Conditioner
PMB
Polymer Modified Bitumen
PMS
Pavement Management System
Guidebook for Road Construction and Maintenance Management
xiv
PS
Planning Service
Q QA
Quality Assurance
QC
Quality Control
R RCBC
Reinforced Concrete Box Culvert
RCP
Reinforced Concrete Pipe
RCPC
Reinforced Concrete Pipe Culvert
RIDF
Rainfall Intensity Duration Frequency
RMMS
Routine Maintenance Management System
RO
Regional Office
ROCOND
Visual Road Condition Rating System
ROW
Right-of-Way
RS
Road Safety
S SDCP
Simplified Dynamic Cone Penetrometer
SMA
Stone Mastic Asphalt
SPT
Standard Penetration Test
T TARAS
Traffic Accident Recording and Analysis System
TCP
Technical Cooperation Project
TOR
Terms of Reference
TWG
Technical Working Group
V VCI
xv
Visual Condition Index
Guidebook for Road Construction and Maintenance Management
Chapter 1
Introduction
1.1 Background The Department of Public Works and Highways, hereinafter referred to as DPWH and Japan International Cooperation Agency, hereinafter referred to as JICA, agreed in 2006 to implement the project for Improvement of Quality Management for Highway and Bridge Construction and Maintenance, hereinafter called as " Phase I", aiming to enhance the engineering knowledge of the engineers of DPWH. For implementation of the said project, the DPWH organized the Joint Coordinating Committee, hereinafter called as JCC, Technical Working Group, hereinafter called as TWG and Counterpart Working group, hereinafter called as CWG and the JICA dispatched the JICA Technical Cooperation Project Team, hereinafter referred to as "JICA TCP Team" from February 2007 to February 2010. Under Phase I, the following manuals/guidelines were prepared and issued for road construction and maintenance through the CWG's activities. *
Guidebook for Road Construction and Maintenance Management in the Republic of the Philippines,
*
Road Project Management and Supervision Manual, Volume I: Main Text and
*
Road Project Management and Supervision Manual, Volume II: Appendices (Standard Forms, Examples and References)
From October 2011 to September 2014, the DPWH and JICA TCP Team -newly dispatched by JICA - implemented the project for Improvement of Quality Management for Highway and Bridge Construction and Maintenance, Phase II, hereinafter called as Phase II to aim further enhancement. This manual, Guidebook for Road Construction and Maintenance was prepared under Phase II through the revision work done by CWG based on the Guidebook mentioned above. The Guidebook was made through consolidations of seminars and On-the-Job-Training materials, texts, presentations and is mainly focused on the engineering knowledge necessary for road and slope management.
Guidebook for Road Construction and Maintenance Management
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1.2 Purpose Engineers of the DPWH concerned with road and slope construction and maintenance are the main targets of this Manual. The CWG made efforts to make this Reference easy to understand by the young Engineers, especially beginners, hence, it would be an effective tool related to the above areas.
1-2
Guidebook for Road Construction and Maintenance Management
Chapter 2
Soil Classification and Modulus
2.1 Unified Soil Classification Table 2.1 and 2.2 show the Soil Classification utilized for field identification.
Clean sand (little or fines)
Gravel with fines (applicable amount of fine)
Clean gravel (little or fines)
Unified Soil Classification System (Sands and Gravels)
Sand with fines (applicable amount of fine)
Gravels More than half of coarse Fraction is smaller than no.4 sieve size Sands More than half of coarse fraction is smaller than no.4 sieve size (for visual classification, the 1/4" size may be used as equivalent to the no.4 sieve size)
Coarse grained soils More than half of material is bigger than no. 200 sieve size
Table 2.1
Wide range in grain size and substantial amount of all intermediate particle size Predominantly one size or a range of sizes with some intermediate sizes missing Non-plastic fines (for identification procedures, See ML) Plastic fines (for identification, See CL) Wide range in grain size and substantial amount of all intermediate particle size Predominantly one size or range of range of sizes with some intermediate sizes missing
Group Symbols
Typical Names
GW
Well graded gravels, gravel-sand mixtures little or no fines
GP
GM
GC
SW
Well graded sands, gravelly sands, little or no fines
SP
Poorly graded sands, gravelly sands, little or no fines
Non-plastic fines (for identification, See ML)
SM
Non-plastic fines (for identification, See CL)
SC
Guidebook for Road Construction and Maintenance Management
Poorly graded gravels, gravel-sand mixtures little or no fines Silty gravels, poorly graded grave-sand silt mixtures Clayey gravels, poorly graded-sand clay mixtures
Silty sand, poorly graded sand-silt mixtures Clayey sands, poorly graded sand-clay mixtures
2-1
Table 2.2
Unified Soil Classifications (Silts, Clays and Organic Soils)
Silts and clays Liquid limit less than 50 Silts and clays Liquid limit greater than 50
Fine graided soils More than half of material is smaller than no. 200 sieve size
Dry strength (Crushing characteristics)
Highly organic soil
Dilitancy (Reaction to shaking)
Toughness (Consisten cy near plastic limit)
Group Symbols
None to slight
Quick to slow
None
ML
Medium to high
None to very slow
Medium
CL
Slight to Midium
Slow
Slight
OL
Slight to medium
Slow to none
Slight to Medium
MH
High to very high
None to very slow
High
CH
Medium to high
None to very slow
Slight to Medium
OH
Readily identified by color, odor, spongy feel and frequently fibrous texture
P+
Typical Names
Inorganic silts and very fine sands, rock flour, silty or clayey fine sands with slight plasticity Inorganic clays of low to medium plasticity gravelly clays, sandy clays, silty-clays, lean clays Organic silts and organic silt-clays of low plasticity Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts Inorganic clay of high plasticity < fat clays Organic clays of medium to high plasticity Peat and other highly organic soils
2.2 Reference Data for Soil Classification In DPWH, there is no available reference data for soil classification for use in preliminary design. Table 2.3 shows a reference data for preliminary design of Japan Expressway for DPWH Engineer's references.
2-2
Guidebook for Road Construction and Maintenance Management
Table 2.3
Embankment Material
Soil Type Gravely soil or Sand with some gravel Sand Sand Sand and Gravel Fine grained sand
Well grained Compacted Poor grained Compacted Compacted Compacted
20
40
0
GW, GP
20
35
0
SW
19
30
0
SP
19
25
30 or less
SM, SC
18
15
50 or less
ML, CL MH, CH
Gravel
Dense, or well grained
20
40
0
GW
Gravel
Not dense, or poor grained
18
35
0
GP
Dense
21
40
0
SW
Not dense
19
35
0
SP
Sand
Dense or well grained
20
35
0
--
Sand
Loose or poor grained
18
30
0
--
Silty Sand
Dense
19
30
30 or less
SM, SC
Silty Sand
Loose
17
25
0
SM, SC
Cray
Stiff, N-value is 8-15
18
25
50
ML,CL
Cray
Moderate, N-value is 4-8
17
20
30
ML,CL
Cray
Soft, N-value is 2-4
16
15
15
ML,CL
Silt
Stiff, N-value is 8-15
17
25
50
CH,MH,ML
Silt
Moderate, N-value is 4-8
16
15
30
CH,MH,ML
Silt
Soft, N-value is 2-4.
14
10
15
CH,MH,ML
Sand and Gravel Sand and Gravel
Undisturved Material
Soil Classification Reference Data for Preliminary Design Internal Unit weight Unified Soil Cohesion Condition friction angle (kN/m3) Classification (kN/m3) (degree) Compacted
(Source: Design Guideline for Japan Expressway)
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2.3 Estimated Soil Modulus by N-value Table 2.4 shows the relation between internal friction angles and N-values (Reference : Terzaghi and Peck). Table 2.4
N-value and Internal Friction Angle (Sand) Internal Friction Angle
N-value
Density
0 to 4
Very loose
less than 28.5
4 to10
Loose
28.5 to 30
10 to30
Medium
30 to 36
30 to50
Dense
36 to 41
More than 50
Very dense
More than 41
(Degree)
Table 2.5 shows the relation between unconfined compressive strength and N-value (Reference: Terzaghi and Peck). Table 2.5
N-value and Unconfined Compressive Strength (Clay)
0 to2
Very soft
Unconfined Compressive Strength kN/m2 less than 25
2 to4
Soft
25 to 50
12.5 to 25
4 to8
Medium
50 to 100
25 to 50
8 to15
Stiff
100 to 200
50 to 100
15 to30
Very Stiff
200 to 400
100 to 200
30 or more
Hard
400 or more
200 or more
N-value
2-4
Consistency
Cohesion (for short-time load) kN/m3 less than 12.5
Guidebook for Road Construction and Maintenance Management
Chapter 3 3.1
Road Drainage
Design of Drainage
3.1.1 Estimating Discharge The peak discharge can be estimated by the Rational formula as shown below:
Qd = where:
1 ×C × I × A 3.6 Qd =
peak discharge (m3/s)
C=
runoff coefficient
I=
rainfall intensity (mm/hour) for a critical time period
A= 3.1.1.1
drainage area (catchment area) (km2)
Drainage Area
The drainage area (catchment area) shall be identified or estimated through field survey and utilization of topographic map. Each type of road drainage has its designated drainage area as shown in Table 3.1. Table 3.1 Type of Drainage
Drainage Area Drainage Area (Catchment Area)
Road Surface Drain
Road surface (carriageway and shoulder)
Road Slope Drain
Roadside (including road slopes and mountain slopes)
Road Side Drain
Road surface and adjoining road slope, adjoining residential area etc.
Cross Drain
Road surface, adjoining road slope, adjoining residential area and other basin area (if necessary)
3.1.1.2
Runoff Coefficient
The runoff coefficient, C, represents runoff rate of rainfall. The value is provided as shown in Table 3.2.
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3-1
Table 3.2
Values of Runoff Coefficient, C
Type of Surface
Factor C
Cement Concrete or Asphalt Concrete Pavement
0.9 to 1.0
Bituminous Surface Treatment
0.7 to 0.9
Gravel Surface
0.3 to 0.6
Residential Area/City
0.3 to 0.6
Residential Area/Town & Village
0.2 to 0.5
Rocky Surface
0.7 to 0.9
Bare Clay Surface
0.7 to 0.9
Forested Land (sandy and clay)
0.3 to 0.5
Flattish Cultivated Areas (not flooded)
0.3 to 0.5
Steep or Rolling Grassed Areas
0.5 to 0.7
Flooded or Wet Paddies
0.7 to 0.8
(Source: DPWH, Design Guidelines, Criteria and Standards) 3.1.1.3
Rainfall Intensity
The rainfall intensity, "I", is derived from the maximum estimated rainfall for the design flow return period and time of concentration. Time of concentration, "Tc", is the time required for runoff from the farthest point of the drainage area (catchment area) to reach the design target point. Generally, concentration time can be estimated by the following formula:
Tc = where:
L1.15 51H 0.385 Tc =
time of concentration in minutes
L=
length of watershed along the mainstream in meters
H=
difference in elevation between the most distant ridge in the watershed along the mainstream and the target point in meters
The design flow return period for the rainfall intensity is provided in Table 3.3.
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Guidebook for Road Construction and Maintenance Management
Table 3.3
Design Flow Return Period
Structure Type
Design Flow Return Period
Bridges
50 years
Box Culverts
25 years
Pipe Culverts
15 years
Side Drainage
5 years
Surface Drainage
2 years
(Source: DPWH, Design Guidelines, Criteria and Standards) Rainfall intensity charts were prepared based on the data obtained from PAGASA as shown in Figure 3.1 and 3.2. 500
200
100y
400
50y
350
25y
180
Return Period 100 years 50 years
160
25 years 10 years
300 10y
Rainfall R (mm/hr)
Rainfall R (mm/hr)
450
5 years
250
2 years
140
120
100
5y 200
80
150
60
2y
100
40
50
20
0
0 0
10
20
40
30
50
60
0
380
Figure 3.1
720
1050
1440
Duration t (min)
Duration t (min)
Rainfall Intensity Duration Frequency (RIDF) Curves Source: 328 Baguio Synoptic Station
250
120
Return Period 100 years
100y 50y
25 years 10 years
25y
Rainfall R (mm/hr)
Rainfall R (mm/hr)
100
50 years
200
5 years 150
10y
2 years
5y
80
60
100 2y
40
50
20
0
0 0
10
20
30
40
50
60
0
360
Duration t (min)
Figure 3.2
720
1030
1440
Duration t (min)
Rainfall Intensity Duration Frequency (RIDF) Curves Source: 646 Mactan Synoptic Station
Guidebook for Road Construction Maintenance Management
3-3
3.1.2 Capacity of Drainage Discharge of drainage can be estimated by the following formula:
Qc = a × v 1 × R 2 / 3 × i1 / 2 n 1 Qc = a × × R 2 / 3 × i1 / 2 n v=
where:
3.1.2.1
a=
effective cross-sectional area, m2
v=
flow velocity,m/s
n=
Manning’s roughness coefficient
i=
hydraulic radius, m
R=
gradient of water surface
Manning’s Roughness Coefficient
Table 3.4 shows Manning’s Roughness Coefficient, n. Table 3.4
Manning’s Roughness Coefficient Condition
Type of Channel
Good
Fair
Bad
Brick in cement mortar,brick sewers
.012
.013
.015
.017
Smooth cement surface
.010
.011
.012
.013
Concrete pipe
.012
.013
.015
.016
Concrete lined channel
.012
.014
.016
-
Cement rubble surface
.017
.020
.025
.030
Dredged earth canals
.025
.027
.030
.033
Canals with rough stone bed, weeded slope
.025
.030
.035
.040
Earth bottom, rubble side
.028
.030
.033
.035
Clean straight bank
.025
.027
.030
.033
Winding
.033
.035
.040
.045
Sluggish river weedy reaches
.050
.060
.070
.080
Very weedy reaches
.075
.100
.125
.150
Natural Stream
Best
(Source: DPWH Design Guidelines, Criteria and Standards) 3.1.2.2
Hydraulic Radius
Below are the different formulas in determining the hydraulic radius:
3-4
Guidebook for Road Construction and Maintenance Management
r
1:m(=H:L)
H
Φ
m・H
H
B
H = r (1 − cos φ ) R = 0.5r (1 −
a = r 2 (φ −
R=
sin 2φ ) 2φ
B⋅H B + 2⋅ H
１：ｍ1
m1 + m2
１：ｍ
H sin(φ1 + φ2 ) 2 sin φ1 + sin φ2
R=
H 2
a=
H2 H2 ( m1 + m2 )or = × (cot φ1 + cot φ2 ) 2 2
1 + m12 + 1 + m22
or
H
Φ
H
Φ1
Φ2
H (B + m ⋅ H ) B + 2 ⋅ H 1 + m2
H ( B + H ⋅ c oφ )t o r B + 2 ⋅ H ⋅ c o e sφ c
1 sin( 2φ )) 2
１：ｍ
Figure 3.3 3.1.2.3
R=
H Φ
B
R=
H 2 1+
a =
H2 m 2
m 1 + m2
mH
or
or =
H cos φ 2 1 + sin φ
H2 × cot φ 2
Hydraulic Radius Formula
Flow Velocity
Table 3.5 shows appropriate range of flow velocity by type of drainage structure and type of drainage surface. In case the computed actual flow velocity is higher or lower than the ranges, the structure should be redesigned. Table 3.5
Appropriate Range of Flow Velocity
Structure Drainage Surface
Type of
Type of
Types
Range of Flow Velocity (m/sec)
Road Side Drain
0.5 to 1.0
Pipe Culvert (910mm.)
