Collapse Behavior of Compacted Clay in a Water Content-Controlled Oedometer Apparatus

Assessing soil deformation leading to collapse is often conducted through a suction-controlled method, which can be time-intensive. In this study, the collapse deformation of compacted clay was investigated by conducting time-saving and convenient water content-controlled tests. The compacted clay specimens, each with a unique initial void ratio, were subjected to water retention experiments. The water content-controlled oedometer apparatus performed tests involving compression, wetting, and subsequent recompression. Observed experimental results indicate that water content has an inverse relationship with suction, with suction increasing as water content decreases, suggesting an inverse relationship between the two variables. In compression tests performed at a constant water content, water saturation increases and suction decreases as the void ratio decreases. Wetting leads to a decrease in void ratio as the saturation level rises, gradually declining along the wetting path until it aligns with the compression line of fully saturated soil. The compression lines at varying suction levels are established through theoretical analysis of water retention and water content-controlled compression test results. In addition, the collapse deformation is well predicted with a concise formula related to pore gas saturation. In this way, this study provides a quick and effective method for evaluating the hydro-mechanical properties of unsaturated soils.