Study On The Influence In Approaching Construction Of Underground Structure Based On Cover And Excavation Top-down Method

With the rapid development of urbanization in our country, some problems aregetting serious such as urban land resources tension and traffic jam, the developmentof underground space can not only solve these problems effectively, but also play apositive role for the sustainable development of urban economy. At present, manydomestic and foreign big cities have seen the development and utilization of urbanunderground space as key construction projects. However, with the large-scaleconstruction of underground engineering, the phenomenon of the new undergroundengineering near the existing underground structure will be meet inevitably. Theconstruction of the new underground engineering not only disturbances thesurrounding rock and soil that lead to redistribution and adjustment of stress, but alsoeffects the existing underground structure such as the changes of deformation andinternal force, etc.Based on the construction of the underground commercial street near theexisting metro tunnel structure in a city, this paper analyses the influence and changelaws caused by the approaching construction process of cover and excavationtop-down method through numerical simulation analysis by finite element softwareMIDAS/GTS. During the research process, this paper discusses the approachingconstruction processes which mean the first floor underground up-crosses the existingmetro tunnel structure and the second floor underground near-crosses the existingmetro tunnel structure respectively. The influenced range is divided according to thecloud picture of displacement caused by the approaching construction, and thechanges of each influenced range are discussed for example the shear stress of thesoil; and this paper researches displacement and internal force changes of the existingmetro tunnel structure during the approaching construction processes; the situation ofinternal force change of the first floor underground structure caused by theconstruction process of the second floor underground structure is also discussed.Through the analysis of the results of numerical simulation, this papersummarizes the situation of changes caused by the new underground engineeringapproaching construction near the existing metro tunnel structure, and draws theconclusions that the approaching construction is safe and secure. The series ofresearch can provide reference for similar approaching construction, and theprospects for the further research are also presented.