0.6 to 1.0
Pipe Culvert (greater than 910mm.)
0.8 to 2.0
Cement Concrete
0.6 to 3.0
Asphalt Concrete
0.6 to 1.5
Stone/Brick
0.6 to 1.8
Gravel
0.6 to 1.0
Coarse Sand
0.3 to 0.6
Silt
0.1 to 0.2
3.1.3 Specific Discharge Curve In case the watershed is vast, the specific discharge curve can be applied to estimate the
Guidebook for Road Construction Maintenance Management
3-5
peak discharge as shown in Figures 3.4 to 3.6 used by DPWH FCSEC and JICA in March, 2003 under the Project for the Enhancement of Capabilities on Flood Control and Sabo Engineering. 100
Specific Discharge q; m3/s/(km2)
Luzon Return Period 100 years 50 years 25 years 10 years 5 years
10
2 years
1
0.1 1
10
100
10,000
1000
100,000
Catchment Area A (km2)
Figure 3.4
Specific Discharge Curve (Luzon)
100
Specific Discharge q; m3/s/(km2)
Visayas Return Period 100 years 50 years 25 years 10 years 5 years
10
2 years
1
0.1 1
10
100
1000
10,000
100,000
Catchment Area A (km2)
Figure 3.5
Specific Discharge Curve (Visayas)
100
Specific Discharge q; m3/s/(km2)
Mindanao
10
Return Period 100 years 50 years 25 years 10 years 5 years 2 years 1
0.1 1
10
100
1000
10,000
100,000
Catchment Area A (km2)
Figure 3.6
3-6
Specific Discharge Curve (Mindanao)
Guidebook for Road Construction and Maintenance Management
3.2 Cross Drainage 3.2.1 Installation of Cross Drainage Basically there are three alternatives for vertical alignment of cross drainage as shown in Table 3.6. Table 3.6
Installation of Cross Drainage
Alternative-1
Alternative-2
Alternative-3
Figure
Advantages
Disadvantages
The construction and maintenance costs will be cheaper owing to its simple design. The slope of the embankment at the outlet portion will be prone to scouring hence, proper drainage outlet structures should be provided.
Water will be easily drained.
The flow might be controlled to mitigate slope and pipe damages.
There is no need to provide drainage outlet along the embankment slope however, protective measures at the outlet portion should be provided to minimize the scouring effect of the rapid flow.
Construction and maintenance costs are high due to longer pipes.
3.2.2 Headwalls Basically, inlet/outlet headwalls for cross drainage should be provided to prevent scouring and erosion as shown in Figure 3.7.
Figure 3.7
Typical Inlet and Outlet Headwalls
Guidebook for Road Construction Maintenance Management
3-7
Joints between Culvert Box, Wing Wall and Apron shall be checked to be connected water tight.
Dumped Stone with grouted surface Skirt (toe)
Figure 3.8
Apron and Skirt (Toe) shall be connected to prevent water from seeping into the bottom of culvert.
Structure of Headwall
3.3 Underground Drainage 3.3.1 Function of underground drainage High water contents in road base material enormously affect the strength(bearing capacity) of the pavement . Figure 3.9 shows the relationship between CBR of road base material and its water contents. To keep the road base material in good condition, provision of underground drainage system is recommended. 6
CBR (%)
4
2
0 60
Figure 3.9
3-8
80
100 120 Water Content (%)
140
160
Relation of Water Content and CBR
Guidebook for Road Construction and Maintenance Management
3.3.2 Typical Cross Section of Underground Drainage System Figures 3.10 to 3.12 show typical cross sections of road with underground drainage. Underground drainage should be recommended as required per existing condition.
Underdrains on both sides of the road
Figure 3.10
Typical Underground Drainage for a 2-lane Road
Underdrains on both sides and at the median
Figure 3.11
Typical Underground Drainage for a 4-lane Road
Underdrain on one side
Figure 3.12
Typical Underground Road Drainage for Mountainous Terrain
3.3.3 Treatment of Seepage from Mountainous Slope In case of road embankment on the natural slopes, seepage and/or surface water from mountainous slopes should be treated as shown in Figure 3.13.
Guidebook for Road Construction Maintenance Management
3-9
Construction of Road Embankment on the slope with seepage from side slope Seepage from side slope
Bench Cut
Base Rock Layer
Recommended treatment of underground water Cutoff Trench with Blind Pipe Drain Layer wrapped with Geotextile Drain Pipe
Figure 3.13
Treatment of Seepage from Mountainous Slope
3.3.4 Underground Drainage on Cut and Embankment Portions Underground drainages shall be installed at cut and embankment portions as shown in Figure 3.14.
Embankment Under-drain Cut Slope
Under-drain
Figure 3.14
3 - 10
Underground Drainages on Cut and Embankment Sections
Guidebook for Road Construction and Maintenance Management
Chapter 4
Pavement
4.1 Types of Pavement Road pavement is of two major types - rigid pavement (PCCP) and flexible pavement (ACP).
Figure 4.1
Conceptual Figure Showing Load Distribution for Rigid and Flexible Pavements
4.1.1 Rigid Pavement A rigid pavement generally consists of three layers: the concrete slab, subbase and subgrad as described below: Slab
The slab is made of reinforced or plain concrete which also includes load transfer devices and joint sealing materials. The concrete slab acts like a bridge girder over the subgrade.
Subbase
It is the portion of the pavement structure between the subgrade and the slab. It usually consists of compacted layer/s of granular materials.
Subgrade
It is the bottom portion of the pavement structure which consists of suitable embankment materials or existing road bed.
Guidebook for Road Construction and Maintenance Management
4-1
4.1.2 Flexible Pavement A flexible pavement generally consists of four layers: surface course, base course, subbase and subgrade (which is the prepared roadbed) as described below: Surface Course
It consists of a mixture of mineral aggregates and bituminous materials constructed on a prepared base course.
Base Course
It is the portion of a pavement structure immediately beneath the surface course. It consists of aggregates such as crushed stone, crushed slug, crushed or uncrushed gravel and sand or a combination of these materials placed and compacted on a prepared subbase.
Subbase
It is the portion of the pavement structure between the subgrade and the base course. It consists of a compacted layer of granular materials placed on a prepared subgrade.
Subgrade
It is the bottom portion of the pavement structure which consists of suitable embankment materials or existing road bed.
4.2 Portland Cement Concrete Pavement 4.2.1 Quality Control The Contractor shall perform all sampling, testing and inspection necessary to assure quality control of the component materials of the concrete. The Contractor shall be responsible for determining the gradation of fine and coarse aggregates and for testing the concrete mixture for slump, air content and temperature. He shall conduct his operations so as to produce a mix conforming to the approved mix design.
4.2.2 Design Mix and Trial Paving The Contractor is obliged to formulate the design mix, conduct trial mix and trial paving for approval of the Project Engineer before commencement of pavement construction as illustrated in Figure 4.2. Material Test
Figure 4.2
4-2
Design Mix and Trial Mix
Trial Paving
Approval of Design Mix and Methodology
Start Paving
Flowchart for Preparatory Work for Concrete Paving
Guidbeook for Road Construction and Maintenance Management
4.2.3 Admixture/Additive Admixture/additive shall be added only to the concrete mix to produce some desired modifications to the properties of concrete whenever necessary, but not as partial replacement of cement. The admixtures shall conform to the requirements as tabulated below: Table 4.1 Type Air-entraining admixture Chemical admixture Fly Ash
Requirements for Admixtures Requirement AASHTO M154 AASHTO M194 ASTM C618
Remarks
As 20% partial replacement of portland cement in concrete mix
4.2.4 Concrete Paving Activities The following photos show concrete pouring activities:
Preparation and cleaning
Moistening prior to placing
Transport of concrete (for slipform paver)
Placing of Concrete
Conduct of slump test
Checking of temperature of the mix
Checking of the thickness
Finishing by means of a floater
Finishing by means of a screeder
Checking of the texturing Tool
Texturing of the surface
Spraying of curing compound
Provision of protective cover sheets
Sawing of weakened plane joint
Checking the depth and width of the joint
Figure 4.3
Concrete Paving Activities
Guidebook for Road Construction and Maintenance Management
4-3
4.2.5 Types of Formworks There are two types of formworks for concrete paving - fixed-form and slip form. The use of slipform paver is required in DPWH road projects as per D.O. 219 Series of 2000.
Using Fixed Form
Using Slipform Paver
Figure 4.4
Paving Works
4.2.6 Weakened Plane Joint All joints shall be protected from the intrusion of injurious foreign material until sealed. All joints shall be cut within 4 to 24 hours after pouring and thereafter sealed with asphalt sealant. The depth of the weakened plane joint shall not be less than 50 mm while the width not more than 6 mm. Only concrete saw is permitted in the cutting of weakened plane joints. According to international practice, dowel bars are required in all contraction joints (at 4.5m) as load transfer device for PCCP with thickness of more than 200 mm. The PCCP slabs without dowel bars at weakened joint will cause various defects in the medium to long term, especially for the road route on which heavy trucks are dominant. However, this has not yet become a standard practice of the DPWH due to cost constraints. Presently, the application is by specific road section and upon approval of the concerned DPWH Office in consultation with BOD. The types and functions of PCCP joints are summarized below.
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Guidbeook for Road Construction and Maintenance Management
Table 4.2
Category and Type
Transverse Joints**
Longitudinal Joints
Contraction Joint/ Weakened Plane Joint
Expansion Joints Construction Joints
Formed Joints Formed Joints Sawed Contrac tion Joint Formed Joints Formed Joints
Types and Functions of PCCP Joints
Function
Load Transfer Method (Device) Tie bar(Deformed)
Shrinkage Crack Prevention Construction by lane Shrinkage Crack Prevention At every 4.5m Shrinkage Crack Prevention At every 4.5m
With dowel bar* Round Bar * Without dowel
Expansion Force Release Joint for interruption of work and end of day’s construction
Dowel Bar(Round) Tie Bar(Deformed)
* Bar size varies depending on pavement thickness **No transverse joint shall be constructed within 1.50 m of concrete block.
Tie Bars for Longitudinal Joints (Deformed Bar) Dowel Bars (Round Bar)
Figure 4.5
PCCP Joints and Load Transfer Device
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4-5
Tie bars are installed across longitudinal joints to hold the two slabs in close contact or to prevent them for separating. Tie bars are located at mid-depth of the pavement. Dowel bars are placed in contraction joints and in some construction joints when it falls at full block (4.5m) to transfer a portion of the load across the joint and to hold the two slab ends at the same elevation. To function properly, dowels must be parallel to the surface and to the centerline of the pavement. Length and size of bars vary depending on pavement thickness as shown in Table 4.3. Table 4.3
Type Tie Bar(Deformed) Dowel Bar(Round)*
Size and Length of Dowel/Tie Bars
PCCP Thickness (mm) 200 230 200 230 250 280
Size* (mm)
Length (mm) 12 16 25 28 32 36
Spacing (mm)
1,000 600 600 600 600 600
600 750 300 300 300 300
* 1/8 of PCCP thickness
4.2.7 Replacement of Deteriorated PCCP Slabs The replacement of shattered PCC slabs is one of the common works involved in both rehabilitation and maintenance projects. Procedures are as follows: (1) The Engineer and the Contractor conduct joint inspections prior to the commencement of work to confirm the current conditions and identify the PCC slabs to be replaced. (2) The Contractor removes broken/deteriorated PCCP slabs in accordance with the Plans, Specifications or as directed by the Engineer. (3) The subgrade and subbase course are prepared in accordance with the specifications or as directed by the Engineer. (4) Existing tie bars on longitudinal joints are to be retained if these are still in good condition. Where necessary, new tie bars shall be installed on drilled holes and bonded with high viscosity epoxy resin. (5) Install forms; side surfaces of the existing PCCP shall be cleaned. (6) Pour concrete; perform the required surface texturing, cutting and curing. (7) Thoroughly clean the joints and apply sealants adequately. Figure 4.6
4-6
Deteriorated PCCP
Guidbeook for Road Construction and Maintenance Management
4.2.8 PCCP Widening The widening of existing PCCP is one of the common works involved in upgrading work. Procedures are likely the same as the replacement of deteriorated PCCP slabs.
Figure 4.7
PCCP Widening
Drilling of holes for Tie Bars
Placing Concrete
Note) Workers must wear safety gears.
Figure 4.8 *
PCCP Widening Work
The provision for widening blocks at curves shall be poured simultaneously with the adjoining lane.
*
Weakened plane joints at curves shall be perpendicular to the centerline.
4.2.9 Temperature Control The Engineer shall require that measures be taken into consideration to prevent the temperature of concrete mix from exceeding 32oC because shrinkage cracks occur when the concrete is placed at a high temperature, which may include any or all of the following: a)
Addition of ice blocks in the water.
b)
Shading and water sprinkling of aggregates, formworks and steel bars.
c)
Shading of working area.
d)
In transporting concrete using trucks, provide necessary cover sheets.
e)
Placing of concrete at a time when the humidity is low.
Figure 4.9
Thermometer
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4.2.10 Surface Texturing Surface texturing is necessary to keep a skid resistant surface and is done after the surface has hardened enough.
Figure 4.10
Texturing of the Surface
4.2.11 Subbase The subbase materials shall be spread on the prepared subgrade and compacted to the required thickness.
Figure 4.11
Laying of Base Materials by Means of Road Grader and Paver
4.2.13 Asphalt Concrete Overlay on PCCP Asphalt concrete overlay is a standard repair work both for routine and preventive maintenance. It is laid on the existing pavement after the repair of distress. In overlaying, preventive measures against reflection cracks shall be considered. Methods to prevent reflection cracks are as shown in Table 4.4.
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Guidbeook for Road Construction and Maintenance Management
Table 4.4
Preventive Measures for Reflection Cracks on AC Overlay
Types
Methods
Aggregate Intermediate
Required Laying of aggregate base materials
Layer Asphalt Concrete Crack Relief Layer
Remarks minimum thickness is 15cm.
Laid over the existing PCCP to prevent cracks from extending to the newly laid asphalt concrete.
Required minimum thickness is 9 cm.
This item shall consist of either a single application of bituminous material followed by a single spreading of Surface Treatment
aggregate (single bituminous surface treatment), or two applications of bituminous material each followed by a spreading of aggregate (double bituminous surface treatment) in accordance with the Plans and Specifications.
Crack and Seat Technology
Cracking of the existing PCC pavement with dimension of 0.5 x 0.5m. using guillotine or arrow hammer and rolling it with pneumatic roller.
