| Taking the construction of a large span shallow metro tunnel undercrossing a municipal underpass on the Chengdu Metro line as an example,using the method of theoretical analysis,three-dimensional numerical simulation caculation and field monitoring data analysis,the risk assessment and control,construction mechanical behavior,stratum and structure deformation characteristics and control of the large span shallow metro tunnel undercrossing a municipal underpass are analyzed.The completed research work and contents are as follows:(1)The Fuzzy Analytic Hierarchy Process and the risk consequence-equivalent estimation method are applied to evaluate the aggregate risk for the bored tunnel closely undercrossing the existing tunnel.The method can be used to provide reference for the aggregate risk assessment and risk control of bored tunnel closely undercrossing an existing underpass.(2)The main construction methods,excavation methods and the common ground reinforcement measures of urban subways are selected according to the scope of application and the engineering background to determine the excavation and stratum reinforcement scheme suitable for the construction of large span shallow metro tunnel undercrossing a municipal underpass.(3)The three-dimensional numerical simulation method is used to analyze the influence of the grouting reinforcement range,the excavation footage,the vertical clear distance between the new tunnel and the existing tunnel used in the construction of the tunnel on the deformation of the ground and the existing tunnel structure.And from the scope of grouting reinforcement,the length of the excavation,and the vertical clear distance between the new tunnel and the existing tunnel,suggestions are made on the control measures for the new undercut large-span tunnel underneath the existing tunnel and the deformation of the existing tunnel structure.(4)Using the three-dimensional numerical simulation method,the construction mechanical behavior and stratum and structure deformation laws during the construction of the large span shallow metro tunnel undercrossing a municipal underpass are simulated and analyzed.Combining with the field monitoring data,the construction impact and safety of the arge span shallow metro tunnel undercrossing a municipal underpass is analyzed. |
