Abstract
Pile foundations are widely used in both saturated and unsaturated soils. In certain scenarios, these foundations are subjected to combined vertical and lateral loads. Conventionally, saturated soil mechanics principles are routinely used for the design of pile foundations in unsaturated soils. Such approaches contribute to unreliable estimates of the behavior of piles due to ignoring the influence of matric suction. In this paper, a comprehensive numerical technique is proposed for simulating the behavior of single piles subjected to combined vertical and lateral loads in unsaturated soils by taking account of the nonlinear behavior of shear strength and the elastic modulus of unsaturated soils. This is achieved through a subroutine that was developed for use in the ABAQUS software. The proposed numerical method provided reliable prediction of the vertical load-displacement behavior of a published model pile tested in saturated and unsaturated sands. In addition, 3D finite element analysis was extended to simulate the influence of variations in ground water table (GWT) on the vertical bearing capacity and the influence of vertical loads on lateral response of piles. The proposed numerical technique is a promising tool for implementing the state-of-the-art understanding of the mechanics of unsaturated soils into conventional engineering practice.
Highlights
Pile foundations are typically long slender axial columns embedded into the soil to carry large loads safely from the superstructure to the soil below and significantly limit the settlements
A comprehensive numerical technique is proposed to simulate the load-displacement behavior of piles in saturated and unsaturated soils under both vertical and lateral loads
This is achieved by introducing a user subroutine USDFLD into ABAQUS to describe the nonlinear behavior of shear strength and modulus of elasticity of unsaturated soils
Summary
Pile foundations are typically long slender axial columns embedded into the soil to carry large loads safely from the superstructure to the soil below and significantly limit the settlements. Pile foundation designs are conventionally based on principles of saturated soil mechanics, ignoring the influence of matric suction in unsaturated soils. Due to this reason, both the pile load carrying capacity and their settlement behavior may not be reliably estimated. To the best of the knowledge of the authors, three-dimensional (3D) numerical modeling studies are not undertaken to predict the loaddisplacement behavior of piles in unsaturated soils taking account of the combined influence of vertical and lateral loads. The first objective was directed towards predicting the behavior of single piles subjected to vertical loading in sand under saturated and unsaturated conditions taking account of the influence of matric suction. The shear strength of unsaturated soils may increase, decrease or remain constant depending on the type of soil
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