极小净距交叠隧道二衬支护控制研究

Research on control technology of secondary lining in overlapping tunnels with super-small spacing

青岛地铁2号线枣李区间隧道下穿3号线泉李区间隧道,交叠段隧道围岩以强风化花岗岩为主,岩体破碎。为保证地铁正常铺轨及长期安全运营,开展了二衬支护控制研究。通过理论分析确定出二衬最佳支护时段,并提出三种二衬支护方案,利用数值模型分析各方案对交叠段围岩拱顶沉降、二衬结构变形及应力、塑性区形态特征的影响。最终提出交叠隧道二衬支护的最优方案为:在交叠区影响范围外,3号线在隧道初支变形趋于稳定后施作二衬;在交叠区段,2号线开挖完成且3号线二次变形稳定后对其施作二衬。模拟结果验证了理论分析的正确性,为交叠隧道二衬支护控制提供了技术指导。

The tunnel between Zaoshan station and Licun station of Qingdao metro line 2 under-crosses Quanli interval tunnel of line 3 and surrounding rock of overlapping tunnel is mainly composed of strongly weathered granite,rock mass of which are broken.In order to ensure the normal track layout and long-term safe operation of subway,secondary lining support control was studied.The optimal supporting time of secondary lining was identified by theoretical analysis,three secondary lining support schemes were put forward,and the influence of each scheme on vault settlement of overlapping surrounding rock,structure deformation and stress of secondary lining and morphological characteristics of plastic zone was analyzed by numerical model.The optimal scheme of overlapping tunnel secondary lining support is as follows：the secondary lining of line 3 should be constructed after primary support deformation tends to be stable outside the area of the overlapping,and the secondary lining of line 3 should be constructed after line 2 excavation finishes and two-stage deformation of line 3 is basically stable in overlapping area.Simulation results demonstrated the validity of the theoretical analysis,which would provide a technical guidance for secondary lining support control of overlapping tunnel.