Study On The Effect Of Asymmetric Foundation Pit Excavation And The Influence Of Its Excavation On Underground Metro Tunnel

With the development of infrastructure in China,the major cities often have the limitations of topography and site conditions,and the comprehensive problems of asymmetric bias foundation pit and foundation pit crossing existing metro tunnels are becoming more and more prominent.Most of these projects are located in the central area of the city,the surrounding environment is complex,improper treatment will lead to safety problem of the foundation pit engineering and the existing tunnels.This paper relies on the first trans-metro asymmetric deep foundation pit project in Xiamen which is the Second West Corridor of Xiamen to cross the AMTR Line 1.On the basis of reading a large number of literatures,this paper systematically studies the excavation effect of unsymmetrical bias foundation pit and the influence of foundation pit excavation on the underground subway tunnel through the method of engineering characteristic analysis,field measurement and numerical simulation.The following are the pivotal research contents and conclusions:(1)Reading the relevant literatures at domestic and abroad,summing up the previous research results,pointing out the existing problems and deficiencies.The complex engineering characteristics and special geology of the background engineering are analyzed comprehensively,summed up the key points and difficulties of background engineering.(2)By using the method of field measurement,making detailed and reasonable measurement scheme,obtaining the datas of critical section,and analyzing the field measured data.The deformation and mechanics mechanism and influencing factors of unsymmetrical Foundation pit and down tunnel are analyzed respectively.This paper sums up the deformation and mechanical characteristics of the structure of the composite geological asymmetric bias foundation pit and the underground tunnel.(3)A three-dimensional numerical model is established by using FLAC3 D software to simulate the influence of the cross foundation excavation process on the structure of the foundation pit and the existing tunnel in the heterogeneous formation geology,and the simulation results are compared with the measured results to verify the rationality of the model and the accuracy of the measured results.The relationship between the deformation of the underground tunnel and the displacement of the deep soil is obtained.(4)Summarizing the research results of measurement and numerical simulation,the deformation characters and mechanical characteristics of the asymmetric deep foundation pit and metro tunnel in Xiamen area with soil-rock complex geology are obtained,and the results of this study not only guide the smooth and safe construction of the project,but also provide the scientific basis and engineering practice for the construction?design and protection of similar projects in Xiamen area and even in China.