In-situ Monitoring Study Of Deformation Laws Of Deep Foundation Pit Of Metro Station In Nanjing

Research on the deformation laws of deep foundation pit in metro station has important project value for safe construction and enclosure structure optimization design. On the basis of Pearl River subway station of Nanjing Subway Line10, the deformation laws of deep foundation pit of metro station in Nanjing are studied with the methods of theory analysis and in-situ monitoring. The main work and conclusions are as follows:(1) The main factors affecting the deformation of deep foundation pit of metro station are given:environment geological conditions, enclosure design scheme, construction scheme, foundation pit dewatering and drainage scheme.(2) The foundation pit dewatering scheme design is completed, based on the stochastic medium theory and foundation pit deformation, the prediction model of surface deformation which are caused by foundation pit dewatering and excavation is established, the model can predict the surface deformation during the foundation pit construction and the final surface deformation. The ground settlement deformation curve is given which induced by foundation pit dewatering and excavation of deep foundation pit in Pearl River east station.(3) The in-situ monitoring plan of deformation is designed, the in-situ monitoring work is completed and the deformation laws of deep foundation pit are given when the Nanjing metro station support is diaphragm retaining walls.the results show that horizontal displacement of deep soil at the bottom of Supporting structure is almost zero, the maximum horizontal displacement of foundation pit is located at about3/4of its depth. Surrounding ground sedimentation value of building envelope increases with the excavation depth increases, settlement influence scope is about3-4times of excavating depth. The distances of the maximum surrounding ground sedimentation value from foundation Surface is approximately equal to the depth of foundation pit.(4) The result shows that the trend between measured subsidence and predicted settlement curve are basically identical, the deformation prediction theory of foundation pit is reasonable.(5) Information construction is an effective mean to assure safe construction of deep foundation pit of subway station, the monitoring scheme has ensured the metro station complete smoothly and has significant economic and social benefits.