The Analysis Of Sandstone Damage Characteristics Under The Action Of Freeze-Thaw And Load

With the further advance of the country’s western development, a large number of projects will be carried out in the western cold regions, for the security of cold regions rock mass engineering, it is necessary to study the freeze-thaw properties of the rock. Based on cold regions engineering, the freeze-thaw properties of the rock were researched systematically by using the methods combining theory and experiment.An entire fresh red sandstone rock was selected in site, processed into standard cylindrical specimens, and conducted freeze-thaw cycle test of different freeze-thaw cycles(0 times, 5 times, 10 times, 20 times and 40 times), then conducted triaxial compression test of different confining pressures(0MPa, 2MPa, 4Mpa and 6Mpa). The failure forms of sandstone specimen were obtained through observing experimental phenomena, and mechanical parameters of red sandstone under conditions of freeze-thaw cycles were got by analyzing test results, as well as the change law of sandstone strength and deformation characteristics with the variation of freeze-thaw cycles and confining pressure.Taking continuum damage mechanics theory and application strain equivalence principle, the sandstone damage model were established by using Weibull statistical distribution and Poisson statistical distribution respectively based on D-P failure criteria. And their rationality verified through the test data. There were no significant differences when descripting the destruction of sandstone compression process by using the Weibull distribution and Poisson statistical distribution. But due to taking the Poisson statistical distribution, the parameter expression was more complex, so the practicality is not strong.Sandstone damage model was modified, and the changes in peaks later stage of the sandstone stress-strain curve could be better reflected by the modified model, and the sandstone residual strength descripted more exactly; Also, the physical meaning of the model parameters were analyzed and discussed; The stress state of sandstone damage model was extended from conventional triaxial stress state to true triaxial stress state, which could describe the impact of the intermediate principal stress on strength and mechanical properties of sandstone theoretically.The damage model under the action of the freeze-thaw was established under true triaxial stress state, and its rationality was proved by red sandstone freeze-thaw cycles and triaxial compression test data. When constant confining pressure, the sandstone total damage of freeze-thaw cycles and the load exacerbating with the number increasing of freeze-thaw cycles, while the sandstone plasticity increasing under the action of freeze-thaw cycles, and brittle weakened; when freeze-thaw cycles number unchanging, the total damage of sandstone with decreasing with the confining pressure growing, and sandstone plasticity enhanced.