Soil-water-air coupled finite element analysis on slope failure in unsaturated soil

In this paper, a program of finite element method named as SOFT, using finite element-finite difference scheme (FE-FD) in soil-water-air three-phase coupling problem has been developed based on a rational constitutive model for unsaturated soil proposed by Zhang and Ikariya (2011), which can properly take into consideration of moisture characteristics of unsaturated soils. In the program, the FEFD formulation in saturated condition proposed by Oka et al. (1994) has been extended to unsaturated condition. In order to verify the availability of the program, a model test on slope failure of unsaturated soil, carried out by Kitamura et al. (2007), is simulated by the proposed numerical method. From the results, it is known that the test results can be described in a satisfactory accuracy on the whole.