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考虑不同应力路径下的卸荷对岩石强度、变形模量等参数的影响,以铜坑矿区小扁豆状灰岩为研究对象,结合现场工程地质条件,开展了岩石卸荷力学试验,试验研究发现:卸荷岩石的破坏主要表现为脆性破坏,峰前卸围压的破坏程度大于峰后卸围压的破坏程度,峰后卸围压的破坏程度大于常规三轴的破坏程度,峰前卸围压破坏具有突发性,岩样由张性破坏过渡到张剪性破坏;在相同初始应力下,岩石卸载破坏所需应力比常规三轴压缩破坏对应的应力小,卸荷破坏时的变形比连续加载时大;衍生的卸荷裂隙随机发生,方向大体平行于X型共轭剪节理,对洞室开挖临空面定向破坏有判定性,由此现象引发片帮、冒顶等隐患需及时采取工程措施治理。
Considering the influence of unloading on the rock strength and modulus of deformation under different stress paths, taking the lentil limestone in Tongkeng mining area as the research object, combined with the on-site engineering geological conditions, the rock unloading mechanical test was carried out. The experimental study shows that : The failure of unloading rock is mainly brittle failure. The destruction of pre-peak unloading confining pressure is greater than that of post-peak unloading confining pressure. The damage of unloading confining pressure after the peak is greater than that of conventional triaxial failure. Under the same initial stress, the stress required for rock unloading failure is smaller than the stress corresponding to conventional triaxial compression failure, and the deformation ratio under unloading failure The results show that the induced unloading cracks occur randomly and the direction is parallel to the X-type conjugate shear joint. The directional damage to the caving face of the cavern is decisive. Take engineering measures to control.