4.3 Introduction of Newly Approved Pavement Materials 4.3.1 Instapave Instapave is a technology used for improving road surface condition. It consists of a blend of Cold Seal Bitumen (CSB), aggregate, water and additives applied on a prime coated base or on a tack coated concrete/asphalt pavement in accordance with the Plans and Specifications.
4.3.2 Pavement Dressing Conditioner Pavement Dressing Conditioner (PDC) is a surface treatment material for asphalt concrete pavement consisting of a blend of coal tar and petroleum oil. It is designed to penetrate the pavement surface to replace critical elements necessary to rejuvenate and rehabilitate the asphaltic binder thereby increasing pavement plasticity and flexibility while reducing viscosity. Since it has already become an integral part of the pavement, it does not wear off under traffic and prevents raveling.
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Pavement Dressing Conditioner (PDC) is composed of materials as shown below. Table 4.5
Material Composition of Pavement Dressing Conditioner
Materials 1. Refined Coal-tar (Gravel RH2) 2. Light aromatic solvent 3. Naphtha or coal-tar solvent naphtha 4. Blend of tar oils 5. Elastomer
Remarks 30% to 40% 30% to 40% 30% to 40% 15% to 40% 0.01% to 13%
4.3.3 Polymer Modified Bitumen Polymer Modified Bitumen (PMB) is a material for porous asphalt pavement. The mixture is open graded asphalt wearing course applied on asphalt concrete or portland cement concrete pavement. The porous asphalt mixture is composed of large proportion of coarse aggregate, small proportion of fine aggregate, mineral filler and PMB. This mixture has air voids within the range of 18% to 25% that easily allows the passage of water.
4.3.4 Stone Mastic Asphalt Stone Mastic Asphalt (SMA) is a gap graded hot mix asphalt surface course composed of high proportion of coarse aggregate, fine aggregate, mineral filler, bituminous material and cellulose fiber. Cellulose fibers either pure or bitumen coated, shall be added to the mix to absorb the excess binder and to improve the properties of the asphalt mix. Generally, SMA is not applicable on bridge decks.
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Guidbeook for Road Construction and Maintenance Management
Chapter 5
Slope Protection Works
5.1 Appropriate Slope 5.1.1 Cut Slope Natural ground is extremely complex and not uniform in its properties and cut slopes tend to gradually become unstable after the completion of work. Therefore, stability calculation is necessary only in rare cases when examining the stability of cut slopes. An overall judgment shall be made by fully taking into account the requirements for its stability described later by referring to the standard values of the gradient of slope listed in Table 5.1. Table 5.1 Soil/Rock Properties
Soil
Cutting Height and Cut Slope Cutting Height
Slope (Ratio)
H
(H:V)
Hard Rock
7.0 m
0.25:1 to0.5:1
Soft Rock
7.0 m (max)
0.5:1 to 1:1
2.0 m or less
2:1
Over 2.0 m
1.5:1
2.0 m or less
2:1 to 4:1
Over 2.0 m
1.5:1 to2:1
a. cohesive b. less cohesive
Note: 1.
Indicated gradient (ratio) is subject to change depending on the stability of soil materials.
2.
When the cutting height exceeds 7.0 m for rock materials and 5.0 m. for soil, benching is applied.
3.
In case of heavy weathering or erosion, this table is applicable only after adequate protection work is applied.
(Source: DPWH FCSEC Technical Standards and Guidelines for Planning and Design Vol. IV)
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5-1
For reference, shown below is Japan’s standard gradient for cut slope. Table 5.2
Standard Cut Slope Gradient for Japan Highways Cut slope height (m)
Materials of Ground
Slope (Ratio) (H:V)
Hard rock
0.3:1 to 0.8:1
Soft rock Loose and poor grain
Sand
Unconditional
0.5:1 to 1.2:1 1.5:1
size distribution. 5 m or less
0.8:1 to 1.0:1
5 to 10 m
1.0:1 to 1.2:1
5 m or less
1.0:1 to 1.2:1
5 to 10 m
1.2:1 to 1.5:1
Dense or well grain
10 m or less
0.8:1 to 1.0:1
Sandy soil with
size distribution
10 to 15 m
1.0:1 to 1.2:1
gravel or rock
Loose, bad grain size
10 m or less
1.0:1 to 1.2:1
distribution.
10 to 15 m
1.2:1 to 1.5:1
Silt, clay
10 m or less
0.8:1 to 1.2:1
5 m or less
1.0:1 to 1.2:1
5 to 10 m
1.2:1 to 1.5:1
Dense Sandy soil Loose
Fine-grained soil
Fine-grained soil with some cobbles, boulders Notes: When a single cut slope cannot be adopted due to different soil composition or other reasons, the cut slope height and gradient are determined on the basis of the following
ha: Cut slope height for slope surface a
considerations:
hb: Cut slope height for slope surface b
*
The gradient does not include a berm.
*
The cut slope height to the relevant slope gradient means the total cut slope height including all cut slopes above the relevant cut slope.
It is important that an overall judgment of critical slope gradient be based on observation of similar type slopes. As shown in Figure 5.1, the gradient of slopes varies depending on the geology. Berm is generally installed at boundary of slope gradient difference.
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Guidebook for Road Construction and Maintenance Management
Figure 5.1
Geology and Slope Gradient
On cut slopes, berms 1.0 to 2.0 m. wide are generally provided for every 5.0 to 7.0 m. in height for the following purposes: *
To enhance slope stability.
*
To reduce the speed of surface water flow thereby decreasing the scouring force on cut slope.
*
To provide space for ditches.
*
To be used as pathwalk during inspection or as support area of scaffolding for repair works.
A wider berm is recommended where rockfall protection fences are to be installed. When drainage is not provided, about 5 to 10% of transversal gradient is normally provided for the berm to drain water towards the toe of the slope. If the slope is prone to erosion, the berm should be sloped inwards.
5.1.2 Embankment Slope For the standard gradient for embankment slope, please refer to DPWH Highway Design Guidelines, Criteria and Standards.
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For reference, shown below is Japan’s standard gradient for road embankment slopes. Table 5.3
Japan’s Standard Gradients for Road Embankment Slopes Embankment slope height
Slope (Ratio)
(m)
(H:V)
Sand of well grain size
5 m or less
1.5:1 to 1.8:1
distribution
5 to 15 m
1.8:1 to 1.20:1
10 m or less
1.8:1 to 2.0:1
10 m or less
0.8:1 to 1.0:1
10 to 20 m
1.8:1 to 2.0:1
Sandy soil, stiff fine-grained
5 m or less
0.8:1 to 1.0:1
soil
5 to 10 m
1.0:1 to 1.2:1
Volcanic clay
5 m or less
1.8:1 to 2.0:1
Materials of Embankment
Sand of poor grain size distribution Rock lump, rock muck
Note: Embankment height is defined as from slope toe to slope shoulder. Slope shoulder Embankment Height
Slope toe
It is required that there is enough bearing capacity of embankment base and no expected inundation. (Source: ‘Highway Earthwork Guideline, Japan Road Association, March 1999’)
5.2 Slope Failure 5.2.1 Soil Slope Collapse
5-4
*
Part of the mountain side slope suddenly collapses on the road.
*
Mostly triggered by rainfall infiltration.
*
Collapsed/collapsible materials are soil and highly weathered rocks.
*
Prone to occur on steep slopes.
*
The volume involved is generally from 200 to 5000 cubic meters.
Guidebook for Road Construction and Maintenance Management
Figure 5.2
Typical Soil Slope Collapse
5.2.2 Rock Slope Collapse *
Free falling or rolling down of rocks along the slope.
*
Falls occur due to gravity and are controlled by the distribution of joints. Materials are hard, jointed rocks.
*
Prone to occur on steep slope and cliff.
Figure 5.3
Typical Rock Slope Collapse
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5-5
5.2.3 Landslide Landslide refers to all types of slope failures and defined as movement of a large mass of soil and/or rocks. Charateristics of a landslide are as follows: *
A portion of the road bulges up by an inch or more.
*
It is triggered by water infiltration and/or earthquake.
*
Materials are soil and highly weathered rocks.
*
It usually occurs on a gentle and irregular mountain slopes.
*
The volume involved is generally more than 5000 cubic meters.
Figure 5.4
5-6
Typical Landslide
Guidebook for Road Construction and Maintenance Management
5.2.4 Road Slip *
Road
slip
occurs
because
of
the
collapse/scouring/caving-in of the valley side slope of the roadway. *
Occurs mostly on road shoulder.
*
Occurs mostly along stream bends.
*
Mostly induced by infiltration/leakage of water from road surface/damaged drainage facilities.
*
Materials are soil and highly weathered rocks.
Figure 5.5
Figure 5.6
Road Slip
Typical Road Slip
5.2.4.1 Road Slip Process Infiltration of rainfall through the cracks accelerates the process of slipping. Monitoring of these cracks and preventive measures to reduce road slip risks are necessary such as filling of cracks with impervious materials. A typical process of the development of open cracks on a shoulder slope is shown in Figure 5.7.
→ Expansion
→ Sliding/displacement
Figure 5.7
Compression
Stages of Road Slip
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5-7
5.2.4.2 Road Slip due to Water Infiltration Water infiltration is a major cause of road slope failure. It is important that inflow from above cut slope should be controlled and discharged to proper outfall sites.
Road
Road Drain
Swelling Road
Slide
Road (Source: Japan Highway Public Cooperation 1982, Slope Inspection Guide 1) Figure 5.8
Landslide Caused by Water Infiltration from Road
5.2.4.3 Road Slip due to Slope Erosion and Inadequate Drainage Road slip starts with slope erosion. Slope erosion results from infiltration of water into the road bed due to inadequate drainage sytems which eventually lead to gradual sliding of the slope. At this stage, countermeasures will become expensive hence, properly designed drainage system should be undertaken.
Figure 5.9
5-8
Road Slip due to Slope Erosion
Guidebook for Road Construction and Maintenance Management
Also, concentration of surface water triggers road slip therefore, proper drainage facilities shall be instituted to address such condition.
Figure 5.10
Surface Flow Concentrations
5.2.4.4 Road Slip due to Leakage from Damaged Pipe Culvert Leakage from damaged culvert will also cause road slip. It is therefore important to identify the cause and extent of the problem and to conduct immediate repair works.
Figure 5.11
Road Slip caused by Leakage from Pipe Culvert
5.2.5 Debris Flow Debris flow refers to the rapid flow of boulders, gravel, sand, silt clay and trees mixed with a large quantity of water that is mainly generated when a slope collapses during heavy rainfall. Conditions of debris flow- prone stream are as follows; *
Gradient of stream bed is more than 15 degrees (debris flow stops if less than 10 degrees).
*
Catchment area is more than 5 has.
*
Existence of debris beside the road (debris flow reoccurs frequently).
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5-9
Figure 5.12
Typical Debris Flow
5.3 Slope Failure Countermeasures 5.3.1 Soil Slope Failure Countermeasures The following countermeasures are applicable for soil slope: *
Slope Drainage Works
*
Cribwall
*
Vegetation Works
*
Mechanically
*
Retaining Wall
Stabilized
Embankment
Wall(MSE Wall) *
Gabion Wall
START
Is there high risk of soil slope failure or landslide?
YES
NO Is there seepage from slope? Or do you assume high water table?
YES
NO
Does the area have many records of slope failure?
YES
NO Removal of unstable mass, Retaining wall, Masonry works,, Catch wall for collapsed soil, Slope drainage and/or Combination of above.
Figure 5.13
5 - 10
Removal of unstable mass, Retaining wall, Masonry works Catch wall for collapsed soil, Vegetation works, Slope Drainage Combination of above.
Removal of unstable mass, Retaining wall, Gabion wall, Vegetation works, Slope drainage, Underdrains, Horizontal boring and/or Combination of above.
Removal of unstable mass, Retaining wall, Gabion wall, Crib wall, Anchor works, Pile works, Vegetation works, Slope daraiange, Underdrains, Horizontal boring and/or Combination of above.
Selections of Soil Slope Failure Countermeasures
Guidebook for Road Construction and Maintenance Management
5.3.2 Rock Slope Failure Countermeasures The following countermeasures are applicable for rock slope: *
*
Removal and Cutting of
*
Retaining Wall
Unstable and Isolated
*
Shotcrete
Rocks
*
Rocknet
Slope Drainage Work
*
Cribwall
START
Is there high risk of rock slope failure or rock fall?
YES
NO Is there seepage from slope? Or is the slope weathered?
YES
NO
Does the area have many records of slope failure? Are there isolated stones/rocks
YES
NO Removal of unstable mass, Retaining wall, Masonry works,, Catch wall for rolling stones, and/or Combination of above.
Figure 5.14
Removal of unstable mass, Retaining wall, Masonry works Catch wall for rolling stones, Vegetation works (if able), Slope Drainage Combination of above.
Removal of unstable mass, Retaining wall, Masory works, Vegetation works (if able), Horizontal boring, Shotcrete and/or Combination of above.
Removal of unstable mass, Retaining wall, Crib wall, Anchor works, Horizontal boring, Shotcrete, Rocknet, Rockshed and/or Combination of above.
Selections of Rock Slope Failure Countermeasures
5.4 Slope Erosion Control Gentle slope is more stable however, the degree of exposure to erosion is higher. In such
Rainfall per slope area
condition, erosion countermeasures such as slope drainage, vegetation, etc. are required.
Slope (o)
Figure 5.15
Relations between Slope and Rainfall
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5 - 11
There are many slope failures due to erosion after construction because cut slopes are left bare and are not provided with necessary slope protection works. The countermeasure to be provided shall be vegetation works as much as possible.
Figure 5.16
Erosion on Cut Slope
5.4.1 Slope Drainage Figure 5.17 shows the primary causes of slope instability. Soil of 40 - 60% fines proportion and contains high natural water contents (more than 40%) is prone to slope failure because it is moderately pervious and easily saturated. In such case, it is necessary to provide
Natural Water Content of Colluvial Deposit (%)
a slope drainage. Sample Stable slope Unstable slope
80
Unstable
60
40
Stable
20
Stable 0
0
20
40
60
80
100
Content Ratio of Fines (passing 74 micron sieve) in Matrix of Colluvial Deposit (%)
(Source: Okusono 1979, Japan Highway Public Cooperation Laboratory Report) Figure 5.17
Relations between Content Ratio of Fines and Natural Water Content
5 - 12
Guidebook for Road Construction and Maintenance Management
The vertical and horizontal alignment of slope drainage shall be smooth curve without sharp bends as shown in Figure 5.18.
Slope Drainage (Vertical and Horizontal)
Sharp Bend
Overtopping
Overtopping Slope Erosion Figure 5.18
Surface Water Overtopping Slope Drainage
5.4.2 Vegetation Works 5.4.2.1 Purpose The purposes of vegetation are as follows: (a) Reduce surface erosion caused by running water and rainfall impact. (b) Reduce infiltration of rain water. (c) Bind subsurface soil with root systems, and (d) Improve the landscape of the cut slope. 5.4.2.2 Applicable Conditions Slope vegetation can mitigate slope erosion only therefore, it is recommended on stable soil slopes. The type of vegetation shall be selected considering important factors such as rainfall, temperature, slope gradient, and soil properties.
