Main factors affecting soil-water characteristic curve

In this research, an experimental study was carried out by performing a series of wetting tests on compacted clay with the initial density being controlled. The tests were conducted under isotropic stress, triaxial compression and extension stresses respectively by using an unsaturated triaxial testing apparatus. The main purpose is to evaluate the effects of the stress-history, stress state, pore size and its distribution, and void ratio on the soil-water characteristic curve (SWCC). The results clearly indicate that void ratio is a direct and important factor affecting the SWCC for given soils while both the stress-history and stress state are indirect factors. In addition to triaxial tests, a series of drying tests were also conducted, by using the pressure plate apparatus, on the pre-consolidated and compacted specimens with the same void ratio but different pore size distributions. The testing results show that two specimens have different SWCC even through their densities are almost the same, which indicates that for a given soil, the main factor affecting the soil-water characteristic is the pore fabric that can be expressed simply by void ratio and the pore size distribution.