Pile load-transfer mechanisms in expansive soils: Incorporating matric suction into load-transfer analysis

Abstract

Construction on expansive soils presents significant challenges due to the volumetric expansion and contraction associated with variations in moisture content. These soils, which are naturally found in an unsaturated state, have attracted enormous global attention because of their ubiquitous nature. The impacts of climate change further exacerbate the challenges, amplifying the problems these soils pose for construction and infrastructure. Despite extensive research on soil stabilization techniques, the challenges associated with pile foundations in expansive soils have not been investigated to the same extent. This paper seeks to explore and critically assess the role of matric suction in governing the load-transfer behavior of piles in expansive soils using a shear-deformation-based approach. Moisture variation-induced pile uplift (or downdrag) is governed by pile-soil friction, normal stress, and swelling-shrinkage-induced displacement, while the nonlinear soil response is commonly represented using hyperbolic models. The discussion focuses on integrating pile-soil relative displacement, matric suction variations, and interface shear parameters into analytical models to predict pile load-displacement behavior in unsaturated expansive soils. These models account for suction-dependent nonlinearity in shear strength and stiffness.