Experimental Investigation of Unsaturated Soils and Application of the Swell Equilibrium Limit in Numerical Analysis

By: Bee Fong Lim

Abstract

Expansive soils provide a unique challenge in the field of unsaturated soil mechanics. Expansive soils can be either beneficial or damaging depending on the application where the soil has been used. For example, swelling soil can be used in a landfill liner to control the leaking of leachate taking the advantage of its low permeability and self-healing qualities. On the other hand, if swelling potential has not been considered, it can cause excessive deformations and swelling stresses on an adjacent structure constructed in the swelling soil.

The experimental investigation and analysis of unsaturated soils of my research work has been divided into three main projects: a benchmark testing comparison between the triaxial and oedometer results; laboratory testing of swelling soils under various boundary conditions; and constitutive modeling of the laboratory results. The first goal of this research is to determine the relevance of stress state conversion in unsaturated soils from a one-dimensional test to the triaxial test and vice versa. The second objective is to explore the Swell Equilibrium Limit (SEL, Siemens and Blatz 2009) with various testing conditions. The various influential factors in SEL include the following: the effects of stress history (e.g. unloading) in natural materials; the effects of stress - volume test path; and differences between natural and compacted soils. The third goal is to develop a practical analysis tool for swelling soils.