浅埋偏压隧道进洞施工围岩稳定分析

针对破碎岩体浅埋偏压隧道围岩稳定性问题和进洞工法的取选,选用ABAQUS有限元软件对广西岭顶隧道分别采用三层台阶法、中隔墙法和双侧壁导坑法施工进行数值模拟研究,分析不同施工方法下围岩及支护结构的应力、应变及塑性区分布变化等情况。结果表明:由于隧道存在明显的浅埋和偏压作用,进洞适宜采用中隔墙法和双侧壁导坑法施工作业,能较好地保证隧道的稳定性。在该工程条件下,中隔墙法对拱顶和地表的沉降变形控制较好,而双侧壁导坑法对拱腰处的变形控制更佳。中隔墙法支护结构的内力和弯矩主要集中在拱顶左侧。双侧壁导坑法支护结构的内力和弯矩左右两侧对称分布,隧道拱顶正上方锚杆受力较小。进洞开挖步距不宜过大,确定每次开挖在2 m以内即可。

Stability analysis and construction mechanics of shallow buried bias tunnel openings

In view of the stability of the surrounding rock of the shallow buried unsymmetrical pressure tunnel in broken rock mass and the selection of the tunnel construction method, the ABAQUS finite element software was selected for numerical simulation study to analyze the stress, strain and plastic zone distribution changes of surrounding rock and supporting structure under different construction methods. The results showed that: due to the obvious shallow buried and biased effects of the tunnel, the use of center diaphragm method and the double-side heading method for the entry of the tunnel could better ensure the stability of the tunnel. Under the engineering conditions, center diaphragm method had better control on the settlement and deformation of the vault and the ground surface, while the double-side pilot tunnel method had better control on the deformation of the arch waist. The internal force and bending moment of the support structure of center diaphragm method were mainly concentrated on the left side of the vault. The internal forces and bending moments of the double-side pilot pit support structure were symmetrically distributed on the left and right sides, and the anchor rod directly above the tunnel vault bore less force. The excavation step should not be too large, and each excavation should be within 2 m.