Method Statement PDA-2011

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd

Table of Contents

Part 1 : Introduction

Part 2 : The Company

Part 3 : High Strain Dynamic Pile Load Test Test Using Pile Driving Analyser 

DLT

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd 1.0 Introduction

1.1 Purpose The purpose for this document is to define the methods for conducting Acceptance Tests on installed foundation piles using Stress-wave methods.

1.2 Scope The test methods described in this document includes: High Strain Dynamic Pile Load Test using Pile Driving Analyser  DLT •

These test procedures have been employed extensively on piles including: Driven Piles Jack-in Piles Micropiles Bored Piles Caisson Piles • • • • •

1.3 Plant and Machinery Specifications and description of the hardware to be used for the tests have been appended to this document. Relevant Calibration Certificates for sensors will be provided at time of test when required. .

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Part 2 2.0 The Company ENGINEERING LABORATORY SERVICES is an independent testing company that provides specialized services for testing of piles jointly with TEKTON BEACON Sdn Bhd, Malaysia. The methods of testing include one or both of capacity and qualitative measurements. Types of test services include: Dynamic load testing Pile integrity testing Cross Hole Sonic Logging of Piles Pile Driving Monitoring Static Load Test with Instrumentation Other services provided by the company include: Geotechnical Instrumentation Structural Instrumentation Soil Investigation Geophysical Survey Laboratory Testing Foundation Design and Installation Manufacturing of Precast Concrete Piles

ENGINEERING LABORATORY SERVICES - TEKTON BEACON owns and operates the state-of-theart pile testing system employing Stress-wave Analysis techniques. Such systems were developed by engineering institutions and have been extensively used, worldwide for more than 35 years. The company maintains a close working relationship with the developers and manufacturers. Such associations offer direct access to a wide field of expertise and experience in the area of Foundation Quality Assurance. The company consists of personnel with many years of experience not only in the area of pile testing but also pile design and installation. This places the company in a very good position to provide Pile Load Testing Services.

TEKTON BEACON is a SIRIM/UKAS certified ISO 9001 company. The mode of operation and conduct of its staff is governed by procedures that have been implemented to enable continuous improvement in the level of service to the customer.

TEKTON BEACON is a registered contractor (G2) with the Construction Industry Development Board of Malaysia.

TEKTON BEACON is a regional operator with work experiences in the Indonesia, Philippines, Sri Lanka and Taiwan.

ENGINEERING & LABORATORY SERVICES is the leading service provider for Foundation Engineering, Soil Investigation, Laboratory Testing and Precast Concrete Products and Pile Manufacturing in Sri Lanka and the Maldives. It is and ISO 9001: 2008 certified company.

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Part 3 Dynamic Pile Load Test using Pile Driving Analyser  Analyser  3.1 Definition High Strain Dynamic Pile Testing is basically a procedure to determine the static load capacity based on the effort required to drive the pile. Dynamic measurements of force and velocity (acceleration) at the upper end of the pile during pile driving, followed by signal matching procedure, is the most common method for dynamic determination of pile capacity.

3.2 Reference The procedure have been accepted and prescribed in several National Engineering Standards BS 8004: 1986, Clause 7.5.2.2 ICE Specification for Piling 1996, Clause 11.2 ASTM D – 4945 – 96 AS2159 (7), Standards Australia 1995 JGJ 106-97 (21), China, Technical Code for Building Foundation DGGT – 1997 (Germany) rd Ontario Bridge Design Code 3 Edition, Canada • • • • • • •

3.3 Plant and Machinery Field equipment consists of 4 components A set of strain transducers mounted near the top of the pile A set of accelerometers mounted to the top of the pile A Pile Driving Analyzer (PDA) A hammer to cause sufficient impact force on the top of the pile to allow measurement mobilized pile resistance. The hammer may be a drop hammer for testing of bored piles or the piling hammer used for pile driving in the case of driven precast piles • • • •

3.4 Basic Process

The pile driving analyzer monitors and registers the output from the strain transducers and accelerometers as the pile is driven or impacted during a test. The strain data, combined with the modulus of elasticity and cross sectional area of the pile gives the axial force in the pile The acceleration data integrated with time produces the particle velocity of the waves traveling through the pile The acceleration data, double integrated with time produces the pile set per blow. •

