含双裂纹试件破坏特性力学试验及数值模拟

Numerical simulation and mechanical experiment on failure behaviour of specimens containing pre-existing two flaws

为研究含双裂纹试件力学破坏特性,为评价底板突水危险性提供理论依据.通过在真实岩石试件中预制双裂纹,基于MTS伺服控制试验机进行单轴、三轴压缩试验,并结合RFPA数值模拟,研究含双裂纹试件损伤演化和裂纹扩展过程.结果表明:1含双裂纹试件破坏模式具有明显的围压效应,随围压增加,裂纹贯通模式由拉破坏模式向剪破坏模式过渡.当围压为0时,试件在预制的两条裂纹端部分别生成外端翼裂纹和内端翼裂纹,内端翼裂纹与另一条预制裂纹搭接,导致岩桥贯通.在有围压条件下,试件出现反翼裂纹和次生共面裂纹,翼裂纹与另一条裂纹的次生共面裂纹搭接是岩桥贯通破坏的主要形式.2当岩桥倾角为135°时,原始裂纹尖端同时产生损伤,内外尖端翼裂纹同时起裂,随加载应力增加,翼裂纹不断向另一条原始裂纹方向扩展,最终扩展至另一条原始裂纹尖端,而两条外尖端翼型裂纹则扩展至试件端面,贯通整个试件后,最终导致岩石失稳破坏.

This paper investigates the mechanical damage characteristics of the real-rock specimens containing two flaws. MTS servo control testing machine is used for uniaxial and triaxial compression test, and RFPA software is also applied to research damage evolution and crack propagation process of specimens containing two flaws. The results show that：（1） failure mode of specimens containing two flaws has obvious effect of confining pressure. With the increase of confining pressure, the transition from tensile failure mode to shear failure mode is observed. When the confining pressure is 0MPa, external wing crack and internal wing crack are generated in the pre-existing crack tips. In the case of having confining pressure, the anti-wing flaws and secondary coplanar flaws are also observed. The wing crack overlapping with secondary coplanar crack of another flaws is the main failure form rock bridge. （2） when the rock bridge angle is 135°, the damage appears simultaneously, and the external wing crack and internal wing crack initiate simultaneously at the tip of the pre-existing flaws. With the increase of load stress, the two internal wing cracks extend towards another original crack, eventually extended to another original flaws tip. The two external wing flaws tip extend to the end face of the specimen, eventually lead to instability and failure of rock.