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通过颗粒流程序(PFC)细观参数敏感性分析与完整红砂岩在常规三轴压缩下的试验结果,获得一组能够真实反映完整红砂岩宏观力学行为的细观参数。在此基础上,对断续双裂隙红砂岩在不同围压作用下进行颗粒流模拟,分析围压以及岩桥倾角对断续双裂隙红砂岩强度破坏特征的影响规律,揭示断续双裂隙红砂岩在不同围压作用下裂纹扩展的细观力学响应机制。研究结果表明:与完整红砂岩相比,断续双裂隙红砂岩峰值强度参数显著降低,且降幅与岩桥倾角β密切相关,黏聚力和内摩擦角均随着岩桥倾角β的增大呈非线性变化。当断续双裂隙红砂岩β=0°和30°时,两者裂纹扩展模式相近,裂隙1和2之间无贯通;当β=60°和90°时,两者裂纹扩展模式相近,裂隙1和2之间出现一处贯通;当β=120°时,在低围压下裂隙1和2之间出现两处贯通,在高围压下只有一处贯通。当应力增大到一定程度之后,颗粒之间黏结断裂,微裂纹不断产生、汇集和贯通,最终形成宏观裂纹,使得试样发生失稳破坏。围压的增加在细观上提高了颗粒之间的接触力,在宏观上表现为强度增大。高围压的存在限制了微裂纹的扩展速率。
A set of mesoscopic parameters that can truly reflect the macroscopic mechanical behavior of the intact red sandstone is obtained through the analysis of the micropore parameter sensitivity of the particle flow program (PFC) and the test results of the intact red sandstone under conventional triaxial compression. On this basis, the particle flow simulation of intermittent double-fractured red sandstone under different confining pressure was carried out to analyze the effect of confining pressure and rock slope inclination on the strength failure characteristics of intermittent double-fractured red sandstone. Meso - mechanics response of sandstone to crack propagation under different confining pressure. The results show that compared with the intact red sandstone, the peak intensity parameters of the fractured red fissure red sandstone decrease obviously, and the declination is closely related to the rock slope β. The cohesion and internal friction angle increase with the increase of the rock slope β Nonlinear changes. When intermittent double-fractured red sandstone is β = 0 ° and 30 °, the crack propagation modes are similar and there is no continuity between cracks 1 and 2. When β = 60 ° and 90 °, the crack propagation modes are similar, A penetration occurs between 1 and 2; when β = 120 °, two penetrations occur between cracks 1 and 2 at low confining pressure and only one penetration at high confining pressure. When the stress increases to a certain extent, the bond between the particles breaks, micro-cracks continue to produce, pool and through, eventually forming macro-cracks, making the sample instability damage. The increase of confining pressure improves the contact force between the particles in the meso-view, and shows the increase of the intensity in the macroscopic view. The presence of high confining pressure limits the rate of microcrack propagation.