•

•

The force-velocity over time data from each impact constitutes a test record that enables the pile resistance mobilized by the particular impact to be determined. The PDA computes the mobilized pile resistance using the on-board software, named the CASE Method Analysis. The computation is practically real-time, that is the out put is displayed almost instantaneously after each impact from the hammer.  A second analysis using the more rigorous CAPWAP (CASE Pile Wave Analysis Program) software will be conducted on the selected set of force-velocity record to compute the Total Load Capacity. This analysis is comparatively more time consuming that involves a signal matching pro cedure and is therefore carried out as post-field work. The reported mobilized pile resistance will be that determined using the CAPWAP Analysis.

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Part 3 Dynamic Pile Load Test using Pile Driving Analyser  Analyser  3.5 Fieldwork 3.5.1 Pile head preparation Bored Piles The top of the pile is to be provided with a steel sleeve for confinement /restraint against bursting of  the concrete during impact from the hammer. The steel sleeve can either be installed during concreting of the pile or it can be a build-up section of the pile to be constructed over the top of the installed pile after selection of the pile to be tested. The concrete at the top of the pile is to be finished level and be of comparable strength with the pile proper to receive the impact from the drop hammer. The thickness of the mild steel casing can be in the range of 8mm to 12mm. Driven Piles The pile head for driven piles do not usually require special preparations. The impact will be carried out with the hammer used for the driving operations striking the end plate that comes with the piles. In cases where the pile need to be cut, the pile head have to be cut squarely using a ‘diamond blade cutter’ and the striking surface be provided with a layer of epoxy mortar.

3.5.2 Attachment of sensors to the pile head Two pairs of strain transducers and accelerometers are to be attached to the sides of the pile top at approximately diametrically opposing positions. Where possible, the sensors are to be attached at 1.5 times or more the diameter of the pile below the top of the pile. The sensors are attached to the concrete of the pile using mechanical anchors installed into 6mm nominal diameter holes drilled about 40mm into the concrete. The holes are drilled using a portable electric drill.

3.5.3 Initialising Pile Driving analyzer   After the sensors have been installed onto the pile, the sen sors are connected to the Pile Dr iving  Analyser (PDA) using signal cables. A system check is then cond ucted and the relevant details of the pile are keyed into the PDA. The usual data entered into the PDA include: Project name Pile identification Length of pile below sensors Length of pile below ground surface Cross Sectional area of pile Specific weight of concrete of pile Speed of stress wave through the concrete • • • • • • •

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Dynamic Load Test on Driven Piles Set up

Pile Driving Hammer 

PDA

Pile to be tested

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Dynamic Load Test on Bored Piles Set up

Hammer  Hammer  Guide

Hammer  Guide Support Crane

Drop Height

Pile to be tested

Sensors to PDA

Note Configuration of the Guide Assembly may change according to the size of the hammer used

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Dynamic Load Test on Bored Piles Preparation of pile head Method 1 - Sensors installed below casing at pile top

Hammer 

Drop Height Steel casing for building up of pile

Top of sound concrete from initial pour 

~ 2000 mm or  1.5Xdiameter 

Force transducer   Accelerometer  PDA

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Dynamic Load Test on Bored Piles Preparation of pile head Method 2 – Sensors installed at window of steel casing at pile top

Drop Hammer 

Drop Height

Steel casing for building up of pile Top of sound concrete from initial pour 

~ 1.5X Diameter 

Force transducer   Accelerometer 

PDA

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Setup for Dynamic Load Test on Micro-pile

Hammer  ram Hammer Guide

 API pipe of micro-pile of  micro-pile Hammer drop: 1~2.5m

~1.0

Level for installation of  sensors

GL

Shaft of micro-pile

Lp

Le

- dimensions to be adjusted according to site constraints

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Setup for Dynamic Load Test on Micro-pile Pile head preparation and attachment of sensors

Strain transducers

 Accelerometers

 API Pipe

Outer casing

Pile head to be cut level

Strain transducers and accelerometers to be installed diametrically where possible

