预切槽对钻孔内撑式破岩的定向引导机制研究

Study on the Directional Guidance Mechanism of Pre-Cutting Slot for Breaking Effect in Rock Splitting

摘要: 在非爆破岩石开挖当中，有时需要精准控制破裂面的延伸方向，以便实现破裂面的定向控制。对于钻孔内撑式破岩，室内试验表明，预制切槽可有效控制破裂面的延伸方向，是实现破裂面定向控制的有效手段之一。针对预切槽对岩石破裂面定向控制的深层次机理，采用MIDAS GTS NX对此问题进行模拟分析。模拟结果表明，当孔口设置预切槽后，在预切槽端部出现了明显的应力集中现象，且集中后的最大主应力为拉应力；在预切槽端部最先产生张拉裂缝，且张拉裂缝的方向与预切槽方向相一致；张拉裂缝形成后，裂缝的尖端也出现了与预切槽端部相同的应力集中特征，从而引导裂缝沿着预切槽的方向进一步扩展并最终形成预期的宏观破裂面。

Abstract: In non-blasting rock excavation, it sometimes needs to accurately control the extension direction of fracture surface in order to achieve expected excavation effect. The laboratory test shows that pre-cutting slot can perfectly control the extension direction of fracture surface, which is one of the effective means to obtain the expected excavation effect. The deep mechanism of how the pre- cutting slot affects directional extension of rock fracture surface is simulated with MIDAS GTS NX software. The simulation results show that the pre-cutting slot can conduce to obvious tensile stress concentration which causes tension fracture surface at the end of the slot. In addition, the direction of the tensile stress is perpendicular to the direction of the slot, so the extension direction of the fracture surface is parallel to the direction of the slot. In conclusion, the concentrated tensile stress with special direction conducted by the pre-cutting slot plays a critical role in the directional extension of the fracture surface.