双连拱隧道两种工法的施工力学分析

目前，在连拱隧道施工中均不同程度地出现了围岩坍塌、已修筑的衬砌产生大面积裂缝等问题。金洞隧道位于渝怀线甘家坝与鱼泉之间。设计预留了二线隧道条件。二线位于一线右侧，进口两线间距14．09m，有分修条件：出口两线间距5．03m，设150m“燕尾”式隧道段，其中连拱隧道长42．2m。连拱隧道施工有很多种方法，在围岩条件较好时，往往采用三导洞法或两导洞法。为了比较这2种方法的施工安全性，采用有限元法对该区段隧道施工过程进行力学模拟计‘算，比较了2种不同施工方法下的洞周位移、初期支护的内力、安全系数等，得出一些有意义的结论，可作为连拱隧道施工时的参考。

STUDY ON CONSTRUCTION MECHANICS OF TWO KINDS OF CONSTRUCTION METHODS FOR DOUBLE-ARCH TUNNEL

At present, rock collapse is common existing in the construction of double-arch tunnel, and large area cracks are found in linings. Jindong tunnel is located in Yuhuan railway between Ganjiaba and Yuquan, and double lines tunnel is reserved for the second line, which lies to the right of the first line. The distance between the two lines is 14.09 m, which is wide enough to build the second one. The distance between the two lines in the tunnel exit is 5.03 m with tunnel segment of 150 m shaped coattail; and the length of the double-arch tunnel is 42.2 m. Various construction methods are available for double-arch tunnel construction. When the condition of wall rock is favorable, three-cavity or two-cavity is adopted to excavate tunnel. For the sake of the construction safety, FEM is considered to analyze the mechanics of two different construction methods, and the displacement, force of preliminary support, and safety factor are obtained. Finally, results that can provide some references to construction of double-arch tunnel are achieved.