Abstract: The dynamic responses of saturated soil are the always concerning problems of soil dynamics. The liquefaction caused by cyclic loadings often increases the pore pressure and decreases the strength of the soil. In addition, for the site with large size saturated soil, large numbers of degrees of freedom often lead to low calculation efficiency, and restrict the development of the numerical method of saturated soil. Therefore, the proposed fully explicit finite element method for the equations of saturated porous medium in u-p formulation is implemented into the OpenSees software. By using the element and constitutive models in OpenSees, the efficient and explicit computation of the dynamic responses of saturated soils can be realized in this paper. In a two-dimensional saturated model, the elastic dynamic responses obtained from the Newmark method are compared with the results obtained from the embedded method. Two results are in good agreement, which verify the embedded algorithm. The proposed algorithm is used to compute the nonlinear free field seismic responses of the seabed soil. This method simulates liquefaction process, failure modes and the lateral deformation of the seabed soil effectively. The proposed algorithm illustrates significant advantages in terms of computational efficiency.

Key words: OpenSees, saturated porous media, completed explicit finite element method