Development of Piping Analysis Method for Embankment Including Time-Dependent Change in Permeability Coefficient

The permeability of a saturated porous medium is regarded as a constant during the seepage process in traditional seepage analysis theory. However, it changes constantly during the piping process. This study will consider the porosity dependent changes in the permeability of a saturated porous medium during piping. The critical hydraulic gradient of piping will be deduced and the relationship between the permeability coefficient and the porosity will be considered using Kozeny–Carman's formula during the piping process in this study. The transient seepage finite element program will be applied to simulate the initial seepage field, and then whether the piping occurs in the elements will be judged. The relationship between the seepage flow and the sediment content will be used to calculate the sediment loss quantity in the piping element, and the change of the porosity in the piping element will be further calculated. Moreover, the permeability coefficient of the piping element will be adjusted according to the formula between the permeability coefficient and the porosity. With the repetition of the aforementioned process, the piping process will finally be achieved. By comparing the numerical example with the experimental result, the validity of the proposed method will be verified.