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Table 5.4 Geology Soft rock, fine grained soil Coarse grained soils
Applicable Cut Slope
Gradient Horizontal: Vertical 1.0 to 1.2:1 or less (45 or 40 degrees or less) 1.5:1 or less (35 degrees or less)
Applicability
Generally, only vegetation work is applied on this kind of soil slope.
In this case, vegetation work alone is not enough to prevent soil erosion Intermediate condition between upper and lower therefore, combinations with other categories countermeasures such as wicker works are recommended. Soft rock, fine grained More than 0.8:1 Vegetation work is not applicable. soil, coarse grained soils (More than 50 degrees) (Source: Highway Earthwork Guideline, Published by Japan Road Association, March 1999) 5.4.2.3 Wicker Works In case the slope of fine grained soil is 45 degrees or more, a combination of vegetation
and
wicker
works
is
recommended. In Figure 5.10, Coconet was installed with vegetation work but collapsed due to slope erosion. Figure 5.19
Figure 5.20
5 - 14
Inappropriate Vegetation Work
Wicker Works as Vegetation Base
Guidebook for Road Construction and Maintenance Management
5.4.2.4 Planting of Vetiver Grass Vetiver grass is a kind of gramineous plant whose roots could penetrate up to 3 m. deep and grows approximately 1m high.
Figure 5.21
Vetiver Grass
To determine the applicability of vetiver grass, trial planting is recommended considering the following: 1) The top soil should be 0.5 to 2.0 m. deep. 2) Geological investigation should be conducted to verify the depth of solid strata 3) It should be planted at intervals of 1.0 m. 4) After a heavy rain, conduct field investigation to check possible occurrence and depth of collapse. 5) The applicability of vetiver grass can now be evaluated.
(Reference: IDI November,2008) Figure 5.22
Sketch of slope to be protected with Vetiver Grass
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5 - 15
5.4.3 Coconet Bio-engineering For controlling soil erosion, installation of coconut coir fiber made into geonets such as coconets/mats, cocologs/fascines, cocotwines and coco peat as bioengineering materials is advisable. The following terms are used in this technology. Coconut Geonets
any coconut coir fiber-based placed on sloping ground and embankments to hold the vulnerable soil and permit vegetative growth to control surface erosion and preserve the productivity of the soil.
Coconet
coconut coir fiber twine woven into blankets of different density.
Cocolog/Fascine
a tubular structure of coconut coir fiber blankets of different diameter filled with coco coirand/or coco peat.
Coco Coir Twine
a string made of coconut coir strands twisted together.
Coco Coir Peat
a natural and residual materials from coconut coir which serves as soil conditioner.
5.4.3.1 Material (1)
Coconut Coir Coconut coir fiber materials for use in fabrication of coconut geonets shall be a multi-cellular fiber with 12 to 24 microns in diameter and the ratio of length to diameter shall be 35. The fiber shall also be hygroscopic, with moisture content of 10% to 12% at 65% humidity and 22% to 55% at 95% relative humidity.
(2)
Coconet and Cocolog/Fascine The hand-spun coco coir twine that is to be woven into coconut geonets shall have a diameter of 5mm plus or minus 10%. The coco coir twine shall have a tensile strength of not less than 150N. Coconet and cocolog/fascine shall conform to Tables 5.5 and 5.6, respectively. Table 5.5
Average Number of
Average Number of
Twines at Crosswise
Twines at
Direction
Lenghtwise Direction
Coconet 400
40
40
400
Coconet 700
40
70
700
Coconet 900
70
70
900
Type of Coconet
5 - 16
Physical properties (Coconet) Density (min) (gm/𝑚2 )
Guidebook for Road Construction and Maintenance Management
Table 5.6
Physical properties (Cocolog) Diameter (min)
Weight (min)
(cm)
(Kg/m)
Cocolog 100
10
2.0
Cocolog 200
20
4.5
Cocolog 300
30
10
Cocolog 400
40
20
Cocolog 500
50
30
Type of Cocolog/Fascine
Figure 5.23
Figure 5.24 (3)
Coconet (CGN 700)
Cocolog/Fascine (CGR 200)
Bamboo Stakes Bamboo stakes shall be mature and shall be 3 to 4 cm. wide and 25 to 30 cm. long.
(4)
Live Plants Stakes Live plant stakes shall be kept moist and installed the same day they were prepared. Live
kakawate or equivalent local species maybe used.
Bamboo Stakes
Live Plants Stakes Figure 5.25
Installation
Stakes
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5 - 17
(5)
Coco Coir Peat (Soil Conditioner) After the installation of coconut geonets, coco coir peat - soil mixture shall be distributed evenly on the net protected slope. Thumping and raking shall follow to make the mix settle underneath to ensure appropriate soil moisture and nutrients to the grasses and other planting materials.
Figure 5.26 (6)
Coco Coir Peat
Ropes Nylon rope or equivalent is used to tie cocologs to the stakes.
Figure 5.27
5 - 18
Ropes
Guidebook for Road Construction and Maintenance Management
5.4.3.2 Anchoring (1)
Common Soil The coconets shall be secured to the ground using bamboo pegs. An average of 3 pegs per square meter shall be used to ensure uniform contact and firm hold to the ground.
(2)
Compacted Soil A combination of bamboo pegs and U-shaped wire staples may be used for compacted, hard to penetrate soil. An average of 3 pegs/staples per square meter shall be used to ensure uniform contact of coco-net to the ground surface.
5.4.3.3 Vegetation (1)
Vetiver Grass Hedgerow Live hedgerow of vetiver grass (or any local suitable species) slips shall be planted on the slopes at 10 to 50 cm. interval depending on the erodibility of the soil, the steepness of the slope and the design water flow. Row distance shall likewise depend on the steepness of the slope and shall range from 1 to 4 m.
(2)
Grass cover Fast growing leguminous creeping grass shall be used on slope surfaces requiring immediate vegetation cover. It shall be applied to the soil at a rate depending on the desired density and the calculated on-site mortality rate of the plants.
(3)
Trees If trees shall be used to stabilize a slope, species that have sturdy, long and deep-penetrating roots shall be selected.
5.4.3.4 Cross Section
Figure 5.28
Typical Cross Sections for Bio-Engineering Works
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5 - 19
5.4.3.5 Installation Procedure (1)
Site Preparation -
The area shall be graded and sloped to the approved design.
-
Any water runoff control such as diversions, berms or dikes shall be completed prior to installation.
-
The face of the slope shall be smoothened and rocks, clods, vegetation (deemed detrimental to the erosion control system to be installed), and other obstructions shall be removed to ensure complete contact of the net with the soil.
-
In most cases, existing vegetation shall be retained, but shall be trimmed down to facilitate the installation of the coconet.
(2) Laying of Nets -
Installation shall begin at the top of the slope with the net laid down and securely anchored 1 m. from the edge.
-
The net shall be unrolled downslope in the direction of the water flow.
-
The edges of adjacent rolls of coir fiber nets must be spliced together using coir fiber twine ropes.
-
The coconet shall be laid loosely-not stretched- on the ground. Direct contact with the soil shall be maintained at all times.
Figure 5.29 (3)
Site Preparation
Figure 5.30
Laying of Nets
Anchoring The coir fiber net shall be secured to the ground using bamboo pegs 25 to 30 cm long. An average of 3 pegs per square meter shall be used to ensure uniform contact of net to the ground surface. For loose soils, longer pegs may be used to have sufficient ground penetration to resist pullout. U-shaped wire staples may be used for compacted, hard to penetrate soil.
(4)
Sewing There are many ways of connecting the nets together to cover the slopes but sewing
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Guidebook for Road Construction and Maintenance Management
them together is the best and most economical way of installing the nets.
Figure 5.31
Anchoring
Figure 5.32
Sewing
5.4.3.6 Planting of Grass Cover Fast growing leguminous creeping/twining grasses shall be used for slope faces requiring immediate vegetative cover. They are either hydroseeded or sowed by hand. The dominant grass in the surrounding areas can be carefully uprooted and planted on the slopes after the nets have been installed.
Figure 5.33
Hydroseeding
5.4.3.7 Watering Watering is very important especially during the early days of germination of seeds, when the roots are not established yet or when newly replanted. Upon seed germination, daily watering is necessary for a month and fifteen days for transplanted grass.
5.5 Slope Protection Structures Slope protection structures should be provided on the following conditions: *
On rippable and solid rock slopes where vegetation is not applicable.
*
On slopes which cannot be stabilized for long term by vegetation only.
*
On slope that has potential to collapse.
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5 - 21
5.5.1 Retaining Walls 5.5.1.1 Gravity Type (Concrete or Stone Masonry) These walls can sustain the earth pressure by means of its own weight and can be built more easily than the other types of retaining walls. They are often adopted when the height is relatively low (less than 4 m.) and the ground foundation has a good bearing stratum. This type of wall can be adopted also as catchwall as shown in Figure 5.33.
Figure 5.34
Gravity Type (Rock Catcher Retaining Wall)
5.5.1.2 Leaning Type (Concrete or Stone Masonry) This type of wall acts against the soil pressure not only by its own weight but also by the weight of soil as shown in Figure 5.34. Leaning Type Retaining Wall
where: Wc
Wc = Weight of Concrete Ws
Figure 5.35
Ws = Weight of Soil
Leaning Type Retaining Wall
The advantages in adopting stone masonry over concrete are that the gradient, length and horizontal alignment could be done easily to match the profile of an existing section and it is more economical. Moreover, if it will function as catch wall (with steel-framed catch fence), reinforced concrete retaining wall is advisable. Stone Masonry consists of stones with sizes as shown in Table 5.7 laid in accordance with the lines and grades as shown in the plans or as directed by the Engineer, jointed by cement mortar of 1 (cement) : 2 (sand) at trowel consistency.
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Guidebook for Road Construction and Maintenance Management
The construction steps are shown below. 1. Prepare the foundation bed, compact and moisten as per Specifications.
Mortar that is not used
2. Lay 5-10 cm thick mortar
within 90 minutes after the water has been added shall be discarded. Re-tempering
3. Embed Stones of specified size
of mortar is not permitted. Weepholes
shall
be
provided unless otherwise shown on the plans or as 4. Fill the spaces between stones with new mortar
directed by the Engineer.
5. Repeat steps 2-4 until the required dimension is attained.
Figure 5.36
Construction steps for Stone Masonry
5.5.2 Grouted Riprap Grouted riprap shall consist of the furnishing and placing of riprap with filter backing, furnished and constructed in accordance with the specification and as to lines and grades and dimensions shown on the plans. This is commonly used in slope protections, abutments, lined canals and other places called for in the plans.
(c) Figure 5.37
(d)
(e)
Surfacing
Construction steps for Grouted Riprap
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5 - 23
Grouted riprap shall be constructed in accordance with the following steps: (a) Prepare the foundation bed, compacted and
moistened
as
per
with
specifications. (b) Lay 5-10 cm thick 1:3 mortar mixture (cement 1: sand 3). (c) Embed slightly moistened stones of specified sizes into the fresh mortar. (d) Fill the voids in between the stones with mortar. (e) Repeat the above steps a until the
Figure 5.38
Grouted Riprap
specified dimensions are attained. Table 5.7 Item
Stones
Materials Requirement for Grouted Riprap and Stone Masonry Grouted riprap (Item 505） Class A: 15 kg to 25 kg Class B: 30 kg to 70 kg Class C: 60 kg to 100 kg Class D: 100 kg to 200 kg
Mortar
Stone masonry (Item 506) Thickness: 150 mm or more Width: 150% of respective thickness or more Length; 150% of respective width or more Cement (1): Sand (2)
Cement (1) : Sand (3) Class A: 300 mm Class B: 500 mm Min. Thickness As per design Class C: 600 mm Class D: 800 mm Horizontally at the lowest points, Not more than 2.0 m center to center in a staggered manner. The length Weepholes should not be less than the thickness of the walls, at least 100 mm dia. PVC is recommended. (Source: DPWH Standard Specifications for Highways, Bridges and Airports, 2013Edition)
5.5.3 Cribwall 5.5.3.1 Stone Masonry and/or Reinforced Concrete Cribwall It is a type of retaining wall particularly made up of concrete or stone masonry (or a combination of both) and supported with reinforced concrete frame. Generally, a double frame type is adopted for a 3.5 to 5.5 m. height of slope. On rock slopes with many joints or loose talus and where concrete spraying is inappropriate, concrete cribwall is advisable.
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Guidebook for Road Construction and Maintenance Management
Figure 5.39
Stone Masonry Cribwall
←Fourth Level: Stone Masonry Cribwall
←Third and Second Level: Concrete Cribwall
←First Level: Concrete Retaining Wall
←Second Level: Stone Masonry Cribwall
←First Level: Concrete Cribwall
Figure 5.40
Reinforced Concrete Crib and Pitching Wall
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5 - 25
5.5.3.2 Reinforced Concrete Frame with Vegetation Works This type is ideal for high slope composed of weathered rock or unstable soil with seepage or springs.
Figure 5.41
Reinforced Concrete Frame with Vegetation Works
Source: DPWH/JICA Technical Standards and Guidelines for Planning and Design Vol. IV, 2002 Natural Slope Failure Countermeasures
5.5.4 Gabion Wall Gabions are used where there are springs on a slope and sediments are likely to be washed out and where a collapsed portion is to be restored. The lengths should be multiples of two (2), three (3) or four (4) times the width of the gabions and the height should be 0.50 meter to 1.0 meter. The horizontal width should not be less than 1.0 meter. Gabion
Figure 5.42
Gabion Wall
furnished shall be of uniform width. Gabion wires are double twisted meshed conforming to ASTM 641 or 856 or 809. Rock pieces must be uniformly graded 100 mm to 200mm. No rock size shall exceed 2/3 the mattress depth. Filled gabions shall have a minimum density of 1,400 kg/m3. If spring water amount is big, drainage should be installed at the foot of the gabion. Filter fabric shall be placed between the slope surface and gabion materials. The filter fabric shall be rolled out into a flat non-rutted surface free from sharp objects.
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Guidebook for Road Construction and Maintenance Management
Figure 5.43
Constructed Gabion Wall at a Location with Seepage
5.5.5 Mechanically Stabilized Embankment Wall (MSE Wall) Reinforced embankment walls are of two types 1) Geotextile-reinforced and 2) Terre Armee.
Figure 5.44
Mechanically Stabilized Embankment by means of Geotextile fabrics
Road Embackment Work Embankment
Front View
9.0 m
Ground line before road slip
Collapse surface of road slip Terre Armee Wall
Bedrock
Rear View
Slip Connection Clamp Figure 5.45
Slip Bars
Mechanically Stabilized Embankment Wall (Terree Armee Wall)
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5 - 27
5.6 Rock Slope Protection As per experience, the height of bounce of rolling stone is within two meters regardless of the slope length as shown in the figure below and should be considered in designing rockfall protection works.
Figure 5.46
Relations between Rock Slope Height and Height of Bounce of Stone
5.6.1 Cutting and Removal Cutting and removal of isolated and overhanging rocks is the most effective rockfall countermeasures.
