Numerical simulation of the uplift bearing behavior of pile foundations for transmission towers in expansive soil area

Abstract

Piles are commonly used as foundations for power transmission towers located in expansive soil areas. The strength of expansive soil is highly sensitive to the changing water content, which complicates the pile–soil interaction. In this study, a 3D elastoplastic finite element analysis of a typical pile foundation for a transmission tower in an expansive soil area was conducted to understand the effect of water content in expansive soil on the uplift bearing capacity of the pile foundation. The results that the failure mode of the pile foundation is almost unaffected by the water content. Shear failure was observed at the pile–soil interface, and, when the pile was pulled out, it lost its uplift bearing capacity. With the increasing water content of the soil, the ultimate uplift bearing capacity of the pile foundation exhibited a significant decreasing trend, whereas the displacement of soil around the pile became remarkable. The distribution of pile axial force and lateral frictional resistance during the uplift process was also evaluated. The pile axial force decreased gradually and at a higher rate with increasing depth. Once the pile reached the ultimate uplift bearing state, the pile lateral friction increased almost linearly with depth.