Visco-Elastoplastic Soil Model for Irregular Shear Cyclic Dynamic Loadings

The visco-elastoplatic soil model, introduced in this paper, is consistent with the experimental relationships, such as shear modulus vs shear strain, damping ratio vs shear strain, pore pressure ratio vs cycle ratio and stress ratio vs number of liquefaction cycles, etc. The loading-reloading rules control the hysteresis loops beneath skeleton curve. The "apparent applied forces"method is suggested to evaluate the effects of soil viscosity. The generations of pore pressure are evaluated by"fraction cycle method", which is simple and effective, especially for waved increases of pore water pressure.The soil model have been applied to a computer program （SRHSL-1978） for the total stress analysis of seismic response of site soil.