Study On The Construction Method Controlling The Settlement Of Ground In Subway Tunnels Under The Existing Railway

Tunnels in city subway project are constructed within the rockmass.Due to the smallburied depth of the tunnels, driving of the tunnel will inevitably disturb the surroundingrock which causes convergence deformation and settlement of the ground.What is more,theworst results will affect the utility and safety.During the construction of the city subway underthe existing railway,the question which related practitioner staffs and researchers are con-cerned with is how to restrain the deformation and subsidience.On the background of the running tunnel between Yongping street station and thenorthen railway station in Qingdao metro line No.3which is under through the Jiaoji rail-way,with the aid of MIDAS/GTS,influencing factor and subsidence rules about the settlementof the ground caused by the tunnel excavation are analyzed through theoretical calcula-tion,numerical simulation and the monitoring data of the project.Effects produced bydifferentconstruction parameters on the settlement of the groundduring the tunnel excavation arecalculated and analyzed, the results are made by comparisonanalysis in order to put forword optimized the construction and design parameter and relatedinformation andtechnology on design and construction are provided for similar projects.Theconclusion is that reinforcement in advance by chemical churning piles could availably con-trol the settlement of the ground,the optimal growing circle thickness of the strtum layer is2.5m~3m; grouting range of advanced small pile in super trimbering measures is proposed to be120°; the length of the step plays the decisive role on the deformation of the surroundingrocks and the settlement of the ground,the shorter length is good for controlling thehe settle-ment of the ground,the optimal value is advised to be0.25diameter.