A macroscopic model for predicting the relative hydraulic permeability of unsaturated soils

A macroscopic model for predicting the relative hydraulic permeability of unsaturated soils is proposed. In this model, pores in unsaturated soils are considered to be parallel flow tubes. The water flow in the pores is assumed to take place in the water film on the inside wall of the flow tubes. The viscosity of pore water is considered to be different from the viscosity of pure water and variable with the variation of degree of saturation. The values of tortuosity factor and pore shape factor of unsaturated soils are estimated theoretically. The theoretical model is verified using experimental data for 32 different soils. For application in engineering practice, the value of viscosity of pore water in different soils is proposed.