锚杆加固作用下圆形隧道复合岩体围岩特征曲线解析方法研究

Analytical solution for ground characteristic curve of composite rock mass reinforced by bolts in circular tunnels

传统收敛约束法中通常将锚杆作为支护结构求解独立的支护特征曲线,但是锚杆无法构成单独的支护体系,需和围岩共同作用形成承载体系。基于隧道开挖弹塑性力学解析解,考虑锚杆对围岩的加固效应,通过均匀化方法,推导了锚杆加固作用下的圆形隧道复合岩体围岩特征曲线解析解。将所推导的解析解与数值计算结果进行对比,结果表明:推导的锚杆加固作用下复合岩体围岩特征曲线解析解与FLAC^(3D)计算结果吻合较好,说明将锚杆与围岩作为复合承载体系是合理的,同时说明该方法的准确性。通过对比有无锚杆支护状态下的围岩特征曲线,说明了锚杆对围岩变形具有较好的控制作用。该解析解考虑锚杆的预应力和支护时机,为锚杆加固作用下的隧道稳定性分析提供了相对简单快速的计算方法。

In the traditional convergence-confinement method,bolts are usually considered as support structure,and the characteristic curve of supporting bolts is then derived individually. However,the support system cannot be constructed with the bolts only and must be constructed by combining the bolts with the rock mass. In this paper,the effect of bolt reinforcement on rock mass was considered. The analytical solution of the ground characteristic curve for bolted circular tunnel was derived with the homogenization method based on the theory of elasto-plasticity. The results of the analytical solution were compared with the ones from the numerical simulation. The proposed analytical solution of ground characteristic curve for bolted circular tunnel agrees well with the calculated results of FLAC^3D. It was thus concluded that it is reasonable to combine the bolts with the rock mass as the composite bearing system. The accuracy of the proposed method was verified. Comparing with ground characteristic curves of unreinforced rock and bolted rock shows that bolts have the significant effect on the deformation of rock mass. The prestress and initial supporting time of bolts were considered in the proposed analytical solution. This study provides a relatively simple and rapid method for stability analysis of bolted tunnel.