邻近爆破下不同形状巷道围岩裂纹扩展规律

为了解巷道断面形状对爆炸载荷下邻近巷道围岩裂纹扩展规律的影响,采用模型试验和扩展有限元(XFEM)方法展开详细研究。试验研究表明:爆炸载荷下,当原有裂纹扩展通过邻近巷道围岩原有裂纹尖端影响区、应力波传播过程产生的环向拉伸区和自由面反射波影响区时,扩展方向有所不同;巷道断面形状主要影响原有裂纹后期扩展方向,巷道断面形状不同,自由面反射拉伸波的拉伸应力方向不同;由于拉伸应力方向一般垂直于自由面,直墙拱形巷道和圆形巷道围岩中原有裂纹扩展后期偏转向弧形自由面切向方向,近似"层裂"现象扩展;矩形巷道围岩原有裂纹扩展方向与直墙反射波拉伸应力作用方向平行,裂纹扩展不受影响,仍沿近似水平方向与自由面贯穿。

Propagation Law of Cracks in Surrounding Rock of Different Shape Tunnels Under Adjacent Blasting

To understand the effect of the tunnel section shape on the crack propagation law of surrounding rock in adjacent tunnel under blast loading, detailed research is carried out by model test and extended finite element(XFEM). The experimental study shows that under the blast loading, when the original crack grows through the original crack tip zone of the adjacent tunnel surrounding rock, the circumferential tensile zone resulting from propagating stress wave and the reflection stretch zone under the influence of the adjacent free surface of the tunnel, the growth directions have a great difference. The section shape of the tunnel mainly affects the extension direction of the original crack at the later stages. When the section shape of tunnel is different, the direction of the tensile stress of the free-face reflection tensile wave is also different. Since the direction of the reflection tensile stress is generally perpendicular to the free surface, the original cracks in the surrounding rock of the straight wall archway tunnel and the circular tunnel grow along tangential to the curved free surface, and the approximate "layer crack"phenomenon appears.However, the original crack propagation direction of the surrounding rock of the rectangular tunnel is parallel to the direction of the tensile stress of the vertical plane reflection wave, and the crack propagation is not affected, and it is still penetrated into the free surface along the approximate horizontal direction.