Study on one-dimensional fluid-solid coupling process in unsaturated soils under rainfall

Rainfall is a major contribution factor to landslide, and it is a typical fluid-solid coupling process in unsaturated soils. So, the study on this process in unsaturated soils is of great significance in both theory and practice. Based on two stress variable theory of unsaturated soils proposed by Fredlund, continuity equation of water and Darcy's law, the governing equation of one-dimensional fluid-solid coupling process in unsaturated soils is derived. The analytical solution of the governing equation under rainfall is gained by applying the Laplace transform and its inverse transform to it. Finite difference code is developed for solving the governing equation; the numerical solution of it is derived. Take rainfall infiltration in infinite soil layer for instance, the results of analytical solution are compared with numerical one. The result shows that: the results of the two are coincidence, the analytical solution and the finite difference code are correct; the analytical solution has the advantages of being simple in calculation; the research results can be used to predict the pore water pressure distribution over time and space and ground settlement under large-scale rainfall.