Research On The Effection And Deformation Control Of Double-line Tunnel Undercrossing Existing Subway Station

During the formation of the network of network transit, it is inevitable that some new built tunnels cross the existing urban rail transit lines. The excavating of new tunnels will cause displacement of the structure and track of the existing lines, and thus influence the operation safety of the lines. How to minimize such influences, and find a safe, rational, and economic excavating method, ensuring both the building of the new tunnels and the safe operation of the existing lines, has become to be an important topic.Based on the engineering case of covered culvert tunnel of Beijing section of the South-North Water Diversion under crossing Wu Ke Song station of subway line 1, this paper studies the influence of small internal mining-method-built double-line tunnel under crossing underground station, and brings forward some conclusion as follows:1. Based on this case, this paper thoroughly studies the process of new tunnel under crossing the existing urban rail transit. According the three phases "before crossing""during crossing" "after crossing" , the basic process of under crossing and the crucial techniques are gained.2. Using monitoring data of this case, this paper carefully studies the distribution and development of the displacement of the existing station, including the settlement of the structure, the settlement of the track, the settlement of the rail and the differential settlement of deformation seam of the station. The displacement curve of the structure and track according to time and space are acquired.3. Using the software ANSYS, 3-D infinite element model are established, by which the excavating process of the covered culvert tunnel crossing the station is simulated and analyzed. The feasible of the model is confirmed by the contrasting of simulation data and the monitoring data. According to the simulation data, the main cause of the structure settlement is the excavating of the soil just under the station.4. Using the infinite model, the factors that affect station settlement, such as excavation progress, the distance of the working face of double-lines, the distance between transverse alleyway for grouting and station structure, are analyzed. The result reflects that:1) Excavation progress is of great importance to the structure settlement and vault settlement;2) Although the distance of the working face of double-line tunnels does not influence the final settlement of the existing structure, it affects the differential settlement of deformation seam greatly. Due to that, combination of bi-directional digging and per-direction can decrease the differential settlement.3) The excavating of transverse alleyway for grouting cause a small increased settlement of the station, and thus the distance between transverse alleyway for grouting and station structure is not important.4) To grout the soil under the station at a large scope is an effective way to control the settlement of the existing structure.5. Displacement distributing control principle is applied to under crossing project. The implementing process of this principle is established. Taking Wu Ke Song crossing project, the application of this method is demonstrated.