Research On Ground Settlement Of Double-track Undercut Tunnel Passing Through Existing Comprehensive Pipe Gallery

As China’s urban population continues to increase,the pressure on urban transportation and pipeline networks continues to increase.The construction of integrated pipe gallerys and subways needs to be further accelerated.Priority to build comprehensive pipeline corridors in areas with dense underground pipelines and rail transit will have greater social benefits.However,this also inevitably creates the problem of the tunnel passing through the upper pipe gallery.The engineering safety problem of the tunnel passing through the upper pipe gallery structure is mainly reflected in the impact on the surrounding environment.Therefore,it is of great practical significance to study the ground settlement law of the double-track tunnel passing through the existing pipe gallery.In this paper,taking the Wangfujing section of the third phase of Beijing Line 8 as the background,using numerical simulation,theoretical analysis,on-site monitoring and other methods,the stress and strain of the double-line underground tunnel through the existing pipe gallery and the formation settlement under different working conditions Conduct regular research.By comparing the settlement law of double-line tunnel excavation under the condition of non-pipe gallery structure,the influence of the pipe gallery structure and its construction process on surface settlement caused by subsequent construction is analyzed.The main conclusions are as follows:(1)Affected by the faster excavation progress of the right-line tunnel,the displacement and shear stress on the right side of the pipe gallery in the same monitoring section are greater than those on the left side.The excavation of the two-lane tunnel has certain effects on the pipe gallerys on both sides.The vertical displacement and shear stress of the pipe gallery are mainly controlled by the tunnel face closer to each other.(2)When the distance between the upper pipe gallerys is fixed and the center axis of the tunnel is inside the center axis of the pipe gallerys,the maximum settlement gradually increases as the distance between the tunnels decreases.When the distance between the lower tunnels is fixed,as the distance between the pipe gallerys gradually decreases,the width of the settlement trough generated during the two constructions also decreases accordingly.The relationship between the width of the settlement tank and the space between the pipe gallerys is linear.Compared with the influence of the change of the lower tunnel interval on the width of the settlement channel and the shape of the surface settlement channel,the change in the interval of the upper tube corridor is more significant and has a decisive effect.(3)The existence of the existing pipe corridor and its construction process can effectively reduce the ground settlement caused by the excavation of the lower tunnel.When the pipe corridor spacing is 3D,the stratum control is better.The existence of the existing pipe corridor and its construction process has a controlling effect on stratum settlement.When the vertical projection of the axis of the pipe gallery is outside the tunnel,it causes the width of the descending trough caused by the excavation of the lower tunnel to be reduced;when its horizontal projection is inside the tunnel,it will cause the width of the descending trough to be excavated by the lower tunnel.;When the horizontal projection of the pipe gallery axis coincides with the axis of the tunnel,it will not affect the width of the corresponding settling tank.(4)With the decrease of the distance between the integrated pipe gallerys,the shape of the surface settlement trough gradually evolved from “W” shape to “V” shape.Using the Peck formula to analyze the applicability of the construction settlement of the double-track underground excavation tunnel,only the settlement rules of the three monitoring sections of C = 0.68 accord with the Peck formula.When C≤0.68,under the existing structure,the surface settlement caused by the double-track tunnel passing through The existence of the existing pipe corridor and its construction process can still be predicted using the Peck formula.