Top of outer casing and grout body

GL

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Part 3 Dynamic Pile Load Test using Pile Driving Analyser  Analyser  3.5 Fieldwork 3.5.4 Conducting impact test and logging test data When the setup is ready, a test impact will be carried out to check the system and effectiveness of the selected parameters. Appropriate adjustments to the hammer such as height of drop, positioning and cushioning will be carried out where necessary. Similarly, fine adjustment of the sensors may be carried out if necessary. Further impacts for the Acceptance Test on the pile are then carried out. The test will be terminated upon successful demonstration that the mobilized pile resistance equals or exceeds the required test load. The computation is carried out by a software employing the CASE Method for Dynamic Analysis. It is based on an analysis of dynamic forces and accelerations (velocity) measured while the pile is driven or impacted. Useful output information that can be displayed for each impact includes: Mobilized static load capacity Pile integrity Compression stress at pile head during impact Energy transfer from hammer during impact • • • •

If the output from the series of impacts indicates that the required resistance has not been mobilized, a check will be carried out to identify the causes. If it is determined insufficient energy have imparted to the pile, the drop height for the hammer will be increased to enable a higher energy transfer to the pile. If the output from several impacts even after increasing the drop height indicates that mobilized pile resistance is insufficient, the test will be terminated and the data is to be checked to establish the cause for the low pile resistance.  A check on the integrity of the pile will be conducted for every pile. This is carried o ut both by noting the pile damage analysis output from the software as well as studying the trend of the force-velocity wave trace.  A standard pile set meas urement may be taken during the dynamic load test on driven piles. The data for each impact will be stored on the hard-disk of the PDA.

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Part 3 Dynamic Pile Load Test using Pile Driving Analyser  Analyser 

3.6 Determination of drop height for hammer for dynamic load test 3.6.1 Bored Piles The height of drop will be dictated by the energy required to mobilize the pile resistances and limited by the stresses developed in the pile shaft. The determination for the height of drop is presented on the following pages.  A lower drop height will be employed at the star t of the test. The d rop will be increased progressively until sufficient energy transfer is achieved for measurement of the pile load capacity. A drop height higher than the calculated values may be necessary if the efficiency of the drop hammer is lower than assumed.

3.6.2 Driven Piles The height of drop will follow that used for the pile driving operations, if using the same hammer for the dynamic load test. If a different hammer weight from the pile driving operation is to be used, the height of drop for the hammer would then be computed using the same potential energy as employed. In cases where ‘soil set-up’ causes the shaft friction to increase by large amounts, it will be necessary to use a higher drop height for the hammer ram to cause the necessary mobilization of the pile resistance.

Limiting stresses from hammer impacts The test operation will be governed by the monitoring max stresses developed in the pile shaft: Example: Max. allowable compressive stress = 0.85 f’cu = 38 N/mm2, assuming f’cu = 45 N/mm2. Source: Driving stresses in Piles, by Garland Likins, Pile Dynamic Incorporated, USA

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Part 3 Dynamic Pile Load Test using Pile Driving Analyser  Analyser  3.6.3 Determination of drop height for drop hammer for dynamic load test The approach to be taken is to determine the range of drop height deemed suited to deliver an energy transfer to the pile head to mobilize the pile sufficiently for measurement of its load capacity using the Pile Driving Analyser. Simplified Energy Concept Test Load = TL Weight of hammer to be used = W Drop height to be employed = H Required Energy Transfer on to pilehead

=

Efficiency Factor

X

Potential Energy of Drop Hammer 

Experience from previous projects shows that an efficiency factor ranging from 10% to 40% can be achieved. Required Energy Transfer

=

Mobilised X Pile Resistance

Mobilised Pile movement

The pile resistance can generally be mobilized with a pile movement of 2.5mm or more. For determination of Hammer Drop Height, a mobilized pile movement of 3.5mm will be used. Therefore, For efficiency factor of 10%, TL X 0.0035 = 0.10 X W X H H = (0.035 TL) / W For an efficiency factor of 40%, TL X 0.0035 = 0.4 X W X H H = (0.009 TL) / W Example Guideline for Drop Height of Hammer for Dynamic Load Test Pile Size Test Load Weight of  Drop Height, m Mm TL (t) Hammer (t) at 10% efficiency

Drop Height, m at 40% efficiency

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Part 3 Dynamic Pile Load Test using Pile Driving Analyser  Analyser  3.7.0 Hardcopy (field sheet) recording of events  A handwritten field record of the testing event will be prepared for each test day. The infor mation provided on the field sheet include: Project name Pile identification Length of pile below sensors Length of pile below ground surface Cross Sectional area of pile Material strength Design Working Load Required Test Load Date of pile installation Date of pile load test Type of Hammer  Height of Hammer Drop Specific weight of concrete of pile Speed of stress wave through the concrete Values of key output; RMX, RSU, FMX, CSX, EMX, BTA for a selected blow/impact data Measured set, if applicable • • • • • • • • • • • • • • • •

The field sheet is to be signed off by the a representative each from the contractor, engineer (and client, if applicable) to signify presence during the test.

