1. State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing　 400030,China; 2. College of Resources and Environ- mental Sciences,Chongqing University,Chongqing　 400030,China;3. State and Local Joint Engineering Laboratory of Methane Drainage in Complex Coal Gas Seam,Chongqing　 400030,China

基于自主研发的"多功能真三轴流固耦合试验系统",进行了真三轴应力(σ1﹥σ2﹥σ3)条件下,保持体应力不变、改变中主应力系数的砂岩强度试验,探讨了不同中主应力系数条件下砂岩的变形、强度及剪切破坏特性。试验结果表明:在真三轴应力条件下,扩容起点随中主应力系数b的增大而呈递减趋势。应力加载过程中扩容存在明显的阶段性:随最大主应力的增加,稳定压缩段,体应变近似呈线性递增趋势;加速扩容段,体应变近似呈二次函数增大,且应变速率呈线性增大。保持体应力不变条件下,砂岩峰值强度随中主应力系数b的增大而逐渐降低,符合修正Lade准则。试验应力条件下,岩样主要发生双斜面对称剪切破坏,剪切破坏面倾角随b的增加呈线性增大。

Based on the self-made “ multi-functional true triaxial fluid-solid coupling experiment system”,an experi- ment to investigate the strength of sandstone under true triaxial compression(σ1 ﹥ σ2 ﹥ σ3 )for different coefficients of the intermediate principal stress and maintaining the volume stress unchanged was carried out. The authors have dis- cussed the deformation,strength and shear failure plane feature of sandstone under different coefficients of intermediate principal stress. The research result shows that the starting point of dilatancy decreases with the increase of the coeffi- cient b of intermediate principal stress under true triaxial compression. The dilatancy exists an obvious stage under ex- perimental conditions,with the increase of maximum principal stress,the volume strain increases linearly at the steady compressing stage and increases as a quadratic function at the accelerating stage with the strain rate increases linearly. The strength of sandstone decreases with the coefficient b increase and coincides with the Modified Lade Criterion un- der the condition of keeping volume stress unchanged. In this experimental test,the rock specimens generally devel- oped a typical type of symmetrical double shear failure and the angle of shear plane increases linearly with the coeffi- cient b increase.

国家自然科学基金资助项目(51434003,51374256)；2016重庆市科研创新资助项目(CYS16012)；

Yin Guangzhi,Lu Jun,Li Xing,et al. Influence of intermediate principal stress on dilation and strength characteristics of sandstone[ J]. Journal of China Coal Society,2017,42(4):879-885.