Experimental Characterization And Constitutive Modeling Of Partially Saturated Clay Under Dynamic Loading Conditions

As one of the most common geological material, soil is widely used in various civil and defense engineering constructions. Soil foundation and infrastructure built upon the soil basement, in addition to bear the normal static loading, but often have to endure such as impact, shock, explosion and other strong dynamic loading.Clay is widely distributed globally, and is in a partially saturated state under normal conditions. Partially saturated clay is an extremely complex mechanical property of materials. So far, the research on constitutive relationship of partially saturated clay, especially when partially saturated clay under extreme dynamic loading, is still incomplete.The dynamic mechanical properties of partially saturated clay are affected by many factors, including the initial density(compaction), moisture content(saturation) and external load characteristics(stress level, loading rate) and so on. To investigate the influence rules of these factors, a series of static and dynamic mechanical experiments are carried out for partially saturated clay specimens with different initial mass densities, moisture contents.Among them, the static mechanical experiments are including unconfined compression test and triaxial shear test; the dynamic mechanical experiments are including uniaxial compression SHPB test, passive confining pressure SHPB tests and plate impact experiments. Through the analysis of the experiment results, partially saturated clay in static and dynamic loading conditions of mechanical characteristics are obtained. In addition, the influence rules of initial mass density, moisture content and external load characteristics and other factors are studied.A viscoplastic cap model of the Perzyna type is proposed to describe the yield and failure behavior of partially saturated clay. Besides, the p-a equation of state and a modified equation of state of three-phase mixture are proposed combine to describe the pressure-density relationship of partially saturated clay under high pressure. Furthermore, a method of determine the parameters of the viscoplastic cap model and equation of state are introduced, which based on the static and dynamic mechanical experiment results of partially saturated clay.To validate the applicability and accuracy of the proposed viscoplastic cap model and equation of state for partially saturated clay and its parameters, the viscoplastic cap model of the Perzyna type and the equation of state including p-a equation of state and a modified equation of state of three phase mixture are implemented in LS-DYNA software as a user-defined material and user-defined equation of state subroutine respectively.In addition, the simulations of dynamic process of partially saturated clay are carried out by using the LS-DYNA software. It is concluded that the proposed model and its parameters are adequate for describe the dynamic behavior of partially saturated clay.