LABORATORY BASED PARAMETRIC STUDY ON THE SWELL RESPONSES IN EXPANSIVE VERTOSOLS

Abstract

Expansive grey Vertosols are predominant in Australia, especially in Queensland. These soils
induce a significant amount of swell strain on the lightweight structures founded on/in these soils when soil
moisture changes due to climatic influence. According to AS2870: Residential slab and footing design code
(AS2870, 2011) and available literature, active zone depth which contributes to the climate induced-soil
displacement in Queensland can be up to 5m. To design lightweight structures founded within the active zone
depth, it is imperative to understand swelling behavior of expansive grey Vertosols. The resultant swell strain
of these expansive soils is primarily a function of initial water content or initial soil suction and overburden
pressure (surcharge). However, there is an extremely limited amount of data available for unsaturated swelling
characteristics of expansive soils in Queensland. In this study, a series of conventional oedometer tests were
conducted to investigate the effect of the initial water content, initial soil suction and the surcharge on the
swelling behavior of expansive grey Vertosol that is predominant in South-East Queensland. The swell strain
of expansive grey Vertosol displayed greater sensitivity to surcharge when compared to initial water content
or suction. Developed relationship between swell strain per unit change in volumetric water content and
surcharge depicted statistically strong (R2 = 0.89) agreement. The application of the knowledge gathered from
this study will benefit the decision making in semi-arid regions when building lightweight structures on grey
Vertosol.