管棚预支护条件下隧道开挖面三维稳定性分析

3D Stability Analysis of Tunnel Excavation Surface with Pipe Roof Reinforcement

为了研究管棚预支护对隧道开挖面稳定性的影响,从塑性极限分析机动学方法出发,利用土的强度折减系数概念,建立了管棚预支护条件下隧道开挖面三维稳定性分析模型,由此确定开挖面稳定系数及其相应的潜在破坏模式。结合实际工程,采用该方法计算得到的开挖面极限支护压力与有限元强度折减法的计算结果吻合较好,验证了本文方法的合理性。进而研究了隧道埋深、隧道洞径及围岩条件对开挖面稳定性的影响,分析了上述因素与开挖面极限支护压力及稳定系数的关系。对有无管棚预支护隧道开挖面稳定性分析表明:在软弱地层、大跨洞径等条件下,管棚预支护能有效提高开挖面稳定性。

In order to study the influence of pipe roof reinforcement on tunnel excavation surface stability, based on the kinematic method of limit analysis and the soil strength reduction coefficient, the 3D stability analysis model of tunnel excavation surface with pipe roof reinforcement was established, which was employed to define the safety factor and its corresponding potential failure mode of a given tunnel. For a certain tunnel excavation, the ultimate support pressure of tunnel excavation surface computed by the proposed approach is consistent with the results given by strength reduction FEM, which verified the reasonability of the method. Then, the proposed approach was also employed to study how the tunnel cover depth, tunnel diameter and surrounding rock affect the surface stability, ultimate support pressure and safety factor of tunnel excavation surface. The analytical results of tunnel excavation surface stability with/without pipe roof reinforcement reveal that in soft weak stratum and large span excavation conditions, the pipe roof reinforcement can increase excavation surface stability effectively.