动载作用下圆形巷道锚杆支护结构破坏机理研究

将冲击应力波进行合理简化,建立平面P波与圆形锚固巷道相互作用简化模型。结合算例,通过分析深部围岩径向应力、巷道表面切向应力、巷道表面径向位移以及深部围岩与巷道表面径向位移差等代表性指标,确定了重点支护位置,推导了重点支护位置的锚杆受力机制并提出了相应破坏类型及判据。结果表明:迎波侧与侧向位置是重点支护位置。迎波侧锚杆总应力是静载轴应力、锚杆振动的动应力和动载下围岩变形引起的附加应力的叠加,强冲击下迎波侧支护结构的破坏类型为单次瞬间摧垮破坏,围岩受压破裂,锚杆松动失去加固作用;循环弱冲击下的破坏类型为循环累积损伤破坏,受压围岩逐渐损伤致裂,锚杆反复受压、受拉直至松动,这进一步加剧围岩的损伤破裂,当承载拱强度降低到一定值后,一次小冲击就能诱发巷道冲击破坏。侧向位置锚杆总应力是静载轴应力、动载下围岩变形引起的附加应力的叠加,锚杆始终受拉,在强冲击下可能发生拉断破坏。通过相似模拟试验,较好地验证了理论分析结果,表明理论分析结果对工程实践具有一定的指导意义。

Failure mechanism of anchored bolt supporting structure of circular roadway under dynamic load

By reasonably simplifying the stress wave, a simplified model for the reciprocity between the plane p-wave and the circular anchoring roadway is built. Based on a typical case, through analyzing such remarkable parameters as radial stress of deep surrounding rock, tangential stress of roadway surface, radial displacement of roadway surface and radial displacement difference between deep surrounding rock and roadway surface, the strategic locations of support are confirmed, the force mechanism of bolt is deduced, and the corresponding failure patterns and failure criteria are put forward. The results show that the side facing the stress wave and the lateral position are the strategic locations of support. It is found that: (1) The total stress of bolt on the side facing the stress wave is the superposition of static axial stress, dynamic stress of bolt vibration and subsidiary stress caused by the surrounding rock deformation under dynamic load. Under the strong impact, a single instantly destroyed destruction will occur, the surrounding rock is pressed to fracture and the loose bolts lose the reinforcement. Under the cyclic weak impact, the pressed surrounding rock is gradually damaged to fracture, and that the bolt is loose owing to being pressed and straightened repeatedly intensifies the fracture of the surrounding rock further. When the strength of the load-bearing arch is decreased to a certain value, a weak impact can induce the burst failure of roadway; and (2) The total stress of the bolt at the lateral position is the composition of the static axial stress and the subsidiary stress caused by the surrounding rock deformation under the dynamic load. The bolt here is being subjected to tension, so tensile failure will occur under the strong impact. The results of similar simulation experiments are consistent with the theoretical ones, indicating that the theoretical analysis can be a significant guidance for engineering practice.