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紫之隧道是处在Ⅴ、Ⅵ级软弱围岩中的浅埋暗挖小间距双线隧道,采用交叉中隔壁台阶法分部开挖。开挖前实施管棚和小导管超前支护,并对开挖面进行注浆加固。开挖后采用喷混、钢筋网、锚杆和钢拱架形成初期支护。本文对后建隧道掌子面的滞后距离进行数值分析研究,发现双线隧道施工导致的地表沉降要大于单线隧道,且沉降槽偏向于先建隧道;增大后建隧道滞后距离可以减小先建隧道的地表和拱顶沉降,而后建隧道相关沉降则略有增加;增大后建隧道滞后距离可以减小先建隧道的洞内收敛值,对于后建隧道的洞内收敛值无明显影响。
Purple tunnel is located in Ⅴ, Ⅵ level of weak rock in the shallow buried double tunnel excavation small spacing, the use of cross-septal method of sub-Division excavation. Excavation before the implementation of pipe shed and small catheter advance support, and excavation surface grouting reinforcement. After excavation using spray mixing, steel mesh, anchor and steel arch to form the initial support. In this paper, the numerical analysis of the lag distance of the back face of the tunnel is carried out. It is found that the surface settlement caused by the construction of the double-track tunnel is larger than that of the single-lane tunnel and the settlement trench is inclined to build the tunnel first. The settlement of the surface and vault of the tunnel was built, and then the related settlement of the tunnel was slightly increased. Increasing the lag distance of the tunnel after the tunnel construction reduced the convergence value of the tunnel before the tunnel construction, and had no obvious effect on the convergence value of the tunnel after the tunnel was built .