Ultimate Lateral Resistance of Piles in Soils Based on Active Pile Length

Abstract

Simulation of the in situ behavior of pile foundation is necessary in the seismic design and assessment of piles for target structural integrity and performance during earthquakes. Having the mere presence of the soil and the pile in this foundation system, the complex behavior of piles is generally captured by the soil-pile interaction. In this research, a simple parameter called the active pile length, L _a, which is reflective of the deformation of pile relative to the stiffness of the soil, is explored to describe the ultimate lateral resistance of the soil. The idea is based upon the deformation of flexible piles commonly used in engineering practice. When piles are induced by a lateral load, the pile deforms significantly in the region near the ground surface and decreases with increasing depth. This region of significant deformation down to the negligible point along the pile depth is defined as the active pile length, L _a. During the event of nonlinear excitation, a soil wedge is formed in the passive region along this active pile length. This soil wedge is indicative of the ultimate side soil resistance, and thus can be inferred to be described by L _a. To simply investigate, a simple plane strain condition using 2-D finite element method in nonlinear analysis is done to obtain the behavior response of a single pile embedded in a homogeneous soft soil. The elasto-plastic behavior of the soil is modeled using the subloading t _ij model and the pile is modeled as a 2-D continuum based beam element. Deformation of the pile and corresponding surrounding lateral soil deformation are analyzed. The potential of this simple concept of active pile length to describe the nonlinear response of piles embedded on soft soils is presented for more practical approach in the seismic design and assessment of piles.