A conventional static load test on a pile provides limited information as only applied load and displacement at pile top are observed. However, if such a static load test is complemented with instrumentation it provides much more information. Geo Dynamics provides instrumentation for vertical load tests by placing vibrating wire strain gauges at pre-selected levels on reinforcement cage. The same vertical load test in this case shall provide readings from strain gages at each location and it is then possible to evaluate unit friction from a set of complex calculations and expert interpretation at the given locations. Extensometers too are also installed at specified levels for measuring pile shaft movements. Geo Dynamics also have range of Load cells which can be used to directly measure the load applied to the pile. For lateral load tests and to monitor lateral ground movement, Geo Dynamics provides inclinometer services to plot the lateral movement of the ground or pile and also to determine the depth of fixity. Geo Dynamics has state of the art In-Place Inclinometers in additional to torpedo type inclinometer for continuous real time monitoring.
Geo Dynamics has successfully conducted instrumented load tests for Cochin Metro for a large 2m pile and for several other clients. Our work has been verified by international experts. We have been able to break the myth in India that instrumentation works only on paper. Currently, Geo Dynamics is well-equipped to provide instrumentation for bored piles for vertical and lateral load tests to accurately evaluate friction, end bearing, unit skin friction, elastic compression, lateral deflection etc.
Precautions
It is imperative that an instrumented load test is planned properly and well in advance with a proper choice of number and location of vibrating wire strain gauges. Interpretation of the tests require several calculations and need an expert with good understanding of pile soil interaction.
Code Compliance
There are no specific guidelines for fixing the amount and type of strain gages or extensometers. Thus it is imperative that there is agreement with the client to ensure adequate numbers to avoid redundancy of gages. The load test is conducted as per IS:2911 (Part:4)
Equivalent International Standards
Static load tests are standardized by ASTM D1143, Standard Test Methods for Deep Foundations Under Static Axial Compressive Load; ASTM D3689, Standard Test Methods for Deep Foundations Under Static Axial Tensile Load; and ASTM D3966, Standard Test Methods for Deep Foundations Under Lateral Load.
Results
The interpretations are able to provide the following
- Capacity or nominal soil resistance
- Load Settlement profiles
- Load transfer behavior of pile along the length
- Deflected shape of the pile