Immersion tests on PHC piles in collapsible loess

The static load tests are adopted to investigate 2 PHC tubular piles in collapsible loess site under natural, pre-soaked and post-soaked soil conditions. Based on the additional settlement of piles during water immersion and stress tests in the process of static load tests, the bearing capacity behavior, axial force and lateral friction are analyzed. The test results show that there is no occurrence of negative skin friction under water immersion condition, and the additional settlement of the piles does not result from negative skin friction triggered by the self-weight collapse settlement. The transfer of axial force is slow from ground to the depth of 6 m, which behaves vertical line, and is nonlinear at the lower part of the piles. The curves of lateral friction varying with depth have different anti bending points. The difference between the upper part and lower part of the piles at anti bending points is clear. Local envelope zone appears under the ultimate load.