Figure 5.47
Cutting and Removal of Unstable Rock Slope
5.6.2 Shotcrete To prevent further weathering of the rock slope, shotcreting is one of the applicable measures. The following are the specified requirements for shotcreting:
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*
Weepholes shall be installed at least one for every 4 m.2 in a staggered manner.
*
Before shotcreting, wire mesh shall be laid and anchored over the face of the slope. The standard number of anchor pin is 1 to 2 per square meter. Main anchor pin shall be 16 mm diameter of 1.0 m. length, sub-anchor pins shall be 10 mm diameter of 0.3 m. length.
*
The spraying thickness of concrete is 10-15 cm. (Mortar spraying of 8-10 cm. thick is adopted as per Japan Standards.)
*
The standard mix proportion by weight of cement and aggregates shall be 1:3:1 to 1:5:2 (C: S: G) for concrete spraying. The water-cement ratio shall be 40 to 45% for concrete spraying.
Notes: *
The lower side of the convex part should be of uniform thickness.
*
To avoid clogging the weepholes, the exposed end should be capped/covered during the operation.
*
Spraying by two layers should be adopted where a lot of ruggedness exist on the surface. Wire mesh should be spread on each layer. The concrete for the second layer should be sprayed within one hour after the first layer was sprayed.
*
The work should be suspended during rain and strong wind.
Figure 5.48
Shotcrete
5.6.3 Rocknet
Figure 5.49
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Rocknet
5 - 29
5.6.4 Rock Catcher
Figure 5.50
Rock Catcher
5.6.5 Rock Shed
Figure 5.51
Rock Shed
5.7 Countermeasures for Landslide The countermeasures for landslide are mainly categorized into two types namely 1) risk mitigation and 2) structural countermeasures. The risk mitigation countermeasure is to reduce the landslide movement by means of the following: *
Slope surface drainage works
*
Underground water drainage works
*
Earth removal works (of the sliding mass head)
*
Counterweight filling works
The structural countermeasure is a prevention work by constructing structures that will resist the movement of landslide as follows: *
Pile Works
*
Shaft Works
*
Anchor Works
5.8 Provision of Underground Drainage Pipe thru Boring In case the slope is not stable due to the presence of underground water pressure,
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Guidebook for Road Construction and Maintenance Management
provision of underground drainage pipe is one of the recommended countermeasures. Underground water pressure basically increases as groundwater level increases due to rainfall infiltration as illustrated below. Therefore, it is important to conduct groundwater logging to monitor and establish the waterlevel to be applied for this method and also to verify its effect. Rainfall infiltration
Landslide Mass
level of water-table
Sliding plane
Figure 5.52
Figure 5.53
Rainfall and Groundwater Level
Typical Underground Drainage Pipe Installations
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5 - 31
5.9 Slope Stability Analysis (1)
Fellenius Method The stability of the existing slope which has a potential to slide can be analyzed by the
Fellenius method as follows:
Fs
Fr Fd
N U tan c L T
where:
Fs=
safety factor
Fr=
the sum of the resisting forces
Fd=
the sum of the driving force
W=
gravity of segment (slice)
A=
area of segment (slice)
γ=
soil density
N=
normal force by gravity, W * cos θ
T=
tangential force by gravity, W * sin θ
L=
length of sliding plane in segment
U=
pore water pressure
c=
cohesion of sliding plane
φ=
internal friction angle of sliding plane
θ=
inclination of sliding plane
T
N W
Sliding Plane
θ U
L
Figure 5.52
Fellenius Method
In case the output, Fs, is less than 1.0, the slope is evaluated as unstable. And if it is equal or greater than 1.0, the slope is evaluated as stable.
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Guidebook for Road Construction and Maintenance Management
(2)
Required Safety Factor In designing structures such as pile, shaft and anchor works against the driving force of
the landslide, necessary resisting force to be added can be estimated by the following formula.
PFs Fs
Pr T
N U tan c L P T
where:
r
Fs=
safety factor of the existing slope
Pr=
necessary resisting force to be added
PFs= required safety factor of countermeasure
Pr PFs T ( N U ) tan c L Shown in Table 5.8 are the required safety factors that were established and being adopted by Japan as their design criteria in designing landslide countermeasures. Table 5.8
Required Safety Factor for Landslide Countermeasures Condition
Rivers, railroads, national highways and/or residential area will be affected by landslide disaster, if it occurs. Prefectural roads and some houses only will be affected by landslide disaster, if it occurs. Only small village road will be affected by landslide disaster, if it occurs. Countemeasure works will be buit as temporary works only during the construction project.
Guidebook for Road Construction and Maintenance Management
Required Safety Factor PFs 1.20 1.15 1.12 1.05 to 1.10
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Chapter 6
River and Coastal Erosions
6.1 River Erosion The natural process by which the surface is worn away by the action or movement of water e.g. current from stream flow, wave, rise and fall of water – is called erosion. Along the river sides, erosion of the riverbed and banks due to stream flow or current is a common scene and likewise, damage of structure foundation due to scouring effect of the water with the eroded soil material.,
Figure 6.1
Degradation due to Riverbed Erosion
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6-1
6.1.1 Examples of Road Damages caused by River Erosion 6.1.1.1 (1)
Riverbank Erosion
Riverbank Erosions along the Bends
River Road Deposit Affected area
Figure 6.2 (2)
Riverbank Erosion along the Bend
Riverbank Erosions caused by Overflow
Over flow
Road
Debris Flow Deposit River Bed
Figure 6.3 6.1.1.2
Riverbank Erosion caused by Overflow
Riverbed Erosion
Scouring of river bed
Collapse of Gabion Wall
Insufficient depth of embedment
Note)
Sufficient depth of embedment should be
at least 2.0 m or as per result of scour analysis.
Figure 6.4
Riverbed Erosion
6.1.2 Countermeasures for River Erosion 6.1.2.1
Riverbank Protection
Table 6.1 shows applicable works to protect the riverbank and/or bed from damages due
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Guidebook for Road Construction and Maintenance Management
to river erosions. Also, shown in Figure 6.5 is a flowchart for the selection of appropriate countermeasures against river erosion. Table 6.1 Countermeasure
Countermeasures against River Erosions
Types of Work Slope Pitching Work (Boulder/Riprap, Brick, Conrete, Concrete Block) Gabion (Cylinder, Mattress)
Riverbank Revetment Works
Stone Masonry Concrete Retaining Wall Piling (Steel ,Concrete) Bed Pitching Work (Boulder/Riprap, Brick, Concrete, Concrete Block)
Riverbed Protection Works
Block Pitching Gabion (Cylinder,Mattress) Groundsill/Check Dam Floodway, Dredging
Rechanneling Spur Dike
START
Small (>5.0m)
Effect of erosion on road (Distance between Road/River)
Large (≦5.0m)
Location of erosion
Temporary work
Both of riverbank/riverbed
Riverbank
- Wire cylinder - Gabion revetment - Wicker revetment - Timber crib consolidation
Figure 6.5
- Masonry revetment - Concrete revetment - Concrete block revetment
- M asonry revetment - Concrete revetment - Concrete block revetment - Check dam - Concrete consolidation - Concrete spur dike
Riverbed
- Check dam - Concrete consolidation - Concrete spur dike
Selection of River Erosion Countermeasures Flowchart
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6-3
(1) River Revetment Works River revetment works are commonly adopted on riverbank and slope as a countermeasure against erosion as shown in Figure 6.6 Bank line before river erosion
Stone masonry revetment
Road
Road
Soil slope
Rock slope
Rock slope Backfill
River erosion a) Section View of River Erosion
Road
b) Section View of Revetment
Road
Backfill
Road
Backfill Wire cylinder
Steel sheet pile a) Stone Massonry
b) Inverted T-type Concrete Wall
Figure 6.6
c) Concrete Sheet Pile
Types of Revetment Works
In order to protect the river and road slope from erosion by water infiltration and/or scouring, revetment works shall be provided. Prior to planning and designing, preliminary investigations covering the following; river erosion, history, longitudinal and cross sections, gradient,slope, bank geology and proximity locations should be conducted to determine the exact location and appropriate type of revetment. Figure 6.7 shows a flowchart of design procedures for river revetments. The following parameters such as roughness of the riverbed, velocity of river flow and slope/gradient of the riverbank are important factors to consider in the design.
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Guidebook for Road Construction and Maintenance Management
START ↓ River and geological surveys ↓ Preliminary planning: - Location, cross and longitudinal sectional details - Alignment of river and revetment - Height of revetments ↓ Selection : - Flow velocity and slope gradient. ↓ Design
-Design load computation - Stability Analysis of river slope/bank (overturning, tensile stress, sliding, bearing capacity of foundation) - Structural design computation ↓
Design of foundation - Consolidation ,settlement and scouring analysis of foundation - Footing protection works ↓ END Figure 6.7
Design Procedure for River Revetment Work
Shown below is a typical section of river revetments works. a b
Road
Road
Weep hole H: V=0.5:1
a=0.20m
Design riverbed
b=0.35m H: V=0.4:1
a=0.20m b=0.10m
b a c
Body
filling
H: V=0.3:1 concrete Design riverbed
b=0.35m H: V=0.2:1
Backfill
2.0 m
Backfill
Stone masonry
Figure 6.8
2.0 m
Concrete block masonry
Typical Cross-section of Revetment Works
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6-5
(2) Concrete Block Slope Pitching Concrete block pitching work can be designed as grouted riprap. Basically, large and heavy concrete blocks are more stable against strong river current and generally designed for workability. However, in case the laying is done manually, the weight of the block should be considered. Concrete block of 400mm (width) x 400mm (length) x 100mm (thickness) which weighs about 36 kgs. is used wherein the river flow design velocity is 3.5 m/s or less.
Figure 6.9
6-6
Laying of Concrete Blocks on River Slope
Guidebook for Road Construction and Maintenance Management
6.1.2.2
Riverbed Protection Works
Although there are different types of riverbed protection works, groundsill (head and/or non-head type) is popularly used. Sample arrangement of groundsills is shown in Figure 6.10. River flow
River flow
Road
Road Riverbed erosion Potential bank collapse due to riverbed erosion Groundsills
b) Plan View of Groundsill Arrangment
a) Plan View of River Erosion
Figure 6.10
Sample Arrangement of Groundsills
Figure 6.11 shows a typical section of groundsill. Groundsills regulate the flow of water to prevent the occurrence of scouring velocity that would damage the riverbed.
Head Type
Non-head Type
Flow direction Design flood level Existing riverbed
Figure 6.11
Typical section of Groundsill
Groundsills function to stabilize the riverbed as follows: 1.
Decrease the scouring force of water flow for the stabilization of the riverbed in the upstream side (Head Type).
2.
Prevent the scouring and degradation of the riverbed (Non-head Type).
3.
Ensure the stability of revetment foundations (Both types).
Its right location and arrangement should be determined taking into consideration,
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6-7
among others, the following: 1.
Sections with riverbed erosion or degradation.
2.
Sections immediately downstream and on the same side of the collapsed riverbank.
3.
The downstream area of the structures to be protected.
In case the damaged portions and banks or scoured areas are vast, several groundsills should be installed. Figure 6.12 shows a flowchart of design procedures for groundsill. The following parameters such as roughness of the riverbed, velocity of river flow and slope/gradient of the river are important factors to consider in the design.
START ↓ River and geological surveys ↓ Preliminary planning: - Location, cross and longitudinal sectional details - Alignment of groundsills - Height of groundsills ↓ Selection of type: - Consider flow velocity and slope gradient ↓ Design: -Design load computation -Stability Analysis of groudsills (overturning, tensile stress, sliding, bearing capacity of foundation) -Structural design computation ↓ Design of apron and side wall ↓ END Figure 6.12
Design Procedure for Groundsill
The position of groundsill should be linear and at right angle to the direction of the water flow as shown in Figure 6.13.
6-8
Guidebook for Road Construction and Maintenance Management
A
B
C
D
Flow Flowingdirection direction
Figure 6.13
Arrangement of groundsills relative to the direction of flow
A detailed drawing of groundsill is shown below: B Design flood level
H=height of groundsill body (m)
H1 H
b
Height of groundsill
1:m
1:0.2
h1
B=Thickness of crest opening (m) H1=Height of fall (m) h1=Overflow depth (m) b=Embedment depth of main body (m) m=Upstream slope of groundsill
Figure 6.14
Details of Groundsill
The depth of embedment is the most important factor for the stability of groundsill (refer to the table below).
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6-9
Table 6.2
Required Depth and Width of Groundsill Symbol
Part of Groundsill
(See
Condition of Foundation Sand and gravel
Soft rock
Hard rock
B
1.5 to 2.0 m
1.5 to 2.0 m
1.5 to 2.0 m
b1
2.0 m or more
1.5 m or more
1.0 m or more
b2
2.0 m or more
1.5 to 2.0 m
1.0 m or more
Width of Wing (Bottom)
b3
2.0 m or more
1.0 m or more
0.5 m or more
Depth of embedment of Wing
b4
1.0 m or more
0.5 m or more
0.5 m or more
Depends on
1.0 : 2.0
1.0 : 2.0
Excavation Line
(H : V)
(H : V)
Fig.)
Depth of Embedment (Main Body) Width of Wing (Top) Embedded Width of Wing (Top)
Inclination Degree of Wing Edge
m
Note: Refer to Figure 6.16
Figure 6.15 6.1.2.3
Typical Section of Groundsill
Rechanneling
Rechanneling is considered as a countermeasure against riverbank and riverbed erosions. The concept of this countermeasure is shown in Figure 6.16
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Guidebook for Road Construction and Maintenance Management
River flow Road
River flow Road
Potential bank collapse New channel by excavation
a) Plan View of River Erosion
Figure 6.16
b) Relocation of channel
Rechanneling Concept for Riverbank and Riverbed Protections
Construction of spur dike is also an effective countermeasure against riverbank and riverbed erosions. Spur dike change the river flow direction to protect river bank and also controls sedimentation of the riverbed. There are three types of spur dikes namely; 1) perpendicular; 2) upward and 3) downward- as shown in Figure 6.17. For riverbanks, upward spur dike is recommendable. For reference, shown in Figure 6.18 is a typical cross-section of spur dike.
Figure 6.17
Type of Spur Dike
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6 - 11
Low Crest Type
High Crest Type
W: river width Lspur: Length of spur dike Flow Deflector Figure 6.18
6 - 12
Hspur: Height of Spur dike
Typical Cross Sections of Spur Dike
Guidebook for Road Construction and Maintenance Management
6.2 Coastal Erosion At sea front on coastal areas, earth surface is worn away by wave and wind actions which instantaneously change the configuration of the surrounding areas after typhoon that generates big waves. The rise and fall of water known as tide continuously and gradually changes the sea bed configuration due to the influence of under current and littoral transport activities. Basically, waves and surges mainly cause the damages on coastal road. There are three cases; 1) scouring of foundation; 2) washout of backfill materials 3) collapse of the main body.
Figure 6.19
6.2.1
Examples of Road Damages caused by Coastal Erosion
Case 1: Scouring of Foundation
Figure 6.20 illustrates the collapse of coastal revetment due to the scouring of the foundation bed. Waves and surges scour the foundation bed which triggers the collapse of the revetment.
