Study On Effect Of Kunming Rail Transit Line 4 Undercrossing On Existing Line 2 And Deformation Control Technology

With the rapid growth of urban economy and the continuous expansion of urban population,the construction of rail transit has become one of the main means to relieve the traffic pressure in the process of urban development and construction.In recent years,more and more urban rail transit has entered the peak period of construction,and the problem of crossing multiple lines is inevitable.And how to ensure the operation safety of the existing tunnel when the new tunnel crosses the existing line has become the key problem to be solved.This paper is based on Kunming Rail Transit Line 4 overlapping the existing Line2 as the engineering support.And on the basis of the engineering geological condition of the project location,the influence of the proposed tunnel construction on the segment displacement of the existing Line 2 tunnel is studied by numerical simulation when different factors change,including jacking force,grouting pressure,construction sequence,reinforcement range,etc.Combined with the field monitoring data,the existing structure and surface deformation law of the double-line shield tunneling overlapping the existing tunnel are analyzed.Suggestions on key construction measures for crossing construction of the project are put forward.Through the numerical simulation results,it is concluded that under the premise of comprehensive consideration of safety and economy,when the construction sequence is first down and then up,the jacking force is 390 kPa,the grouting pressure is 350 kPa,and the reinforcement scope is 3.5m,a relatively good deformation control effect can be achieved.The automatic monitoring and measurement system can accurately and quickly feedback the monitoring data of the existing tunnel,and efficiently guide the construction.The field monitoring data show that reasonable shield construction measures can effectively control the deformation of the existing tunnel and ensure the safety of the existing line operation.The new double-track tunnel overlapping the existing tunnel has a certain superposition effect on the deformation of the surrounding soil and the existing structure.The deformation law shows that the existing tunnel heave first and then sinks with the shield tunneling,and the settlement changes mostly occur after the shield tail leaves the existing tunnel.