Dynamic Experiments And Numerical Simulation Of Frozen Soil

Frozen soil is a compound dielectric material consisted of solid particles, ice crystals, liquid water and gas inclusions (mainly water and air). The essential difference between unfrozen soils is the existence of ice crystals. Frozen soil area is widely distributed in our country. In recent years, because of the economic development of our country, a series of major projects will be carried out in frozen soil regions. Structures would impact on dynamic loadings inevitably. So, it is necessary to study the dynamic mechanical properties of frozen soil.Using the diameter of 30mm split Hopkinson pressure bar (SHPB), two kinds of experiments (uniaxial loading and confining pressure loading) on frozen soil of different temperature under different strain rate dynamic loadings were done. The range of temperature is from-3℃ to-28℃. The range of strain rate is from 300S-1 to 1500S-1.Frozen soil shows obvious strain rate effect and temperature effect. The peak stress and final strain of stress-strain curve would increase with increasing strain rate. The peak stress would increase with the decreasing temperature and the final strain would converge. Based on the HJC constitutive model, the dynamic mechanical properties under impact loading was analyzed. The SHPB experiments of frozen soil were simulated using the finite element analysis software LS-DYNA and the simulation results were similar to the experiment results. Destruction process of frozen soil were studied, and also the propagation process of stress wave in the incident bar, transmission bar and frozen soil specimen.Under the passive confining pressure dynamic loadings, in addition to the obvious strain rate effect and temperature effect, frozen soil can also shows obvious confining pressure effect. The peak stress of stress-strain curve under passive confining pressure is significantly greater than uniaxial loading. Besides, frozen soil under passive confining pressure shows the elastic-plastic characteristics. Its stress-strain curve has a drop before rising process. Based on the HJC constitutive model, the passive confining pressure SHPB experiments of frozen soil were simulated and the simulation results were similar to the experiment results. The effect of different material and size of the sleeve on peak stress were analyzed. The research shows that the peak stress would increase with the increasing sleeve and specimen elastic modulus ratio and increasing thickness radius ratio. Through the constant pressure in radial direct sample method to simulate the active confining pressure effect. The results show that, with the increasing active confining pressure value, the peak stress would increase and ratio absorbing energy would decrease.