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Over Flow Erosion
Over Flow Road Wave
Wave
Road
Erosion
Figure 6.20 (a) Road Body Collapse
Collapse of Coastal Revetment (b) Slope Revetmentdue Slip to Scouring of Foundation Bed Road
Roadside
Collapse of Grouted Riprap Not so Eroded High Water Level ↓ Outflow of behind materials Eroded Portion Average Sea Level Sea
Figure 6.21out of Backfilling Conceptual Diagram of Scouring of Foundation Bed (c) Wash Material
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High Tide Level : +1.0 m ~ 1.7 m
Figure 6.22
Collapse of Coastal Revetment
6.2.2 Case 2: Washout of Backfill Materials Washing out of backfill materials also cause the collapse of coastal revetments as illustrated in Figures 6.23, 6.24 and 6.25.
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6 - 15
Figure 6.23
Collapse of Coastal Revetment due to Washout of Backfill Materials
Inside this line, materials are not grouted well.
This portion, filling materials are not grouted well.
Collapse inside the Masonry
RoadsideRoad
Masonry and backfill materials are not grouted and compacted well.respectively.
Figure 6.24
Figure 6.25
Washout of Backfill Material
Collapse of Coastal Revetment due to Washed out Backfill Material
The water overtopping the revetment accelerates the displacement of backfill materials as explained below:
6 - 16
1.
Wave surge overtops the revetment and then scours the road shoulder.
2.
Water infiltrates into the backfill and washes it away.
3.
Cracks are then generated on the revetment.
Guidebook for Road Construction and Maintenance Management
Top Left: Wave surge scours the shoulder. Top Right: Scoured portion progresses down to the backfill materials. Bottom Left: The revetment then collapses. Figure 6.26
Collapse of Coastal Revetment due to Overtopping
6.2.3 Case 3: Collapse of Mainbody Big wave surge can erode the concrete surface. Figure 6.28 shows the eroded surface of grouted riprap.
Levels of erosion at the upper, middle and
Upper: Lightly eroded.
lower portions.
Middle: Moderately eroded. Figure 6.27
Lower: Heavily eroded.
Levels of Erosion of Grouted Riprap Surface
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6 - 17
Consequently, cracks will develop on the revetment.
Insuffient grouting cannot withstand wave surge
Inadequate thickness of concrete surface
Cracked and broken concrete surface. Figure 6.28
Collapsed Revetment due to Progression of Cracks
6.2.4 Countermeasures for Coastal Erosion Countermeasures to be applied are similar to that of river bank protection. Design strategies for countermeasures are shown below. Table 6.3
Countermeasures for Coastal Erosion
Cause of Damage
Countermeasure
Erosion of foundation bed
Provide adequate depth of embedment.
Washout of backfill
Backfill and cover with concrete slab, joints shall be properly
materials
sealed.
Collapse of mainbody
Appropriate structure shall be selected. Basically, riprap is not advisable.
Coastal slope revetments are provided to prevent road bank erosion from the impacts of waves, flood tides and tsunami. Figure 6.30 illustrates a conceptual design for coastal slope revetment commonly and widely used. The revetment shall be designed for the following purposes:
6 - 18
•
To minimize the impact of seawater due to flood tide or tsunami,
•
To reduce overtopping by waves, and
Guidebook for Road Construction and Maintenance Management
•
To prevent erosion due to wave action. Recurved Parapet C L
ROAD
Wave Breaking Side Drain Ditch Foot Protection
Waterside Slope Revetment Foundation
Figure 6.29
Conceptual Design of Coastal Slope Revetment
Generally, coastal revetments are composed of a slope revetment, foundation, foot protection, wave breaker and curved parapet wall, which are required in consideration of the tidal level, wave force and sub-soil ground condition and should be accounted for in the design. Shown in Figure 6.30 is a flowchart for the selection of countermeasures against coastal erosion.
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6 - 19
START
Not Large
Large
Affect of erosion to road or behind area
Damage level (Impact to road body)
Serious Impact
Caused of damage Not Serious Impact
- Repairing Work - Restoration of damage section - Regular inspection and maintenance
Not enough strength of revetment structure
- Revetment work - Foundation work - Wave breaking work
Scouring at slope toe portion
- Foot protection work - Foundation work - Water cut-off work
Washing out backfilling material
Overflowing wave
Figure 6.30
- Revetment work - Foundation work - Water cut-off work
- Recurved parapet work - Wave breaking work
Selection of Countermeasures Against Coastal Erosion
As to the types of damages, the following describes basic countermeasure requirements. a)
Not enough strength of slope revetment to withstand wave force *
Reconstruct slope revetment and foundation to meet the technical requirements.
*
Install wave breakers to reduce wave force that will act on the surface of the slope revetment.
b)
6 - 20
Scouring at toe by wave force *
Ensure that the required embedment depth of the foundation is provided.
*
Provide foot protection on the toe or in front of the foundation.
Guidebook for Road Construction and Maintenance Management
Embedded Depth
Wall Thickness
Sheet Pile
(a) by Concrete Wall
Figure 6.31 c)
(b) by Sheet Pile
Typical Foundation Cut-off Wall
Scouring at the toe by seepage water *
Replace the backfill materials of the revetment and/or embankment material with impermeable materials.
*
Ensure the required embedment depth of the foundation is provided and/or provide water cut-off wall.
d)
Washing out of backfill material *
Replace revetment with water-proof structure.
*
Replace backfill material of the revetment with impermeable materials.
*
Ensure that the required embedment depth of the foundation is provided and/or provide water cut-off wall
e)
Wave surge overtopping *
Install wave breakers in front of the revetment slope.
*
Provide a curved parapet wall connected to the existing revetment body.
*
Weep holes shall be installed.
*
Carriageway and shoulder at shoreline shall be paved with cement concrete.
As shown in Figure 6.32, for construction of coastal revetment, the following should be considered. 1.
Behind/ inside the masonry, filling materials should be compacted/ grouted well.
2.
Enough depth of foundation should be provided.
3.
Road shoulder should be paved with concrete.
4.
Weepholes should be placed in appropriate position to drain overtopped water.
Guidebook for Road Construction and Maintenance Management
6 - 21
3. Road shoulder should be paved with concrete 1. Behind/inside the masonry, filling materials should be compacted/ grouted well
Shoulder
Road
2. Enough depth of foundation should be provided
Figure 6.32
6 - 22
Considerations for Coastal Revetment Design
Guidebook for Road Construction and Maintenance Management
Chapter 7
Road Safety
7.1 Road Signs Road signs contain instructions that the road user is required to obey. These provide warning of hazards that may not be self-evident and information about directions, destinations and points of interests. Also, since signs are essential part of the road network system, the information provided should be concise, consistent and most importantly, these should be installed at conspicuous or designated spots along the roadway. Moreover, prior approval of the DPWH Secretary or the Head of the Office concerned for the installation of the same should be sought. No road signs shall bear any advertising or commercial message, or any other messages that are not essential to traffic control. Placement of unauthorized signs within the road right-of-way or close to the roadway is not allowed. The display of unofficial and non-essential sign is likewise not permitted.
7.1.1 Classifications Road signs are classified as follows: Type R
Regulatory Signs
Type W
Warning Signs
Type G
Guide or Informative Signs
Type S
Instructional Signs
Type HM
Hazard Markers
(1)
Regulatory Signs (Type R) Regulatory signs indicate the application of legal or statutory requirements, e.g. obligation to give way at intersections, speed limits, prohibition of movements at intersections and control of parking of vehicles. Most regulatory signs are circular in shape with white inscriptions and either red or blue background as shown in Fig. 7.1 The notable exceptions to this are STOP (octagonal), GIVE WAY (triangular) and some manually operated banners used in road works. It is important that these shall be removed promptly if the legal requirements become inconsistent with the present conditions.
Guidebook for Road Construction and Maintenance Management
7-1
Priority Direction Figure 7.1 (2)
Regulatory Signs (Type R)
Warning Signs (Type W) Warning signs notify road users of the condition on or adjacent to the road that may be unexpected or hazardous. Should not be used if, under normal conditions, the driver can see the potential hazard ahead.
Figure 7.2 (3)
Warning Signs (Type W)
Guide or Informative Signs These inform and guide the road users of directions, distances, locations of services and points of interests.
Figure 7.3 (4)
Guide or Informative Signs (Type G)
Instructional Signs (Type S) These are used at locations where ordinary guide or regulatory signs do not achieve
7-2
Guidebook for Road Construction and Maintenance Management
the desired results. Also, these guide motorists of the direction or follow a course of action.
Figure 7.4 (5)
Instructional Signs (Type S)
Hazard Markers (Type HM) These are used to emphasize a marked change in the direction of travel and the presence
of an obstruction.
Figure 7.5
Hazard Markers (Type HM)
7.1.2 Standard Application Uniformity of application is as important as standardization with respect to design and placement. Identical conditions should always be treated with the same type of signs so that road users can readily anticipate the course of action required. Basic requirements for road signs are as follows: 1.
Fulfill a need
2.
Command attention
3.
Convey a clear, simple message
4.
Command respect
5.
Give adequate time for proper response
Guidebook for Road Construction and Maintenance Management
7-3
7.1.3 Design Uniformity in the design facilitates easy identification by the road user. Standardization of shape, color, dimensions, inscriptions and illumination or reflectivity is important so that various classes of signs can be easily recognized. The following design principles are considered: *
The driver should not be distracted by a road sign from his driving.
*
Road signs should be understood by the driver traveling at any given speed and must have sufficient time to take appropriate response safely.
Note: For necessary details, please refer to DPWH Road Signs and Pavement Markings Manual, February, 2012 Edition and DPWH Road Safety Manual, 2012 Edition.
7.2 Weighbridge Station National roads and bridges are damaged by freight trucks and trailers whose gross weights exceed the allowable limits. In line with this, DPWH has installed weighbridge stations at strategic locations along national roads.
Figure 7.6
Weighbridge Stations
Shown in Table 7.1 is the Maximum Allowable Gross Vehicle Weight (GVW) based on the maximum allowable axle loads of 13,500 kgs as per Republic Act No. 8794.
7-4
Guidebook for Road Construction and Maintenance Management
Table 7.1
Maximum Allowable Vehicle Weight
MAXIMUM ALLOWABLE GROSS VEHICLE WEIGHT (GVW) PER RA 8794 (REVISED 2012)
Note: Special Permit to Travel shall be required for vehicles loaded with inseparable/or special cargoes exceeding the corresponding GVW and vehicles with configuration different from those shown in the above matrix.
Guidebook for Road Construction and Maintenance Management
7-5
7.3 Road Warning System For reference, an example of Road Status and Information System is shown in Figure 7.7. This can be accessed thru the DPWH Website.
Figure 7.7
7-6
Road Status and Information System
Guidebook for Road Construction and Maintenance Management
Chapter 8
Monitoring and Investigation
8.1 Weather Monitoring 8.1.1 Rain Gauges To obtain rainfall data and provide road users with rainfall information, rain gauges are installed and utilized. There are two types 1) standard rain gauge and 2) weighing precipitation gauge (self-recording type). Figure 8.2 illustrates the standard rain gauge and the rainfall is measured manually as shown in Figure 8.1. Figure 8.3 illustrates the weighing precipitation gauge which measures the rainfall by mass automatically. Generally, both types of rain gauges should be installed at the same location in order to avoid missing data in case one does not work well.
Figure 8.1
Figure 8.2
Manual Data Collection from a Standard Rain Gauge
Standard Rain Gauge
Figure 8.3
Weighing Precipitation Rain Gauge
Guidebook for Road Construction and Maintenance Management
8-1
8.1.2 Weather Station The main purpose of a weather station is to give notice to the public of the current weather conditions such as rainfall, temperature, wind direction and speed. Weather data repository is important in setting up warning criteria. It is useful particularly in construction management since scheduling of works can be made by knowing the forecast weather condition. Weather station should be installed in a place where there is no obstruction for accurate data collection. Solar battery and micro wave data connection
Data logger and data repository to computer Figure 8.4
Weather Station
8.2 Visual Inspection of Pavement 8.2.1 ROCOND ROCOND is a visual road condition assesment system which includes a manual entitled Visual Road Condition Assessment Manual Vol. 9. ROCOND was designed mainly to provide road condition data for Pavement Management System (PMS) and also for Routine Maintenance Management System (RMMS). Therefore, ROCOND functions also as a part of Asset Management System and Database System in DPWH. Currently, DPWH intends to develop a mechanized system for road inspection such as International Roughness Index Testing Vehicle and/or Road Condition Survey Vehicle. When this system is completed, this will be utilized in addition to ROCOND.
8.2.2 Portable Falling Weight Deflectometer (FWD) (1)
Applicable Scope This apparatus is used for the evaluation of subgrade reaction, subbase and base course elasticity. However, it is not applicable with foundations having gravel or stone of size 3.3 cm. or more.
8-2
Guidebook for Road Construction and Maintenance Management
(2)
Measurement method 1)
Prepare a smooth and level surface. Remove loose material. If surface is rough and hard, fill with sand for leveling.
2)
Set the equipment to level and confirm by a spirit level. Figure 8.5
Figure 8.6 3)
Setting up of FWD
The Drop Rig
Initially drop the weight 5 times from about 10 or 15 cm height prior to testing.
4)
Connect main body and the display.
5)
Turn on the display instrument. Refrain from touching the main body until the standby window appears on the display. The instrument conducts initial measurement automatically.
Figure 8.7
The Mainbody and
Display Instrument 3
6)
Push
CONDITION
＜＜Ｐａｒａｍ．＞＞
at standby mode and input
diameter of load plate (100 mm only available), estimated Poisson’s ratio
Ｄｉａｍｅｔｅｒ Ｐｏｉｓｓｏｎ‘ｓ Ｆ－Ｎａｍｅ Ａ０００
１２：００：００ φ １００ ０．３００
．ＣＳＶ
ｍｍ
Ｎｏ．００
and file name. Table 8.1 shows how to evalue Poisson's ratio.
Guidebook for Road Construction and Maintenance Management
Display
8-3
Table 8.1 N-Value by standard penetration test (times/30cm) 0 to 8 8 to 15 15 or more 0 to 10 10 to 20
Nd-Value by dynamic cone penetration test (times/10cm) 0 to 10 10 to 20 20 or more 0 to 5 15 to 30
Slightly dense
20 to 30
30 to 45
0.35
Moderately dense
30 to 50
45 to 75
0.30
Soft-medium Stiff Very Stiff Loose Medium
Finegrained soil
Sand
Very dense -
Rock 7)
Poisson's Ratio
Poisson’s Ratio
0.45 0.40 0.35 0.40 0.35
50 or more 75 or more (Source: Japan Tunnel Design Standard)
0.30 0.25
Conduct initial measurement as follows: Push buttons in the order of
5 MONITOR
Ｆ３
,
/BAL (Balance).
