A novel soil-water characteristic curve prediction model for unsaturated soil considering pore structure characteristics

The soil-water characteristic curve (SWCC) graphically describes the significant hydraulic characteristics of unsaturated soil seepage. Several factors influence the SWCC of unsaturated soil, including temperature, void ratio, pore characteristics, particle composition, and load, with soil pore structure exerting a pivotal influence on SWCC. This study aimed to analyze the influence of pore structure on the SWCC of loess. The results showed that the shape of SWCC of loess is similar with varying pore structures under a fixed void ratio, with discrepancies in the air entry value(AEV) and decline sections. The void ratio of macro pores of intact loess exceeded that of remolded loess, in turn resulting in a larger AEV. There were fewer small pores and middle pores in the intact loess sample, whereas the remolded loess showed a greater decline rate after transitioning into an the unsaturated state. On the other hand, an increase in the size of the pores was observed in the loess following the drying-wetting cycles, whereas the number of smaller and middle-sized pores decreased. Similarly, there was an increase in AEV of loess following the drying-wetting cycles, with the gradual deceleration in the rate of decline in the unsaturated stage. The pore state parameters and fractal dimension of pore size distribution(PSD) were introduced into the V-G model based on the experimental results, with deriving a modified V-G model. The intact loess was predicted by remolded loess, and the loess after the drying-wetting cycles were predicted by loess before the drying-wetting cycles. The results showed that the modified V-G model is more effective in predicting the SWCC of intact loess and loess after the drying-wetting cycles.