The Research On The Influence Of Approaching Construction On Shallow Buried Super-long-span Tunnel

Based on the case of Mount.Xiabei shallow buried super-long-span four line high-speed railway tunnel which was paralleled approaching by Mount.Yangtou tunnel of Taizhou Urban Railway S1 Line,this paper use the methods of theoretical analysis,numerical simulation and field measurement to makes an in-depth study on the change of shallow buried four line longspan tunnel when it was paralleled approaching by the double track railway tunnel.The purpose of this paper is to find out the law of the change of shallow buried long-span four lines highspeed railway tunnel when it was paralleled approaching by another double track railway tunnel under different working conditions.The research results are as follows:(1)When the rock level is V1,using the numerical simulation to find out the point whose safety factor is minimum on the primary support of existing long span tunnel and calculate the change rate of its circumferential principal stress when the existing long span tunnel was paralleled approaching by the double track railway tunnel.Repeat the work when the existing tunnel has different shapes,primary support of different thicknesses.And also repeat it when the subsequent tunneling has different positions,different construction method and different excavation footage.(2)700 shallow buried super long-span tunnels numerical models were modeled and calculated.Then,use the damage stage method to calculate the structural safety factor of the existing long-span tunnel after the paralleled double track railway tunnel was completed and draw safety factor influence cloud chart under various working conditions.Calculate the minimum safe clearance and affected area depends on the chart under various working conditions.(3)Through the analysis of the influence cloud chart of safety factor,the shape characteristics of the affected area under various working conditions are obtained.(4)More numerical models were modeled to calculate the minimum safe clearance when the double track tunnel paralleling the existing long span tunnel on the lower side and find the best position.(5)To make it clear that it’s necessary for the Taizhou S1 Mount.Yangtou tunnel to paralleled the existing long span tunnel on the lower side.According to the actual lower side paralleled conditions,different construction measures are proposed.Establish numerical models to calculate the minimum safe clearance under different measures,and obtain the most effective protection measures.