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目前大多数隧道采用的是爆破掘进,炸药爆炸后的冲击应力会对隧道围岩造成不同程度的损伤。隧道围岩的损伤积累会降低围岩强度进而会影响岩体稳定性。岩石的破坏过程在微观上是内部缺陷微裂隙发展、传播、贯通,但岩石的内部微裂隙损伤难于直观观测。笔者通过室内岩石三轴压缩破坏试验和声发射特征试验所获得岩石加载过程的特征应力点判断岩石内部微裂隙发展阶段。特征应力点有裂隙初始应力—原岩损伤强度、爆破应力—凯塞点强度、裂隙贯通应力(长期强度)—原岩强度、抗压峰值强度。基于对围岩破坏过程的特征应力点的研究,提出了围岩爆破前后的损伤比例公式,量化了隧道爆破后围岩相对于原岩的损伤程度。
At present, most tunnels are used for blasting tunneling. The impact stress after explosive explosions will cause different degrees of damage to the surrounding rock of the tunnel. The damage accumulation of the tunnel surrounding rock will reduce the surrounding rock strength and thus the stability of the rock mass. The process of rock destruction is microscopic microcracks internal development, propagation, penetration, but the internal micro-cracks in the rock difficult to visual observation. The authors determine the stages of the development of microcracks inside the rock through the characteristic stress points of the rock loading process obtained from triaxial compression failure test and acoustic emission characteristic test of indoor rock. Characteristic stress points have initial stress of fracture - damage strength of original rock, blasting stress - Kaiser point stress, crack penetration stress (long-term strength) - original rock strength and compressive peak strength. Based on the study of the characteristic stress points in the process of surrounding rock destruction, the damage proportion formula of surrounding rock before and after blasting is proposed, and the damage degree of surrounding rock relative to original rock after tunnel blasting is quantified.