Research On Deformation Characteristics Of Deep Foundation Pit Support By Reverse Engineering

The top-down method is widely used because it can make full use of the urban planning red line underground space,reduce the impact of foundation pit engineering on the surrounding environment and shorten the construction period.Chongqing area due to the special geological conditions,rarely seen by the top-down construction project.Experience in reverse construction still relatively lacking.Especially,with the reverse process of mountain building still need further research work.This paper takes chongqing guoxing tianyuan first phase of the project,4 blocks-D1#floor underground garage top-down method for foundation pit engineering as the research object.According to the western and southern section of the foundation pit,using MIDAS/GTS finite element software to establish the two-dimensional model,the control field monitoring data to test the rationality of the model,analyzes the deformation characteristics of foundation pit,the law of surface subsidence and the deformation characteristics of supporting structure in the time of excavation process.On the one hand,for the revised design and construction of the project to provide the basis for improving the project safety.On the other hand,for the future of Chongqing combined with mountain construction of the reverse process to provide experience,play a reference and predict the role.The results show that the lateral displacement of the soil around the foundation pit increases gradually with the increase of excavation depth,and decreases gradually with the increase of the distance from the edge of the foundation pit.This feature is cantilever change.The surface of the western section of the pit is in groove type,and the south section is cantilever.The lateral displacement of the retaining pile in the western section of the foundation pit is a cantilever type.With the increase of excavation depth,it is parabolic.And the southern section is cantilever type.The deformation of the beam and slab presents the characteristics of large on both sides and small in middle.The southern section of good soil,foundation pit deformation is relatively small,but no matter the west or south of foundation pit,soil deformation,ground settlement,retaining pile and concrete beam deformation are in a foundation pit control value,which shows that the foundation is stable and the support pattern is reasonable and the construction is more secure.