Confirm that the Arabic numerals on the windows are almost 0 as shown below: ＜＜Ｍｏｎｉｔｏｒ＞＞ １２：００：００
＋ ＋ Ｐ０／Ｄ０
５０ ０．１
Ｎ
ｍ／Ｓ２Ｐ ＢＡＬ
To return to stanby mode push
＜＜Ｍｏｎｉｔｏｒ＞＞ １２：００：００
＋ ＋ Ｐ０／Ｄ０
ESC
０ ０．１
Ｎ
ｍ／Ｓ２Ｐ ＢＡＬ
.
４
8)
Push
MEAS.
at standby mode, drop the weight and confirm Displacement and
Modulus of Subgrade Reaction as a preliminary test. Ａ０００
１２：００：００ Ｐ０ Ｄ０ Ｋ－ＴＭＬ Ｎｏ． ［Ｎ］ ［ｍｍ］［ＭＮ／ｍ３ ］ ０４ ６７５４ ０．５００ ７５ ０３ ６７５４ ０．５００ ７５ ０２ ６７５４ ０．５００ ７５ ０１ ６７５４ ０．５００ ７５ Ｍｏｎｉ． Ｃｏｎｄ． Ｎｅｘｔ
Figure 8.8
8-4
P0: Load [N] D0:Displacement [mm] K-TML:
Modulus
of
Subgrade
Reaction by TML type FWD-Light [kN/m3]
Measure Display of Portable FWD
Guidebook for Road Construction and Maintenance Management
In case of evaluation on Subgrade Reaction by using of 100 mm diameter plate, required displacement is 0.417 mm. Try droping with various heights of weight until you attain the required displacement. If the displacement is 0.417mm or more when 5cm height or less applied, stop this preliminary test and replace the load plate with a bigger size. When 300 mm diameter load plate is used, standard level of displacement shall be 1.25 mm. In case other diameter load plate is utilized, specific displacement can be estimated by the following formula, SDL = 1.25 x (Di/300). Where, SDL = Specific displacement level (mm), Di = Diameter of load plate (mm). Required displacement level of each diameter of load plate is summarized in Table 8.2. Table 8.2
Specific Displacement Level for FWD
Diameter of load plate
Required displacement
Allowable gravel size
(mm)
(mm)
(mm)
100 mm
0.417
less than 33mm
150 mm
0.625
less than 50mm
200 mm
0.832
less than 66mm
300 mm
1.250
less than 100 mm
9)
Find a testing drop height of weight for main test as shown inTable 8.3. Table 8.3
Drop Height of Weight for Main Test Drop height of weight for main test
Status
1st stage
2nd stage
3rd stage
X- 5cm
X cm
X+5 cm
X-10cm
X cm
X+10cm
5cm
10cm
15cm
Approximate drop height to obtain specific displacement is X cm, and K-TML: elastic modulus on displaying installment is 50 MN/m3 or less Approximate drop height to obtain specific displacement is X cm, and 3
K-TML: elastic modulus is bigger than 50 MN/m 5cm drop of weight get the displacement of 0.417mm or more, stop the preliminary test. 10) Push
at standby mode, drop the weight and confirm Load and
Displacement (Main Test).
Guidebook for Road Construction and Maintenance Management
8-5
Conduct six times drops of each stage of drop height. If you have some failures, additionaly drop again up to you get six appropriate results. After dropping, push
to trigger waiting status. Record the load and
displacement in FWD-Light Test Recording Sheet. 11) Analyze main test data Input main test data into FWD-Light Analysis Sheet. The sheet calculates engineering properties of the ground as shown in Figure 8.9. Measurement of load and displacement
Modulus of Subgrade reaction of Portable FWD : KP.FWD (MN/m3) and/or (pci) a) Modulus of Subgrade Reaction, Equivalent to 30 inch (76.2 cm) diameter plate static load test: K30inch (MN/m3) and/or (pci) Figure 8.9
Elastic modulus of Portable FWD: EP.FWD (MN/m2) and/or (psi) b) Site CBR (%) c) Design CBR (%)
d) Unconfined Compression Strength: qu (MN/m2) and/or (psi)
Estimated Engineering Property
Estimation Necessary values for design can be estimated or converted from the test data as follows: a)
K30inch = K P.FWD/(0.260* K P.FWD0.373)/2.54 K30inch, K P.FWD in MN/m3
b)
Site CBR (%) = EP.FWD/10, experimentally
c)
Design CBR =( Average Site CBR) - ( standard deviation) CBR in %
d)
qu = EP.FWD/250, experimentally qu, EP.FWD in MN/m2 and/or psi (Source: Abe Nagato 2003, Japan Pavement Journal)
8-6
Guidebook for Road Construction and Maintenance Management
Portable FWD Analysis THE PROJECT FOR IMPROVEMENT OF QUALITY MANAGEMENT FOR HIGHWAY AND BRIDGE CONSTRUCTION AND MAINTENANCE Job Title January 9, 2009 Weather Cloud Test Date KM. 280 +380 Test Location TUBLAY, KAPANGAN & KIBUNGAN Test Point Poisson's ratio Gravelly Soil 0.35 Weight Mass 5 kg Soil Type Load Plate Diameter 150 Inspector Mikihiro Mori mm Drop Height of 3rd Stage 30 cm Modulus of Elastic Modulus of Load Displacement Load Stress Subgrade Reaction No. Portable FWD of Potable FWD Ｋp.FWD （MN/m3） Ｅp.FWD （MN/m2） N mm kN/m2 7639 0.571 432 379 100 1 7636 0.573 432 377 99 2 7628 0.574 432 376 99 3 7671 0.600 434 362 95 4 7624 0.598 431 361 95 5 7663 0.595 434 364 96 6 7644 0.588 433 368 97 Average Drop Height of 2nd Stage 40 cm Modulus of Elastic Modulus of Load Displacement Load Stress Subgrade Reaction No. Portable FWD of Potable FWD Ｋp.FWD （MN/m3） Ｅp.FWD （MN/m2） N mm kN/m2 8352 0.610 473 387 102 1 8395 0.606 475 392 103 2 8392 0.611 475 389 102 3 8401 0.627 475 379 100 4 8382 0.622 474 381 100 5 8413 0.636 476 374 99 6 8397 0.620 475 383 101 Average Drop Height of 50 cm Modulus of Elastic Modulus of Load Displacement Load Stress Subgrade Reaction No. Portable FWD of Potable FWD Ｋp.FWD （MN/m3） Ｅp.FWD （MN/m2） N mm kN/m2 9139 0.687 517 376 99 1 9195 0.661 520 394 104 2 9187 0.665 520 391 103 3 9203 0.662 521 393 104 4 9220 0.667 522 391 103 5 9231 0.655 522 399 105 6 9207 0.662 521 394 104 Average
Displacement－Load Stress Chart
0.59 0.62 0.66
1000
Load Stress （ｋN/m 2）
900
433 475 521
0.625 mm Displacement 8448 N Load Stress of 0.625 mm Displacement 478 kN/m2 Load of
97 101 104
800
7644
700
8397
382 MN/m3 Modulus of Subgrade Reaction,
9207
Equivalent to 30 inch diameter plate
600 500
-266
400
Modulus of Subgrade Reaction ＫＰ．ＦＷＤ
static load test : K 30inch 63
-1
MN/m3
Elastic Modulus of Potable FWD :EP.FWD
300
MN/m2
101
200
Estimated CBR by Elastic Modulus, 2
CBR(%) = EP.FWD/10 (MN/m )
100
10
0 0
0.5
1 Displacement （mm）
1.5
2
qu (MN/m2) = EP.FWD/250 (MN/m2)
0.40
Figure 8.10
%
Estimated unconfined compressive strength
MN/m2
Example of Analysis Sheet for Portable FWD
Guidebook for Road Construction and Maintenance Management
8-7
8.3 Slope Investigation 8.3.1 Measurement 8.3.1.1
Visual Measurement
The slope height and angle can be estimated roughly by using a tape measure and a range pole as shown in Figure 8.11.
Figure 8.11
Rough Determination
of
Slope
Height and Angle 8.3.1.2
Portable Laser Distance Meter
Profile survey using portable "Laser Distance Meter" is recommended for the evaluation of road slope condition as shown in Figure 8.12. The range of capability is 10 to 300 meter distance.
Figure 8.12
Road Slope Survey by Digital Distance Meter
Figure 8.13
8-8
Digital Distance Meter
Guidebook for Road Construction and Maintenance Management
8.3.2 Visual Slope Investigation 8.3.2.1
Important Tips on Slope Investigation
Visual slope investigation should be conducted from a distance with the
Many cracks
aid of topographic maps and aerial
can be seen
photographs or satelite images to grasp an overall situation of the target
Observation from a Distance
slope as shown in Figure 8.14. Then field reconnaissance survey should be carried out to obtain a detailed condition of the slope. In addtion to this, the slope shall be observed from top to bottom during the field reconnaissance as Figure 8.14
shown in Figure 8.15.
Visual Slope Investigation (1/2)
Easy to identify
Difficult identify
Easy to identify
to
X
X
Open cracks caused by toppling
Figure 8.15 8.3.2.2
Open cracks caused by sliding
Visual Slope Investigation (2/2)
Geophysical Feature
Figure 8.16 and 8.17 illustrate the terms and definitions utilized in Slope Investigations.
Guidebook for Road Construction and Maintenance Management
8-9
Lc: Length of Surface D: Total Length L:
Depth of Displaced Mass
Vc: Vertical Height of Surface of Rapture Hc: Horizontal Distance of Surface of Rapture
(Source: Varnes, 1978) Figure 8.16
Block Diagram of Complex Earth Slide/Earth Flow
(Source: Japan Landslide Association) Figure 8.17 8.3.2.3
Typical Configuration and Phenomena of Earth Slide
Checklist for Slope Investigation
Figure 8.18 shows important locations to be investigated. Check the boundary with natural slope
Check the deformation of the upper portion of the slope shoulder
2 1 2 1
Observe swelling, water seepage etc. Check a void by hammer sounding
Figure 8.18
8 - 10
Check overall status, sketch and take photos
Important Locations for Slope Investigation on Cut Slope
Guidebook for Road Construction and Maintenance Management
8.3.3 Digital Clinometer Clinometer is an apparatus used for geological reconnaissances and surveys. It can measure Strike and Dip. Strike and Dip are geological words which means a direction, a point of compass, and an inclination of plane, slope or stratum as illustrated in Figure 8.19.
strike
Surface of slope /geological layer
Directio n of dip
Angle of dip
Horizontal plane
Figure 8.19
Strike and Dig
Analog type of Clinometer as shown in Figure 8.20 (Left) used to utilized but Digital Clinomete is popularly utilized currently.
Analog Clinometer
Digital Clinometer (Geo Clino) Figure 8.20
Clinometer
Wait for a while till the oscillation of the needle of compass stops in case of Analog Clinometer. But Strike and Dip of inclined plane are displayed instantly in case of Digital Clinometer.
Guidebook for Road Construction and Maintenance Management
8 - 11
8.3.3.1
Name of Parts
Mainbody
Display Figure 8.21
8.3.3.2
Parts of Digital Clinometer
Usage Figure 8.22 shows the usage of Digital Clinometer.
Step 1
Step 2 Step 1:
Set the clino plate.
Step 2:
Place the GeoClino on the plate to
measure Strike. Step 3:
Place the GeoClino on the plate to
measure Dip. Step 3 Figure 8.22
8 - 12
Usage of Digital Clinometer
Guidebook for Road Construction and Maintenance Management
(1)
Power-ON/OFF Keep pressing "POWER Button" more than 1 second to power on.After the power is on, keep pressing "POWER Button" more than 1 second to power off.
(2)
Mode of Measurement: There are three modes of measurement.
PLANE
mode is to measure the strike and the dip of the bedding plane (or any other surface) automatically by simply placing GeoClino onto the plane.
LINEATION
mode is to measure trend and plunge of a lineation and simultaneously the strike and the dip of the plane on which the lineation lies.
MANUAL
mode is to measure the orientation of the plane and lineation separately, with higher resolution.
The method to change a mode is as follows: Keep pressing "SET Button" more than 1 second to show the Setting Menu display. Move the cursor to 1.MEASURE MODE. And press "SAVE Button" or "HOLD Button". Move the cursor to 1.[PLANE], 2.[LINEATION], or 3.[MANUAL], and press "SAVE Button". (3)
Measuring in PLANE mode Place the back of GeoClino onto the bedding plane (or else) in any direction. The strike and dip of any surface of any orientation are measured automatically. Measured data come up digitally on display. P shows PLANE mode, followed by number of measurement, then date and time in the upper line, the strike and dip on the lower line. Accuracy of dip is low in PLANE mode. Use MANUAL mode for higher accuracy.
Guidebook for Road Construction and Maintenance Management
8 - 13
(4)
Measuring in LINEATION Mode Place the back of GeoClino on a bedding plane (or else) and align the longer edge onto a lineation, with the arrow on upper right of GeoClino to the plunging direction. Measured
data
come
up
on
display
automatically. L shows LINEATION mode, followed by number of measurement, then date and time in the upper line. Next come the strike and dip of the bedding plane on which the lineation lies, followed by the trend and plunge of the lineation in the lower line. Read as the plane strikes in N 24°E with dip 41°to W, the trend of lineation is N 68°W with the plunge of 40°, for example. (5)
Measuring in MANUAL Mode Use this mode to measure strike and dip of a bedding plane (or else), and trend and plunge of a lineation separately. (a)
To measure strike and dip of a plane Place the back of GeoClino onto the bedding plane. Rotate GeoClino to make the long
Green Level light (2)
edge horizontal, keeping the back on the plane, until the plunge becomes zero. Green Level light (2) is turned on when the plunge becomes zero. Strike and dip of the plane are on display. On display, M shows MANUAL mode
followed
by
number
of
measurement, then date and time in the upper line, and the strike and dip of the surface in the lower line. Plunge is of course 0. Read as strike in N 34° E and dip 38° to W, for example.
8 - 14
Guidebook for Road Construction and Maintenance Management
(b)
To measure trend and plunge of a lineation Place the back of GeoClino on the bedding plane (or else). Align the longer edge
onto the lineation, with the arrow in the upper right to the plunging direction. Read the data on display. On display, you see M showing MANUAL mode followed by number of measurement, then date and time in the upper line. In the lower line, you read the trend of the lineation, maximum dip of the plane and plunge of the lineation. Read as the trend of the lineation is N 30° W, maximum dip of the plane on which the lineation lies is 72°to W and the plunge of the lineation is 24°, for example. Cautions *
Place the longer edge of GeoClino parallel to the lineation holding the arrow to the plunging direction. If you want to measure the upward direction of the lineation, for instance the direction of fault movement, place GeoClino with the arrow to that direction. The plunge angle is shown with minus sign.
*
The dip of the overturned plane is shown as "180° - measurement angle". An overturned plane dipping 30° is shown as 150°.
