Design and Planning of Instrumentation Works
AECOM Singapore LIM Chi-Sharn Associate / Principal Engineer (Geotechnical)
[email protected]
09 May 2013
Outline •
Introduction and Objectives
•
Design of Instrumentation Instrumentation and Monitoring Systems Systems
•
–
Bored tunnelling
–
Mined tunnelling
–
Deep excavation
Planning of Instrumentation and Monitoring Systems Systems –
Risk Management
–
Information Management
–
–
•
Contingency Planning Ensuring Reliability (System Assurance)
Challenges 09 May 2013
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Tunnelling and Excavation causes
Ground Movements & Other Changes which are kept Within Acceptable Limits in order to Ensure Safety & Protectt Adjacent Structures Protec 09 May 2013
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What is Instrumentation & Monitoring?
Instrumentation is
Monitoring is
a Surveillance System
at Site 09 May 2013
4
2
Tunnelling and Excavation causes
Ground Movements & Other Changes which are kept Within Acceptable Limits in order to Ensure Safety & Protectt Adjacent Structures Protec 09 May 2013
Page 3
What is Instrumentation & Monitoring?
Instrumentation is
Monitoring is
a Surveillance System
at Site 09 May 2013
4
2
Objectives To Verify Design Assumptions Assumptio ns by Comparing Monitored responses against Predicted Values
To Ensure Safety by Limiting Magnitudes & Restricting Trends of Responses
To Minimize Damage of surrounding Structures & Buried Cables, Pipes etc.
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Construction Works Works as an Engineered System QUALITY ability to satisfy requirements
Serviceability use for purpose and for conditions
Safety acceptability of risks
Compatibility acceptability of impacts
Durability freedom from unanticipated degradation
(Bea, 1994, 2002) •
Equipment – reliable
•
Processes – clearly defined
•
People – clear roles and responsibilities 09 May 2013
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3
Benefits of Instrumentation & Monitoring (from Dunnicliff, 1993) •
Defines initial site conditions conditio ns such as groundwater, groundwater, background conditions (temperature, (temperature, noise, vibration, tides)
•
Proof testing (test piles)
•
Safety and Risk Management
•
Observational approach to design and design verification that is based on data
•
Construction control
•
Legal protection
•
Enhances public relations 09 May 2013
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What are Monitored? •
•
Ground Movement –
Settlement (& at Depths), Heave (& at Base)
–
Lateral Displacement Displacement (& along Depths)
Ground Water –
•
Structural Forces –
•
•
Water Table / Pore Water Pressure
Strut/Ground-Anchor Supports, Tunnel Lining
Structural Deformations –
Tilt & Crack Widths of Buildings/Structures
–
Utilities; Cables & Pipes
–
Profile & Shape of Tunnels
Vibration and Noise 09 May 2013
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TYPICAL INSTRUMENTATION 09 May 2013
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Ground Settlement Markers
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Settlement Plates
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Settlement at Depth (Magnetic Extensometer)
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Settlement at Depth (Hydraulic Hook )
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Settlement at Depth (Hook Sensor)
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Deep Leveling Datum
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Water Stand Pipe
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Water Stand Pipe & Piezometer
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Vibrating Wire Piezometer
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Piezometer
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Push-in Type Piezometer
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Building Settlement Markers
For Asphalt Surface
For Concrete Surface 09 May 2013
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Building Settlement Markers
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Tilt Meter
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EL Beam Sensor
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EL Beam Sensor As In-Place Inclinometer & for Settlement Profile
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Convergence Monitoring
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Convergence Monitoring
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Tape Extensometer
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Crack Meter
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Strut Load Measurement
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Brillouin optical time domain reflectometry (BOTDR)
Diagram courtesy of ntt.co.jp/news
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Distributed strain sensor – BOTDR Average strain over 1m every 20cm Range ~5-10km Resolution 30με (0.003%) Low cost sensors - optical fibre 5 - 25 minutes per measurement Can link or switch between fibres
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DESIGN 09 May 2013
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Design Aspects
•
Purpose of instrument –
•
Location of instrument –
•
What are the safe limits?
