基于复合岩体法的锚杆支护隧道收敛修正分析

基于复合岩体方法考虑锚杆与围岩的相互作用,在引入加锚效应不均匀性基础上,根据对围岩变形约束程度修正复合岩体等效计算刚度,获得了锚杆支护作用下圆形隧道收敛变形的修正解。对比既有解及数值结果验证了本文解的正确性,修正解合理地降低了既有计算方法对锚杆约束效果的过高估计。结果表明:锚杆通过提高复合围岩等效刚度降低隧道收敛变形;增加锚杆密度比增加锚杆长度对降低隧道收敛更为有效;在常规锚杆布置参数条件下,锚杆支护对隧道最终收敛的降低幅度不会超过20%,难以完全依靠系统锚杆来限制软岩隧道的收敛大变形。本文提出的修正解能合理反映锚杆对围岩收敛变形的约束作用,可为锚杆支护下隧道收敛变形的量化分析提供简洁准确的计算方法。

Modified Solution of Convergence Deformation of Bolt Supported Circular Tunnel Based on Composite Rock Mass Method

This paper investigates the interaction between bolts and surrounding rock mass and introduces the inhomogeneity of the bolts' reinforcement effect. This study is based on the homogenized composite rock mass method. The equivalent stiffness calculation method of composite rock mass is modified according to its degree of restraint on the deformation of the composite rock mass to obtain the modified solution of convergence deformation of a circular tunnel under the bolt reinforcement. The correctness of the modified solution is verified by comparing it with the existing solution and numerical analysis results. The modified solution reasonably reduces the overestimation of the bolt restraint effect by the previous composite rock stiffness calculation method. The analysis using the modified solution shows that: the bolt support reduces the tunnel convergence deformation by increasing the equivalent stiffness of the composite rock; it is more effective to reduce the tunnel convergence by increasing the bolt density than by increasing the bolt length; under the regular bolt arrangement, the reduction of the final tunnel convergence by bolts does not exceed 20%, and it is not easy to rely entirely on system bolts to limit the convergence deformation of tunnels in soft rock mass. The modified solution proposed in this paper can reasonably reflect the restraining effect of bolts on the convergence deformation of the surrounding rock, and it can provide a concise and accurate calculation method for the quantitative analysis of the tunnel convergence deformation under bolt support.