Pile are required for buildings, bridges, towers, dams and other massive structures. A variety of pile types can be installed by different driving equipment in all types and even in layered soils makes establishing a safe but economical installation difficult.

Static Pile Load TestingDynamic Pile Load TestingStatnamic Pile Load Testing

More EconomicalLess Time ConsumingMore EfficientAlternative for Static Pile Load Test for Offshore pilesLess logistics involved Provide more information regarding a pile when compared to a static load test

Low Strain Dynamic TestingHigh Strain Dynamic Testing

Low Strain Pile Integrity Testing is a quick and cost effective method to evaluate the shaft integrity of concrete piles. The testing is able to provide information on:pile continuityconsistency of materiallocation of defectdegree of defectThe test method is performed with a hand held hammer, a sensitive accelerometer and the Pile Integrity Tester.

High strain dynamic testing consists of estimating soil resistance and its distribution from force and velocity measurements obtained near the top of a foundation impacted by a hammer or drop weight.

The impact produces a compressive wave that travels down the shaft of the foundation.

A pair of strain transducers obtains the signals necessary to compute force, while measurements from a pair of accelerometers are integrated to yield velocity.

These sensors are connected to a PDA that records, processes and displays data and results.

PART ONE: GENERAL

It involves attaching strain gauges and accelerometers to the pile near the pile head during drivingIt shall be performed on required number of indicator pilesDynamic Testing shall be performed on production piles as chosen by the engineer to monitor hammer and driving system performance

Specifications For High Strain Pile Load Testing:

PART TWO - Material Impact Force ApplicationForce or Strain TransducerAcceleration or Displacement Transducer Signal Transmission CablesPDA (Model Pak, PAX or PAL) to record, display and analysis data

PART THREE EXECUTION: Its mandatory that both the accelerometer and strain gage are fixed parallel to the pile axis at a predetermined distance from the pile top. When two sets of gages are used, they shall be diametrically opposite

High Strain Pile Load TestingPreparation: The transducers strain gauges and accelerometers are fixed on the pile after performing the initial calibrations checks on them. These are fixed either by bolting or welding. Setup the apparatus required for data recording, reducing and displaying data.

Calibrations of the Strain gauges and Accelerometers & Fixing of gauges.

Preconstruction Wave Equation AnalysesDynamic Testing Consultant shall propose driving system to install the pile to the required capacity and desired penetration depth within the allowable driving stresses, with prior information got by Contractor.In case of Bored piles, design weight, drop height and cushion of the hammer apparatus shall be proposed.Proposed Driving System by the engineer shall be based upon the wave equation analysis.A new pile driving system shall be proposed by the contractor if the pile installation stresses calculated exceed the maximum values specified by the engineer.Indicator Pile Program: Indicator piles shall be driven based upon the preliminary driving resistance indicated by wave equation results.Based on the results, the engineer shall select number of indicator piles to be statically load tested.

Production Pile TestingDynamic Pile Testing shall be performed on piles during initial driving, restrike driving , initial and restrike driving.Engineer may request additional piles to be dynamically tested if hammer is modified or replaced or any other piling behaviour different from the normal installation procedure.PART THREE Reports:CAPWAP analyses of the dynamic pile testing data shall be performed on data obtained from the end of initial driving and beginning of restrike indicator pilesUpon completion of various testing phases, the Dynamic Testing Consultant shall prepare a formal report summarizing the dynamic testing results.

Advantages:For caissons and drilled shafts, it provides a less expensive alternative to static load testing. For driven piles, testing can be done during installation and/or re-strike very economically.Dynamic pile monitoring has the advantage of providing immediate results that the engineer can use, including estimates of capacity, driving stresses, and pile integrity. Low strain dynamic testing method is a quick, convenient way to check deep foundations for defects. Low strain dynamic testing can be used on concrete piles, drilled caissons, augered cast-in-place piles, concrete filled pipe piles, and timber piles of moderate slenderness. It is possible to check numerous piles on site during a single day.

Transducers PDA system:Compact, reliable, water resistant, combined acceleration/strain transducers, cables and connectors.Mounting jig to increase transducer life and for protectionJunction box for easy mounting and storage of transducer cablesSignal Conditioning PDAMaximum reliabilityFull digital signal processingBattery and AC poweredNo. of files digital signals only limited by hard disk capacityTest Box to test system functions.Software Environment PDAWindows based environmentEasy InstallationHigher quality signal processing

Proven worldwide application nowUses available or easy-to-make drop hammers and minimal pile preparationConfirms capacity, even at large loads Reduced testing time and large cost savings (cost 10 to 30 times less than static cost)PDA with CAPWAP evaluates capacity at low cost for driven piles, drilled shafts,& augercast piles PDA gives extra valuable information (integrity, stresses, hammer energy)PDA potentially saves time or pile length in favorable site conditionsImproves quality control by more pile tests

Site specific input factors, such as damping, rapid pore pressure cant be obtained by PDA testing.An experienced Geotechnical engineer or PDA operator is needed to go through the PDA analysis to avoid misinterpretation of the results obtained.

Normal Force Velocity v/s Double Impact CurveSometimes hammer components, cushions, helmet and pile may produce a Double Impact effect in the measured test records. This may be due to development of the hammer system impacting event and/or frequencies in the multi-degrees of freedom driving system. Though this feature has no effect on the quality of the data and doesnt require special attention in data analysis.

Dynamic Pile driving stresses, especially in tension, produce micro-cracks in concrete piles. Fig A shows test records with normal characteristics. While Fig B contain the features indicating the development of tension cracks along the pile length. This is shown by an elongated wave reflection from pile toe at 2L/c time. The records can be evaluated in real-time driving to monitor pile structural integrity.

MSRDC 55 Flyover Scheme : Dynamic Pile Testing was extensively used for the above flyovers in Mumbai after conducting many co-relation studies between static & dynamic tests to prove the reliability of High Strain Dynamic Testing. This resulted in significant savings in time and early completion of many flyover projects thus helping the contractors and clients. Further the problem of space availability, which for flyovers in middle of the road was solved resulting in greater working space and more work efficiency for the contractors. Testing was conducted on piles ranging from 600mm to 1200mm piles and capacity ranging from 180 tons to 1375 tons.

Delhi Metro Project : Dynamic Pile Testing is being extensively used for Delhi Metro Project where it was used to ascertain capacity of many suspect piles. Numerous co-relation studies were conducted to evaluate the test method & acceptability of the test agency. The results were successful and more than 30 tests have been conducted till date. Testing was conducted on 1500mm piles with test loads upto 675 tons.

Baroda Ahmedabad Expressway Project : NHAI located 128 piles of 500mm that were abandoned by the previous contractor more than 10 years back. No technical data like pile depth or capacity was available. A combination of dynamic and pile integrity tests was used on the project site. Initially PIT conducted on the piles reported pile lengths about 20m. Borehole taken adjacent to two such typical piles confirmed the findings. Dynamic testing on the pile helped establish its design load. Static test was also conducted by the client on the pile dynamically tested for further confirmation. The static and dynamic test results matched well helping the client save lot of time and money, since most of the piles could be used in further construction at no additional cost.GCPTCL Jetty at Dahej : Dynamic Pile Testing was adopted at one of the longest jetty in Gujarat after co-relation with static testing on a land pile. Conventional testing on this jetty would have been extremely difficult, time consuming and expensive. Replacement of static testing by dynamic testing significantly helped in early completion of the project.

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