基于剪切滑移线理论的软岩连拱隧道喷锚支护数值模拟

Numerical simulation of shotcrete-anchor support for duplex arch tunnel in soft rock based on shear-slip line theory

软弱围岩隧道开挖卸荷形成楔形塑性区,基于RABCEWICZ L V等提出的剪切滑移线理论,计算锚杆、喷层、钢筋网、钢拱架等一次支护结构在剪切区高度上提供的支护抗力,反向施加在开挖轮廓面上;对贵阳轨道交通2#线某段连拱隧道进行数值建模,采用中导洞+台阶法施工方案,模拟其开挖支护过程,得出变形破坏效应,并与现场监测的典型断面地表沉降、边墙收敛及顶拱沉降等数据进行对比。计算结果表明:喷锚支护措施使得围岩及地表沉降、水平变形减小,有效缓解隧道开挖后的应力集中现象,重力式中隔墙在隧道开挖过程中的连拱效应明显,支护结构与围岩一起发挥了共同承载圈作用,隧道的整体稳定可以得到保证。

Excavation unloading of tunnels in soft weak surrounding rock forms a wedge-shaped plastic zone.Based on the shear-slip line theory proposed by RABCEWICZ L V et al,the supporting resistance provided by the anchor bar,shotcrete layer,steel mesh,and steel arch at the shear height was calculated and applied to the excavation outline in reverse.The numerical model of the double-arch tunnel of a section of Guiyang rail transit line 2#was built,and the construction scheme of middle guide hole-stairs method was used to simulate the excavation and support process,and the deformation and damage effect could be obtained,which were compared with the monitored data of the typical crosssection such as settlement,side wall convergence and roof arch settlement.The research results showed that the shotcrete-anchor support measures reduced the deformation of the surrounding rock,effectively relieved the stress concentration phenomenon after excavation,and the multi-arch effect of mid-partition wall was very obvious.The supporting structure and surrounding rock together layed an important role of common bearing circle,which may keep the whole tunnel stable.