Mechanical properties of sandstone at triaxial compression subjected to coupling temperature and pressure

High ground temperature and geo-stress are difficulties encountered in current deep rock mass engineering development. However, research materials on the strength and deformation of rock mass from room temperature to 100 ° are limited. Triaxial compression experiments subjected to coupling temperatures at 25 °, 50 °, and 75 ° and confining pressures at 10, 20, and 30 MPa, respectively, were conducted on sandstone from Chongqing Beibei mining area by adopting the rock multi-field coupling triaxial instrument to reveal the mechanical properties of sandstone and its changes and laws of physical parameters under the influence of temperature. The stress strain curve, failure load, average modulus, peak strain, cohesion, and internal friction angle of sandstone were obtained based on the indoor experiment result analysis. Moreover, the influence of temperature and pressure coupling interaction on the physical property and deformation mechanism of sandstone were revealed by analyzing the parameters of mechanical properties. Results show the following: (1) The failure process of sandstone due to coupling temperature and pressure is generally consistent with the stress- strain curve of conventional triaxial compression, and the failure mode is shear failure; (2) When temperature is constant, the failure load increases with confining pressure(a high temperature leads to the rapid increase in confining pressure growth rate); when confining pressure is constant, the failure load influenced by temperature exhibits complex effects related to coupling temperature and pressure; (3) When temperature rises, the average modulus of sandstone first increases then reduces with increasing confining pressure; when the confining pressure is constant, the average modulus reduces along with increasing temperature; (4) The axial peak strain increases with temperature and confining pressure; (5) Cohesion and internal friction angle decrease with increasing temperature, and the weakening effect on cohesion due to temperature increase is larger than that on internal friction angle. This study provides references to explain coupling temperature and pressure issues of rocks in temperature ranging from room temperature to 75 °. © 2019 Eastern Macedonia and Thrace Institute of Technology.