Date of Award

Spring 1-1-2011

Document Type


Degree Name

Doctor of Philosophy (PhD)

First Advisor

Dobroslav Znidarcic

Second Advisor

Shideh Dashti

Third Advisor

Hon-Yim Ko

Fourth Advisor

John McCartney

Fifth Advisor

Howard Perko


This research presents experimental investigation of swelling mechanisms of a highly expansive soil. The amount and rate of volume change for highly expansive material was studied by considering several variables such as; relative humidity, liquid water, soil suction and wetting rate. The swelling pressure development was investigated by restricting lateral and axial deformations under oedometric conditions. The test results were analyzed in framework of several constitutive relationships and used to investigate time-dependent one-dimensional swelling in terms of coefficient of volume compressibility, coefficient of permeability and coefficient of hydraulic diffusivity. To achieve the research objectives, particular tasks included: (1) investigation free shrinkage-swelling behavior by controlling the aforementioned variables; (2) measuring the swelling pressure by performing constant volume oedometer test and one-dimensional swelling test; and (3) the experimental results were analyzed in order to determine the rate of swelling. Based on experimental results, the actual swelling was occurring at degree of saturation higher than 80%. Under 80% saturation, the volumetric expansion due to suction reduction was taking place. The soil suction change in the range higher than 1 MPa had minimal effect on the volume change due to the stiffness of the expansive soil as opposed to that in the range lower than 1 MPa. The constant volume swelling pressure test results indicated that the swelling pressure increased as the initial water content decreased due to the suction dissipation. The rate of swelling at higher void ratio may not be only controlled by hydraulic conductivity but rather by the ability of the highly expansive clay material to absorb water.