Study On The Influence And Control Of Tunnel Deformation Induced By Foundation Excavation Of Above The Subway

With the rapid development of the national economy and the accelerating of the urbanization process,in order to alleviate the great pressure of ground transportation,underground rail transit get rapid development and subway plays a more and more important role in the transportation system of large and medium cities in china.Considering the fact that subway is often in the urban core area and the need of the economic development,foundation pit engineering crossing the subway is springing up constantly.So,for the excavation of the subway tunnel,how to make a reasonable prediction about the influence of excavation unloading on tunnel deformation when ensuring the safety of construction and taking effective preventive measures have great practical significance.This paper analyzed systematically the influence of excavation unloading on deformation of subway tunnel based on the background of the Xiamen Second West passage of Shigu mountain overpass through theoretical analysis,numerical simulation and other methods and summarized the deformation law of tunnel.Research results can guide the construction site,make clear the key points in the construction of foundation pit and provide scientific basis and theoretical reference for the design and construction for the similar foundation pit engineering in the future.The main contents include:1.On account of the two stage method for predicting tunnel deformation caused by unloading of foundation pit,considering the fact that the residual stress of soil mass is modified to reduce the unloading stress acting on the soil above the tunnel,the formula of tunnel longitudinal deformation caused by unloading is deduced based on the elastic foundation beam theory and then the results are verified by using the actual engineering data.The factors that affect the longitudinal deformation distribution and peak value are also studied.2.Relying on Xiamen Second West passage Shigu mountain overpass on the subway line one foundation pit engineering,the uplift deformation of the down tunnel caused by foundation pit excavation is analyzed to guide site construction accordingto numerical simulation analysis method and compared the effect of control deformation measures of foundation reinforcement,excavation scheme and others3.The influence of the factors such as the foundation pit reinforcement,the relative position of the foundation pit and the tunnel,the rigidity of the foundation pit supporting system etc.on the tunnel deformation is further studied using D numerical simulation method combined with practical engineering,4.Combined with theoretical analysis and numerical analysis results,proposed special monitoring program based on the cross section of subway excavation and make clear key points in the construction of foundation pit.