Wetting-Induced Collapse Behavior of Unsaturated Soils in Disturbed State Concept Framework

This paper presents a model for compression and wetting-induced collapse behavior of unsaturated soils using the disturbed state concept. The volume change and collapse behavior of unsaturated soils were described using their compression behaviors in two reference states, including unsaturated condition before collapse as an initially intact state and saturated condition after wetting-induced collapse as a fully adjusted state. Using a disturbance function derived from experimental results, the collapse behavior of the soil was related to its behaviors in two references states. A power form function was proposed to describe the volume change of the soil during the collapse stage. Using a piecewise continuous disturbance function, the compression and collapse behavior of unsaturated soil could be expressed in the full range of loading, including before-collapse, during-collapse, and after-collapse stages in the effective stress and net stress space. A series of laboratory tests were conducted on three different types of collapsible soils to verify the proposed model. Verification of the model with laboratory results and the data available in the literature showed the ability of the proposed model to describe the compression and the wetting-induced collapse behavior of unsaturated soils before, during, and after the wetting-induced collapse.