Guidebook for Road Construction and Maintenance Management
8 - 15
8.4 Slope Monitoring 8.4.1 Crack Monitoring The displacement of a crack is recommended to be recorded in three different dimensions (X, Y and Z). Boards and sticks will help gather displacement data and estimate the deformation rate as shown in Figures 8.23. Displacement: X
Displacement: Z Crack
Displacement: Y
Crack
Crack
Crack
Displacement Sticks: 5-10 m interval
Displacement Board Displacement measurement
Z (+) Y
X Z (-)
Displacement Stick
(Source: Japan Highway Public Cooperation 1982, Slope Inspection Guide 1) Figure 8.23
Crack Displacement Measurement
8.4.2 Wire Extension Meter Wire extension meter is a kind of self-recording equipment and monitor the movement of soil or slopes.
Figure 8.24
8 - 16
Wire Extension Meter
Guidebook for Road Construction and Maintenance Management
8.5 Soil Investigations 8.5.1 Boring and Core Sampling Drilling/boring and sampling are described in the DPWH Design Guidelines, Criteria and Standard, Volume I chapter 4, Subsurface Investigation. Appropriate equipments and technical capacity are required for good core recovery. Displaced material by landslide Core feature: clayey detritus Color tone: brown (mostly by iron oxide)
Boundary of different colors means slip surface of landslide
Non- displaced material: Base Rock Core Feature: Rod-Shaped Color Tone: Original Color Figure 8.25
Figure 8.26
Sample Core Boring at Landslide Portion
Sample Core Boring at Soft Rock Slide
Guidebook for Road Construction and Maintenance Management
8 - 17
8.5.2 Sounding for Soil Strength Test 8.5.2.1
Standard Penetration Test
The standard penetration tests (SPT) shall be carried out to obtain the necessary data for planning and design in accordance with the DPWH Design Guidelines, Criteria and Standards Volume I. -
A test-drive for 300 mm penetration of a split tube sampler with a shoe.
-
N-value indicates the number of drives for 30cm penetration of split tube sampler.
Figure 8.28
Schematic Diagram of
Standard Penetration Test 8.5.2.2
Handle
Dual Mass Dynamic Cone
Sigle Mass or Dual Mass Hammer, 8 kg or 4.6 kg
Penetration Test
famous field testing apparatus to sound the soil
strength
in
Shallow
575 mm
Dynamic Cone Penetrometeris one of Upper Rod
Pavement
Applications.
Anvil with Quick-Connect Pin
In case the subgrade and/or roadbed are
Upper Attachment
firm and DCP is not able to penetrate a Dual Dynamic
Cone
Penetrometer
is
advisable. It can measure the shear strength
Drive Rod 16mm dia.
Variable (1000 mm)
Mass
of soil with a CBR between 0.5 and 100.
Vertical Scale
Note: Dynamic Cone Penetrometer and Dual Mass Dynamic Cone Penetrometer conform
Tip (Reusable Hardend Point or Disposable Cone)
Foot
to ASTM D6951 and ASTM D6951 3,
Figure 8.29
respectively.
Penetrometer (Dual Mass Type)
8 - 18
Dynamic Cone
Guidebook for Road Construction and Maintenance Management
Dynamic Cone Penetrometer requires only one operator to do a test basically.
Figure 8.30 8.5.2.3
Operation of DCP
Simplified Dynamic Cone Penetration Test
Simplified Dynamic Cone Penetration (SDCP) is a small type of dynamic cone penetrometer, developed in Japan, Japan Geotechnical Society Standard (JGS) 1433-1955, for slope soil investigation
Advantage
of
Simplified
Dynamic
Cone
Penetration is light than ASTM Dynamic Cone Penetration, so that it's easy to carry on to the slopes. Five (5) kg hammer is dropped from a height of 50cm freely, and dropping numbers to penetrate 10 cm depth into the ground is recorded as Nd value (nos./10 cm). For convenience and effective use of the Dynamic Cone Penetration (DCP) test equipment, a rubber stopper that can be fixed at the upper end of the rod that can help maintain constant height of drop should be provided.
Figure 8.31 Simplified Dynamic Cone Penetrometer
Procedure (1) Attach the cone to the bottom tip of the rod, attach guide rod and hammer on the top of the rod. (2) Set cone and rod perpendicularly on the sounding point. (3) Confirm penetration depth by the self weight of the hammer (49 N or 5kgf) (4) Record Nd-value: required numbers of 50 cm height free dropping to penetrate 10 cm into the ground, The frequency of the dropping is made about once for three seconds. (5) If penetration depth is less than 2 cm by 10 times dropping, the test should be terminated. (6) Friction cut (drill by auger/catch, 2 pieces shovel, or rotation rod of more than 10 times) before dropping the weight. Each 10 cm depth is recommended (especially for soft clay, sands under ground water level).
Guidebook for Road Construction and Maintenance Management
8 - 19
Recording (1) ‘Intrusive depth’ and hammering times for every 10cm depth shall be recorded. Nd-value are automatically calculated by the spreadsheet. (2) In case of self weight penetration, penetration depth and ‘dropping times = 0’ are inputted. Then Nd –value = 0 Friction Cut The rod skin friction affects DCP
0
Nd-values, it is especially remarkable for 1
soft clay/or saturated sands. Therefore, friction cut is required. Method of friction
Depth (m)
2
cut is as follows:
3
-
4
Dig up hole to the examination depth so that the rod should not
5
touch the soil by hand auger. -
6
Rotate rod ten times or more before the hammer dropping.
7 0.00
0.20
0.40
0.60
0.80
1.00
Coefficient of friction loss
-
Pour
oil/dope
into
the
surroundings of the rod in the test Figure 8.32
Friction Loss on
Simplified Dynamic Cone Penetrometer Test
hole before the hammer dropping. The Figure on the left shows an example of coefficient of friction loss on Nd-value for common soils.
Coefficient of friction loss = Nd-value with friction cut/ Nd-value without friction cut Relation of Nd-value and N-value are shown in Table 8.X. Table 8.4
Estimation of N-value from Nd-value of SDCP
Nd: Nd-value (Value by dynamic cone penetration test)
Gravel
Sand
Fine-grained Soil (Clay/Silt) or Unknown
more than 4
N＝0.7+0.34Nd
N＝1.1+0.30Nd
N＝1.7+0.34Nd
4 or less
N＝0.50Nd N＝0.66Nd N＝0.75Nd N= N-value by standard penetration test Nd= Nd-value by dynamic cone penetration test (Source: Okada Katuya et. al 1992, Soil and Foundation, Japanese Geotechnical Bulletin)
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Guidebook for Road Construction and Maintenance Management
Sample Graph
Figure 8.33
Sample Output/Simplified Dynamic Cone Penetrometer
8.6 Ground Water Survey and Monitoring 8.6.1 Ground Water Logging This measurement equipment is to be installed for monitoring the water table and obtaining necessary data for slope stability analysis. Pure water has high electric resistance while salt water has low electric resistance. The logging detects ground water flow in salted borehole water by dilution phenomena. 1.
The electric resistance of groundwater in the borehole should be measured at 0.5m intervals as initial value.
Guidebook for Road Construction and Maintenance Management
8 - 21
2.
Salt should be put into the borehole and stirred to provide approximately 1% concentration of electrolyte.
3.
After 5, 10, 30, 60, 120, 180min, the electric resistance of groundwater in the borehole should be measured at 0.5 meter depth each. Figure 8.34
Schematic Diagram
of Groundwater Logging If groundwater fluid beds exist, salt water should be replaced with pure water between the depths of groundwater fluid bed, so the electric resistance of groundwater will be increased. A sample graph of groundwater logging is shown in Figure 8.35. Electric resistance increase as the time passes at some depths of water table.
Figure 8.35
Sample Graph of
Groundwater Logging Table 8.5
Classification Obvious groundwater flow bed Semi-obvious groundwater flow bed Potential water flow bed
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Criteria for Groundwater Logging
Increase of Electric Specific Resistance (Ω-cm) 30 60 120 min min min More than Dilution to 103 initial value More than More than More than 2 x 102 5 x 102 103 More than More than More than 102 2 x 102 3 x 102 (Source: Japan Landslide Association)
Geological possibility of slip surface Possible Possible Possible
Guidebook for Road Construction and Maintenance Management
8.6.2 Hand Held Water Quality Sensor Usually water quality tests on groundwater is carried out together with water logging. Hand-Held Water Quality Sensor is portable and a useful apparatus to conduct with water logging. Table 8.6
Objected Water Properties
Item
Indication range
Accuracy (Main unit)
Potential Hydrogen (PH) or Oxidation-reduction potential (ORP)
- 14.00
± 0.05 pH
-2000 -2000mV
± 5mV
- 0.00 mg/L, 0 - 200%
-
0.00 - 20.00 S/cm*
± 1%
Dissolved oxygen (DO) Electronic conductivity (COND) Salinity (SALT) Total dissolved solid (TDS） Temperature (TEMP) Turbidity (TURB）
- 4.00% - 40.00 (sea water salt) 0.0 - 100.0 g/L -5.00 - 55.00 - 800.0 NTU 0.0 - 800.0 mg/L
± 0.1% ± 2g/L Degree ± 3%
1) Connect reading unit 2) Push start button
3) pH value appears
and sensor
4) Push channel buttun 5) DO, COND, SALT, TDS, TEMP, and TURB values appear
Guidebook for Road Construction and Maintenance Management
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8.7 Strain Gauge with PVC Pipe 8.7.1 Summary of Pipe Strain Gauge The strain gauge PVC pipe is installed to detect the depth of slip surface and monitor its movement. When the pipe (installed in a borehole) is bent by the movement of a landslide, one side o is compressed and the other side is extended. Strain gauges with PVC Pipes are measuring instruments which can judge a slip surface and determine the degree of displacement by measurement of small changes in electric resistance value caused by the bending of PVC pipes. Generally, strain gauges are put on PVC pipes at 1 meter intervals.
Figure 8.36
Pipe Strain Gauge
8.7.2 Checklist for Installation of Pipe Strain Gauge *
Place marked side of PVC pipes (a side of strain gauges are attached) where the direction of landslide moving is expected.
*
Be careful not to cut lead wires. Do not grasp lead wires alone, grasp PVC pipes.
8.7.3 Strain Gauges Monitoring Sample graph of strain gauges monitoring is shown in Figure 8.37. In this graph, the value of strain increases at the depth of slip surface. If a landslide moves, the value of strain will be accumulated. Data not accumulated (only one time movement) is just accidental.
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Guidebook for Road Construction and Maintenance Management
柱 状 図 Drilling Log地
深
Symbo 記 l
（ｍ）
号
Depth 度
2000μ strain
Graph of Strain Gauges
パイ プ 式 歪 計変 動図
ＢＶ－１
２０００μｓｔｒａｉｎ
質
5m
5
10m
１０ｍ
10m 10
15m 15
15
15
15
15
15
15
15
15
15 １０ｍ
Cumu lative 深度別歪量 move ment
（μ ） strain
10m
6000 4000 2000 0
降
Daily 水 Rainf all量 (mm)
100
50
（ｍｍ）
Day日 月 Month 年
10
20 4
30
10
20
30
10
5
B
20 7
30
10
20
30
10
8
20 9
30
10
20
30
10
10
20
30
11
10
20 12
30
10
20
30
1) 2)
10
20 3
Value of accumulation (μ/month) More than 5,000 More than 1,000
Sample Pipe Strain Gauge Monitoring Criteria for Evaluation of Data of Strain Gauges
Variability Characteristics accumulatio
Very High High
of slip
Status of moving
surface
n Accumulative1) Accumulative
Overall judgments
possibility of existence
Tendency of
Possible Possible
Classification of
Activity and Type of
slip surface
landslide
Determined Semi-
More than 100
Low
Intermissive/ Destabilizing/
More than 100 (Short term)
Debris Landslide Slowly moving creep Impossible to conclude
Possible
Potential
Destabilizing
Need to continue Slip surface is not existent.
None
2)
/regressive
Accumulative: The amount of the strain increases in the time series. Regressive: The amount of the strain decrease in the time series.
Guidebook for Road Construction and Maintenance Management
existence of slip surface. observation.
Intermissive/ None
Active Rock Landslide-
determined
Regressive D
20 2
2005
Accumulative/ C
10
1
パイプ歪計変動図
Table 8.7
A
10
Graph of Strain Gauges
Figure 8.37
of Movement
30
2004
Year
Classification
20 6
Abnormal
Caused by other factors, except landslide.
Source: Strain Gauge Criteria in Japan
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Borehole BV-1 (Road Shoulder)
GL-3m Semi-deter mined slip surface GL-6m Semidetermined slip surface
Borehole BV-2
GL-2m Determined slip surface GL-12m Semi-determined slip surface
Figure 8.38
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Monitoring of Pipe Strain Gauge (Sample Output)
Guidebook for Road Construction and Maintenance Management
GL-2m Semi-determined slip surface
GL-6m Potential slip surface
GL-2m Determined slip surface GL-12 m Semi-determined slip surface
Figure 8.40
Monitoring of Pipe Strain Gauge (Sample Profile)
8.7.4 Digital Strain Meter Digital Strain Meter is
necessary
Name of Parts
to
determine Strain Gauge.
Guidebook for Road Construction and Maintenance Management
8 - 27
Usage The strain meter is turned on by pressing "POWER" key. To turn off the strain meter, press "POWER" key again. Every individual depth of pipe strain gauges
Normal Mode
are measured by "Normal Mode" is selected. Press F2/CH key to select channel setting mode.(Channel number display is highlighted.) Normal mode and multi-channel mode is selected alternately at every time SHIFT key is pressed. However, mode changeover is not settled by this operation only. A.
Mode is settled by pressing ENT key.
B.
Mode changeover is quitted and former mode remains effective by pressing DEL key.
Contrast of main Liquid Crystal Display (LCD) is adjusted by ▲ and ▼ keys in monitoring mode. ▲ key: Contrast is increased. ▼ key: Contrast is decreased Back light of main Liquid Crystal Display (LCD) is turned on by pressing F1/LIGHT key in monitoring mode. To turn off the back light, press F1/LIGHT key again. When back light is turned on, power consumption increases about twice as that of without back light. Back light is automatically turned off by approximately 30 seconds while TC-31K is powered by battery. This is an operation to specify the sensor mode of connected sensor. Press "1/SENSOR" key to enter the sensor mode setting. (Sensor mode number display is highlighted.) Sensor Mode A.
Input sensor mode number "15" for Half Bridge Type Strain monitoring.
B.
Input sensor mode number using ▲ and ▼ keys. ▲ key: Mode number is increased.
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Guidebook for Road Construction and Maintenance Management
▼ key: Mode number is decreased C.
Sensor mode is settled and setting mode is finished by pressing ENT key.
D.
Former sensor mode remains effective and setting mode is quitted by pressing DEL key.
Refer to Figure 8.41 and 8.42 for connection Moving direction
of pipe strain gauges namely half bridge type (2
Lead Wire
gauges). Water Proof Coverage
Strain Gauge PVC Pipe Direction Mark
Figure 8.42
Connection with Half Bridge
Figure 8.41
Type
Strain Gauges with PVC Pipe Name of Parts
Connection of A and C are changed for every depth and values are recorded as Normal and Reverse. The values measured shall be recorded into the recording sheets for Pipe Strain Gauge Analysis.
Guidebook for Road Construction and Maintenance Management
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