Abstract：The bounding surface plasticity constitutive model of soil is introduced. An self-adaptive multistep integration procedure in conjunction with local iteration and radial return is employed in numerical implementation of the bounding surface model. The dynamic differential equations of the saturated-porous media are discretized in spatial and temporal using the lumped-mass finite element model and explicit integral method. Considering the bounding surface plasticity constitutive model of soil，the program，named as WSDP，is coded to analyse the dynamic elastoplastic responses of two-dimensional soil layer. The influences of the constitutive models of soil，the stress history states of soil，the artificial boundary and viscous damping are considered when the dynamic elastoplastic responses of soil layer are computed using the coded program. The following conclusions can be drawn. (1) The amplitude of elastoplastic displacement becomes larger than that of elastic case；and the duration of elastoplastic response becomes longer than that of elastic case；(2) The results for the cases of different coefficients of lateral earth pressure K are computed，respectively. The comparison of the results shows that the displacement response is delayed；the amplitude of Fourier spectrum is increased，and the component of high frequency is decreased with the decrease of K. (3) The computing accuracy satisfies the requirement when the dynamic elastoplastic responses of soil layer are analyzed by the artificial boundary. (4) The influence of damping ratio that eliminates the high-frequency oscillation on the dynamic elastoplastic responses of soil layer is not obvious if the damping ratio is confined to a limited range. It will be effected by the accuracy of result if the value of damping ratio is not proper.
