Pore network investigation on hysteresis phenomena and influence of stress state on the SWRC

The soil-water retention curve (SWRC) is the relationship between the suction values and water content of the soil. This curve has one or more branches depending on the suction imposition paths, and represents one of the most important properties of unsaturated soils. In this paper, by using a percolation approach and introducing a trial-and-error process, a randomly distributed pore network model is first calibrated using experimental data corresponding to the main drying branch of the SWRC. The influence of the stress state on the pore-size distribution of the network is further studied. The calibrated network model is used to predict the main wetting and scanning branches of the SWRC. Piston-type and cooperative fillings are used as the two wetting mechanisms. The proposed method facilitates modeling pore networks with large numbers of pores covering a wide range of suction values (full saturation through the residual degree of saturation). The results indicate that with an increase in the applied stress, micropores and macropores are affected. However, it is the change in the macropores that strongly influences the SWRC. Also, it is possible to predict the wetting and scanning branches of the SWRC with reasonable accuracy once the model is calibrated when using the main drying curve.