| As the construction density of the urban core area increases,the construction of underground rail transit and the development of underground space have become the main directions of urban construction.A large number of deep foundation pit projects adjacent to existing subway tunnels have appeared.Excavation of deep foundation pits adjacent subway tunnels have adverse impact on the safety of the tunnels.However,recent researches in this area are inadequate.This research first analyzed 10 cases of foundation pit projects adjacent to subway tunnels in Shanghai area,and on this basis,summarizes the influencing factors and laws of the deformation of adjacent tunnels caused by deep foundation pit excavation.Then,the current research carried out theoretical research on the safety assessment of underground engineering construction.Based on the analysis of construction safety assessment methods,the factors that affect the safety of subway tunnels such as construction technology,environment,personnel,equipment and management were analyzed.Aiming at the two working conditions of the subway tunnel located at the side of the deep foundation pit and the subway tunnel located at the bottom of the deep foundation pit,combined with the actual engineering case,two finite element models were established to analyze the deformation of the tunnels during the construction process and Safety judgments were given by comparing with the safety judgment standards.Also,the project recommendations combined with actual working conditions were given.The results of this research are conducive to improving the construction safety management level of deep foundation pits adjacent to existing subway tunnels,providing new theoretical methods and analysis case references for the safety assessment of such engineering projects,and can guide construction technicians to carry out tunnels deformation analysis and safety assessment,which have a certain value in technology application. |
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