Load Testing Helical Piles

The purpose of load testing a helical pile is to determine the ultimate load of the pile with minimal deflection and to verify the Kt factor of the pile. This is the only way to know if the pile will actually carry the designed ultimate load.

There are three common types of load test: Compression per ASTM D1143, tension load per ASTM D3689, and lateral load test per ASTM D3966. Most load tests are performed to a factor of safety of two times the published service/working load.

The testing procedure for a load test typically involves installing the test pile, installing 2 or 4 reaction anchors, setting cribbing into place, putting the load beam onto the cribbing, placing the reaction beams, and connecting the load beam to the reaction beams.

A calibrated hydraulic jack and cylinder are used to load the pile. The cylinder is placed on top of the pile and pressured against the bottom of the load beam. Once the reaction anchors have been loaded, the cylinder attempts to drive the pile down, and the pile is loaded in 20% increments. After each increment, the movement of the pile is recorded with dial gauges. Once the ultimate load has been reached, the pile is downloaded in decrements to the alignment load, and the total deflection of the pile is recorded. If the pile does not exceed the total deflection criteria for the project, the installation of the piles can begin. If a pile fails, it will need to be redesigned and tested again.