A Study of Kinematic Interaction between Soil and Pile in Bangkok's Subsoils

Abstract

Loading on pile foundations during earthquakes can be divided into two types, namely, the inertial and the kinematic forces. The inertial force occurs by the acceleration of the mass of a superstructure with respect to its foundation. The kinematic force occurs when a pile is displaced by surrounding ground. In Thailand, the responses of piles get little attention, but in other countries, such as IBC2021, kinematic forces must be considered in pile design. The study aims to determine the response of piles in the Bangkok soft clay basin with respect to the kinematic forces and to compare the computed internal forces with those determined by the equivalent static force. Additionally, various simplified formulae in literatures are also reviewed and evaluated by comparing their predictions with those obtained from 3D finite element analyses. The results show that kinematic forces produce smaller internal forces in piles than inertial forces, but cause significant increases in bending moments at the boundary between the Bangkok soft clay layer and the stiff clay layer, requiring sufficient steel reinforcement at this location. The induced moment due to kinematic forces can be approximately estimated by a simplified formula with a 20% error compared to 3D FEA.