Frequency and duration –
•
Where is it to be installed?
Review levels –
•
What is to be monitored?
When and how often is it to be monitored?
Contingencies –
What should be done when the limits are exceeded, and who should do it?
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Design Verification – Tunnelling
•
•
•
Verification of parameters –
Water table
–
Volume loss
–
Ground relaxation
Comparing predictions with outcomes –
Ground movements
–
Groundwater changes
–
Convergence / radial displacement
Monitoring at areas of risk –
To manage residual design risk, construction risk
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Trough Measurements Help to Identify Types of Ground Movement
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Settlements at Surface Vs at Depth
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Monitoring Arrays (Tunnelling)
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Monitoring Arrays (Tunnelling)
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Monitoring Arrays (Tunnelling)
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Monitoring Arrays (Tunnelling)
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Monitoring Arrays (Tunnelling)
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Interpreted Monitoring Data
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Convergence Monitoring (Bored Tunnel)
•
•
For Both Tunnels, –
Min 1 for each drive
–
Min. 1 at each soil type encountered
For 1st tunnel, –
Min one at every 100m if clear space <
–
Min one at every 25m if clear space < 3m
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Convergence Monitoring (Cross Passages using SCL)
•
Every 2m from breakout
•
7m from breakout
•
Every 20m thereafter
m m m m 0 2 4 6
m 7
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m 0 2
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Monitoring Ground Water Level
•
•
Currently Not Monitored at Close Interval To Determine Correct Face Pressure with Reference to Ground Water Pressure for Both Slurry and EPBM
•
To limit Ground settlement
•
To avoid Ground heave, slurry spouts and foam spews
•
To validate the design of tunnel segment
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Examples
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Examples
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Examples
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Examples
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Role in Risk Management – Managing residual design risk and construction risk •
Tunnelling
Before tunnelling under buildings (esp. with mixed ground)
Start of tunnelling
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Cavities are Not Always Fully Grouted
Leca, E. & Domieux, L. (1990)
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Subsurface Monitoring – Rod extensometers @ Close Intervals?
Drawback – Risk of Slurry Path
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Monitoring for unplanned stoppages
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Design Verification – Excavation
•
•
•
Verification of parameters –
Water table
–
Soil properties
Comparing predictions with outcomes –
Ground movements
–
Groundwater changes
–
Retaining wall deflections
–
Strut forces
Monitoring at areas of design risk –
To manage residual design risk
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Monitoring Arrays - Excavations
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Monitoring Arrays - Excavations
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Examples
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Examples
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Examples
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Examples
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Examples
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Interpreted Monitoring Data •
Possible causes –
Observed soil profile different from design no F2 at the East Wall
–
Marine clay Cu and Eu lower than adopted at design
–
Back-Analysis of Unpredicted Sway of a Cut-And-Cover Deep Excavation in Singapore Marine Clay (Lim et. al. 2011. Proc of ICAGE) 09 May 2013
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Role in Risk Management – Managing residual design risk and construction risk •
Excavations 3D (??)
