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利用自主研发的煤岩剪切–渗流耦合试验装置,开展法向应力为2.0 MPa,孔隙水压分别为1.0,2.0和3.0 MPa条件下砂岩剪切破坏试验,同时利用三维立体扫描仪对剪切断裂面进行扫描,运用Matlab软件编写统计参数计算程序,分析不同孔隙水压下的剪切断裂面特征。研究结果表明:(1)孔隙水压对砂岩剪切力学特性具有“软化”效应,孔隙水压越高,砂岩的抗剪强度越低,峰值剪切变形量与峰值法向变形量均越小;(2)孔隙水压越高,试件剪切断裂面各点相对基准剪切面垂直距离的均方根偏差S_q、粗糙度指数S_r以及表面裂纹分形维数D_r等均越小,表明随孔隙水压增大,剪切断裂面粗糙程度降低;(3)通过剪切断裂面裂纹扩展分析发现,在不同孔隙水压条件下的剪切试验过程中,试件表面裂纹的扩展只能反映靠近该表面很小范围的内部裂纹扩展情况,不能等同试件剪切断裂面裂纹的扩展路径。
Using self-developed coal-rock shear-seepage coupling test device, the sandstone shear failure test under normal stress of 2.0 MPa and pore water pressure of 1.0, 2.0 and 3.0 MPa respectively was carried out. At the same time, The fracture surface was scanned. The statistical parameters calculation program was prepared by Matlab software, and the shear fracture surface characteristics under different pore pressures were analyzed. The results show that: (1) pore water pressure has a “softening effect” on the shear mechanics properties of sandstone. The higher the pore water pressure is, the lower the shear strength of sandstone is. Both the peak shearing deformation and the peak normal deformation (2) The higher the pore water pressure is, the smaller the root mean square deviation Sq, the roughness index S_r and the surface crack fractal dimension D_r of each point of the shear fracture surface relative to the reference shear surface are. It shows that with the increase of pore water pressure, the roughness of shear fracture surface decreases. (3) By the crack propagation analysis of shear fracture surface, it is found that in the shear test under different pore pressures, Can reflect the small extent of the internal crack propagation close to the surface and can not be equated with the extended path of the cracked fracture surface of the specimen.