Soil-water characteristic curve of sandy clayey purple soil under different overburden pressures

The soil-water characteristic curve (SWCC) of sandy clayey purple soil in Chongqing of China is investigated under different overburden pressures (0, 40, 100, 200 kPa) using the stress-dependent SWCC pressure plate extractor by Geo-Experts Ltd. Furthermore, the dual-stress SWCC model is used to analyze the test data. The results show that: (1) The void structure of the soil samples changes under the dual-stress rariable of overburden pressure and suction. In the process of desorption, the inflection point of purple soil’s porosity ratio change appears later under large overburden pressure. The void ratio does not change significantly in the process of absorption. (2) Under the dual-stress variable, bimodal SWCC is found at high overburden pressures (100, 200 kPa). After the desorption-absorption process, the moisture content exhibits hysteresis. (3) The dual-stress generalized SWCC model can be used to simulate the SWCC of purple soil under different overburden pressures. By combining the pore-size density function and the soil parameter S-index, the formula for the optimal volume moisture content of soil is proposed, and can be applied to the corresponding engineering construction guidance in purple areas soil.