Finite element analysis of short piles in expansive soils

A two dimensional axisymmetric finite element based model for analysis of a soil-pile system in expansive soils is developed. The pile is assumed to behave as linearly elastic while the soil is modelled as nonlinear elastic material. Swelling and shrinkage of the soil are related to change in soil suction. The predictions of the model are compared to the results of field experiments from two expansive soil sites in Sudan, Wad Madani and Elfao. The predictions of the numerical model are in good agreement with field results. Parametric studies are performed using the model. The study shows that increase in pile length decreases the upward vertical movement of the pile. As the axial load increases, both the upward vertical movement and the tensile stress decreases and eventually the pile may be subjected only to downward movement and compressive stresses. Tensile stresses for loaded piles occur throughout most portions of the pile within the active zone with the maximum stress developing near the mid height of the pile.