Typical PDA Output Quantities RMX RSU RA2 FMX CSX CSB TSX EMX BTA LTD

Maximum Case – Goble resistance (using JC) Case – Goble resistance using damping corrected for early unloading Case – Goble resistance independent of damping JC Maximum measured compression uniform force at the transducer location Compression stress maximum Compression stress at bottom of pile Maximum tension stress Maximum energy transmitted past the transducers Pile integrity factor for pile damage analysis Length to damage below sensors

Typical PDA Input Quantities LP Pile length penetration LE Pile length below gauges to the pile bottom  AR Cross sectional area of the pile EM Elastic modulus of the pile SP Specific weight density of the pile material WS Speed of stress wave in the pile

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd Part 3 Dynamic Pile Load Test using Pile Driving Analyser  Analyser  3.8 Computation of Pile resistance The collected wave trace from the fieldwork will then be analysed with a specialized software named CAPWAP (Case Pile Wave Analysis Program) to compute the mobilized pile resistance. CAPWAP combines measured force and velocity data with wave equation analysis to obtain the soil resistance effects acting on the pile.  A representative blow shall be selected f rom the pile top forc e and velocity signals recorded in the field. CAPWAP analysis involves applying the measured pile top force/velocity time record as a boundary condition to a wave equation model of the pile comprising of continuous segments. The soil model is continuously adjusted in an iterative procedure until the computed pile top force time record is in close agreement to the measured pile top force time record. When good agreement is achieved between measured and computed pile top data the soil resistance parameters are assumed to provide the best representative model of the actual soil. Hence the computed load capacity obtained through the CAPWAP analysis provides a good estimate of the actual capacity contributed both by the shaft resistance and end bearing.

The output from the computation will consist of: The total mobilized static pile resistance for the selected blow/impact The mobilized shaft resistance The mobilized toe resistance The distribution of the shaft resistance The simulated load settlement curve

• • • • •

3.9 Preparation and submission of Report The results for each day’s test will be compiled into one report to be submitted within 10 days of the fieldwork. Each report will be serialized and contain the following segments: Table of content Summary of test results Brief description of test procedure Key information on the project Summary table of key data and outputs Work sheets for CAPWAP Analysis Wave trace of collected data for selected blow/impact including output for CASE Method Analysis Field sheet with information as recorded on site Calibration certificates for sensors used.

• • • • • • • • •

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd

3.10 Sample

of Field Sheet for Dynamic Load Test Engineering & Labor atory Services (Pvt) Ltd FIELD SHEET FOR DYNAMIC PILE TESTING

Client Name

:

Date :

Project Name :

Test Personnel : Transducers:

Mahinda F1:

PDA Eqpt Set No : F2:

Accelerometer :

A1:

A2:

Pile ID Pile Details Pile Type Pile Size Temporary Casing (m) Permanent Casing (m) Section Section Area Area (cm ) Material Strength (MPa) Total Pile Length (m) Length Below Gauges (m) Penetration Length (m) Pile Make-up (m) [top-btm] Working load (tonne) Required Test Load (tonne) Hammer Details Hammer Type Ram Weight (tonne) Drop Height (m) PDA Field Results RMX (tonne) RSU (tonne) FMX (tonne) CSX CSX (t/c (t/cm m ) EMX (t-m) Integrity Supplemental Data Wave Speed (m/s) Density Density (t/m (t/m ) Measured Set (mm) Date Driven/ Casting Testing verification by Company :

Company :

Name

Name

:

Signature :

Revision No.:0

:

Signature :

Issue No. :1

Issued Date : 09 Sept 2000

Engineering & Laboratory Services (Pvt) Ltd Tekton Beacon Sdn Bhd