2D (ok)
The Impact of Geometry on Re-Entrant Corner Behaviour in Deep Excavation Retaining Walls: Two Case Studies from Stage 4 of the Circle Line. (Lim C.S. and Jee Y.Y., 2008, Proc. Of ICDE) 09 May 2013
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Ensuring Safety and Minimizing Impact – Adjacent Structures
•
•
Comparing predictions with outcomes / safety limits –
Ground movements
–
Groundwater changes
–
Building movements and strains
Comparing outcomes with legal limits / guidelines –
Noise
–
Vibration
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Structure Monitoring
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Structure Monitoring
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Structure Monitoring
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Effects of tunnelling on pile foundations (slide from Mair, 2009)
W
Base Load
W=F+B F
B
Volume Loss B
Shaft Friction F Volume Loss 09 May 2013
Tunnel volume loss causes base load B to reduce, pile settles and shaft friction F increases Page 77
Bored tunnelling below full scale pile trials in the Second Heinenoordtunnel site (Kaalberg et al, 2005) (slide from Mair,
2009)
distance from tunnel (m) -30
-20
-10
0
10
0
•
4
-10
) m m ( -20 s t n e m -30 l t t e s
) m ( l e v e l -6 f . e r w o -11 l e b h t -16 p e d
-1
pile settlement surface settlement piles
-40
tunnel
-50
-21 -30
-20
-10
0
•
•
10
Field trials : wooden and concrete piles above two 8.3m OD tunnels End-bearing piles , shaft friction very low Volume losses –
Zone B Zone A Zone C
30o
–
45o •
• • •
Piles in Zone A settle > ground surface Piles in Zone B settle ~ ground surface 09 May 2013 Page 78 Piles in Zone C settle < ground surface
1st tunnel : 1~2% 2nd tunnel : 0.75%
0.5D was considered to be safe distance between pile toe and tunnel
39
Structure Monitoring (Real Time)
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Structure Monitoring (Real Time)
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Design Role of the Qualified Person for Geotechnical Aspects of GBWs
(Building Control Regulations) 09 May 2013
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PLANNING (For the construction phase)
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Supervision Role of the Qualified Person for Geotechnical Aspects of GBWs (8th Schedule, Part II, Building Control Regulations) •
Tunnels
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Supervision Role of the Qualified Person for Geotechnical Aspects of GBWs (8th Schedule, Part II, Building Control Regulations) •
Deep excavations
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Construction Works as an Engineered System QUALITY ability to satisfy requirements
Serviceability use for purpose and for conditions
Safety acceptability of risks
Compatibility acceptability of impacts
Durability freedom from unanticipated degradation
(Bea, 1994, 2002) •
Equipment – reliable
•
Processes – clearly defined
•
People – clear roles and responsibilities 09 May 2013
Page 85
Monitoring Works as an Engineered System QUALITY ability to satisfy requirements
Serviceability use for purpose and for conditions
Safety acceptability of risks
Compatibility acceptability of impacts
Durability freedom from unanticipated degradation
(Bea, 1994, 2002) •
Equipment – reliable
•
Processes – clearly defined
•
People – clear roles and responsibilities 09 May 2013
Page 86
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Role in Risk Management
Safety & Design RISKS are Managed by
Setting Limits on Each Response &
Comparing Monitored Responses Against these Set Limits 09 May 2013
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Interpreting monitoring data – key information required
3 Activity against trend
2 Trend graphically
FORM IS FUNCTION
visible
1 X-axis annotated with dates
4 Key plan with instrumentation locations
5 Table readings against Review Levels 09 May 2013
Land Transportation Excellence Awards 2011
Best Innovation Partner Page 97
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Instrumentation & Monitoring Quality Plan (1 of 2)
•
Sufficient & Correct Instrumentation
•
Proper Installation & Establishment of Initial Readings
•
Monitoring Schedule Updated Regularly & Strictly Adhered To
•
Readings Taken by Competent Technicians
•
Proper Data Deduction & Verification
•
Daily Results into Summary Format
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Instrumentation & Monitoring Quality Plan (2 of 2) •
Daily Trend Watch
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Daily Check on Results Vs Review Levels
•
Weekly Reports with Tables, Trend Plots
•
Regular Meetings among Key Personnel
•
Full Participation of QP(S) & PE
•
Increased Monitoring at High Risk Area
•
Increased Monitoring at High Activity Area
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Prompt Replacement of Damaged Instruments
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Calibration of Tools as per Schedule
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Manual checks of automated real-time monitoring 09 May 2013
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