Effect of threshold suction on the prediction of the permeability function by using the statistical method

The statistical method is commonly adopted by many researchers for the estimation of the permeability function of unsaturated soil. The statistical method is developed based on the assumption that the pores are randomly connected to each other. Water can only flow through the water phase in those pores. In other words, the statistical method is only applicable when the water phase in soil is in a continuous condition. However, past studies indicated that the water phase in unsaturated soil became discontinuous when the soil suction goes beyond the residual suction. When the water phase is discontinuous, the water in some of the pores may not be able to provide the flow path because water cannot flow into the surrounding pores. Therefore, there will be a threshold suction where the statistical method becomes inapplicable for suctions beyond this threshold value. In this parametric study, the effect of the threshold suction on the estimated permeability function obtained from the statistical method was investigated.