Deep Foundation Load Capacity Assessment with Static Load Testing
Static Load Tests can be performed to validate foundation design assumptions regarding the axial compression or axial tension resistance provided by a deep foundation element, or its deflected shape under a lateral load. GRL performs both highly instrumented static load tests (SLT) to meet the need of project design tests as well as basic load tests, for construction quality assurance. Depending on the project requirements, loading condition, and deep foundation type, GRL can attach or embed vibrating wire strain gages, resistance strain gages, vibrating wire piezometers, pressure cells, in-place inclinometer strings or ShapeAccelArrays. The readings from these devices are collected and stored on a multi-channel data logger.
Conventional readings of the applied load determined from the jack pressure gage and load cell, and deep foundation head movement determined by LVDTs, digital dial gages, or mechanical dial gages, can be combined with the instrumentation, mentioned above, to determine the capacity or nominal soil resistance, the load-transfer behavior under axial loads, or deflected shape under lateral loads.
After processing the collected load test data, GRL engineers prepare a final report summarizing the load-movement results and pile movement analysis. These results can be compared to the specified load test interpretation criteria to determine the deep foundation’s capacity or nominal resistance. Load-deformation behavior at other depths, as well as load transfer to the soil along the shaft length can also be provided depending upon the instrumentation. In lateral load tests, the deep foundation head movement versus applied load is summarized and reported. With additional instrumentation, the deflected shape versus shaft length and/or the head rotation is reported.
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.