Pore-scale model for estimating the bimodal soil-water characteristic curve and hydraulic conductivity of compacted soils with different initial densities

This paper proposed a pore-scale model to simulate the effect of initial soil density on the bimodal soil water characteristic curve (SWCC) of compacted soils. The pore-scale model is developed based on the bimodal pore size distribution. Soils with bimodal pore-size distribution is assumed to have dual porosity, namely the macropore structure and the micropore structure, and hypothesized that the micropore structure is hard to be compressed under mechanical loading. The water stored in the macropore structure is divided into two parts, the bulk water and the meniscus water, respectively. The deformation of soil (bulk water flow) is obtained by horizontal shifting and vertical scaling of the pore-size distribution (PSD) function. A toroidal model is used to describe the influence of initial density on the meniscus water. The pore structure of compacted coal gangue was qualitatively imaged as an evidence of the pore structure changes, and the SWCC of the compacted coal gangue was quantitatively analyzed. Finally, a numerical method is advised for simulating bimodal permeability function by using the proposed model with Mualem function. Laboratory test results in published literature are employed to validate the proposed model and permeability function, and the model predictions showed good agreement with the experimental data in the literature.