高温后围压对花岗岩变形和强度特性的影响

利用MTS815.02电液伺服材料试验系统完成了不同温度作用后（25℃~1000℃）,不同围压下的30块花岗岩岩样的三轴压缩试验,分析了温度、围压对岩样的变形以及强度特性的影响。试验结果表明：①岩样质量随着温度的升高小幅下降,1000℃时仅比25℃时下降了0.364%;温度低于600℃时,岩样体积、密度变化不明显,温度高于600℃时,体积加速膨胀,密度减小幅度增大,1000℃时体积比25℃时膨胀了5.027%,密度降低了5.132%。②高温作用后,岩样三轴压缩应力-应变曲线大致经历了压密、弹性、屈服、破坏、软化、残余等几个阶段,岩样的刚度、峰值强度、抗剪强度、残余强度、塑性变形均随着围压的增大而增大。③岩样黏聚力随着温度的升高呈线性下降,内摩擦角随着温度的升高先增大后减小,抗剪强度随着温度的升高呈二次多项式减小关系,围压的增大削弱了温度对抗剪强度的影响。

Influence of confining pressure on deformation and strength properties of granite after high temperatures

Based on the triaxial compression tests of thirty granite samples under different confining pressures and temperatures of 25~1000℃ by MTS815.02 servo-controlled testing machine,the influence of temperature and pressure on the deformation and strength characteristics is analyzed. The test results show that: (1) The quality of rock samples decreases slightly with the increasing temperature, which decreases by only 0.364% at 1000 ℃ compared to that at 25℃. When the temperature is below 600 ℃, the volume and density have no significant change, then as the temperature rises, the volume expands with acceleration and the density decreases rapidly, and the volume expands by 5.027% and the density decreases by 5.132% at 1000℃ compared to those at 25℃. (2) After high temperature, the triaxial compression stress-strain curves of rock samples have gone through the stages of compaction, elasticity, yield, destruction, softening and residual stresses. The stiffness, peak strength, shear strength, residual strength and plastic deformation of rock samples increase with the confining pressure. (3) The cohesion decreases linearly and the internal friction angle first increases and then decreases with the increasing temperature. The shear strength shows a quadratic polynomial reduced relationship as the temperature increases. The confining pressure weakens the influence of temperature on the shear strength. This work may provide the guidance for the selection of mechanical parameters of rock in the underground geotechnical engineering.