Pile Testing and Monitoring at SGES

An efficient pile design always comes from a deep understanding of the engineering properties in the site, pile, and any other complex changes that occur during the installation. This is precisely where SGES steps in as a supreme pile monitoring and testing service provider. To date, we have helped many companies test the integrity and reliability of the deep foundation. Below is detailed information on the comprehensive capabilities of pile testing that have been the core competencies of SGES for years.

High Strain Dynamic Pile Testing (HSDT) (ASTM D 4945)

Offshore Pile Monitoring/ Dynamic Pile Testing (Over Water and Under Water Monitoring of Offshore piles)

Instrumenting offshore piles to monitor driving performance and pile/ soil response to measure the mobilized compressive capacity has been one of SGES’s core competencies. A pre-installation drivability study for various driving conditions (i.e., SRD’s- soil resistance to driving) will be performed (using GRLWEAP software) to choose the optimal hammer size necessary to drive the pile safely to the intended target penetrations.

The pile driving monitoring is carried out by instrumenting a pair of strain gage and accelerometers at a predetermined depth below the pile top. A high strain compressive stress wave is generated upon an impact on the pile top by the hammer. The stress wave travels down to the pile toe. It reflects gage location where the force and velocity signals as a function of time are measured by strain gauge, an accelerometer connected to the Pile Driving Analyzer (by PDI Inc. USA) for every blow. This process is continued until the pile reaches the required penetration.

The force and velocity signatures thus captured by the PDA are further analyzed using a signal matching software viz., "CAPWAP" to confirm the mobilized compressive capacity (together with resistance distribution along shaft and toe) and to arrive at dynamic soil constants.

SGES has accumulated rich experience by monitoring driven piles of over 100 offshore platforms in offshore India, South East Asia, and Middle East geographies. These projects include monitoring of over-water driving as well as under-water driving of skirt piles using specially fabricated waterproof sensors.

A team of qualified and experienced geotechnical engineers/technicians will be mobilized on every project. The experience gained over several offshore pile monitoring projects of various oil companies enables us to make good field measurements and engineering judgment/ interpretations required for pile acceptance.The same test method can also be used to monitor pre-cast driven piles for hammer/driving system performance, driving stresses, and soil resistance to driving for the construction of on-land projects.

High Strain Dynamic Pile Testing (HSDT) on Bored Cast In-situ Piles

It is a quick, non-destructive test to measure the mobilized compressive capacity and evaluate the bored pile's structural integrity. A high strain compressive stress wave is generated upon an impact on the pile top by a free fall guided drop-weight. The stress wave travels down to the pile toe and reflects the gauge location, where a strain gauge and accelerometer measure the force and velocity signals as a function of time.

A pretest desktop analysis is carried out to determine the weight, the height of fall, and driving assembly, i.e., pile cap and cushion thickness, based on the information provided, such as the ultimate load to be proved, pile geometry, and subsurface condition. Usually, a dead weight equal to 1-2% of the ultimate capacity to be proved is used as drop weight for testing the piles.

The test pile is instrumented with two pairs of strain gauge and accelerometer at about 1.5 times the pile diameter from the pile top. The pile top shall be neatly prepared with the leveled surface using concrete. The stick up length for mounting the sensors shall be made available by excavating around the pile or growing the pile above the ground level. The impacts are given on the center of the pile top by dropping the predetermined dead weight from several heights so long as the stresses are within limits and the required compressive capacity is measured by Pile Driving Analyzer (by PDI Inc. USA).

An experienced geotechnical engineer with extensive knowledge of operating PDA and wave theory can decide when to stop the testing and raise concerns about defects/damage.

The force and velocity signatures thus captured by the PDA are further analyzed using a signal matching software viz., "CAPWAP" to confirm the mobilized compressive capacity (together with resistance distribution along shaft and toe) and to arrive at dynamic soil constants. CAPWAP will also provide an equivalent static load-deformation curve.

This test method is advantageous over the conventional static load test method by reducing testing time and providing additional information such as pile integrity. SGES, since its inception, has been involved in the quality control of deep foundations on various projects by testing the piles (of sizes varying from 3 inches to 1.5m diameter) with dynamic methods and providing solutions to anomalies if detected.

Low Strain Dynamic Pile Testing/ Pile Integrity Testing (PIT) –ASTM D5882

It is a quick, non-destructive test to check the integrity of the pile shaft. A low strain compressive stress wave is generated by an impact using a hand-held hammer (either regular or instrumented) of weights ranging from 0.5 to 4.0 kg, depending on the geometry and length of the pile.

The stress wave thus generated is recorded as force and velocity as a function of time using the Pile Integrity Tester (by PDI Inc. USA). The recorded force and velocity curves are interpreted for pile shaft integrity and length.

An experienced geotechnical engineer with extensive knowledge of wave theory can interpret the data and raise the concern for pile defect/damage, if any. SGES will mobilize an experienced team of engineers/technicians on every project.

The data recorded can be further analyzed using PIT-W software (by PDI Inc. USA) by performing necessary filter and data adjustments for better toe interpretation. Profile analysis shall be performed to arrive at the pile profile.

Usually, 100% of the piles will be tested for integrity, providing quality control for the installed pile.

Cross Hole Sonic Logging

Evaluation of concrete quality in deep foundations by the Crosshole Sonic Logging method (CSL)

• Allows four probes of trans-receivers (six profiles) to be pulled at once for ease and efficiency of data collection
• Assesses concrete quality and consistency of drilled shafts and other cast-in-place concrete structures
• Performs real-time analysis on site, as well as data transfer with CHA-W reporting software for additional analysis
• Available in a 2-channel or a 4-channel system
• Offers PDI-TOMO, 3-D tomographic software for superior tomographic results of questionable areas.