Study On Deformation And Environmental Effect Of Deep Foundation Pit Excavation On Saturated Soft Soil Layer

A large number of deep foundation pit engineering springs up in the wave of urbanunderground space development and the construction of high-rise building. With thedevelopment of society, the scale and depth of deep foundation pit engineering increasesgradually, the support structure and excavation method is also more and more complex.Inevitably, the deformation of retaining structure and soil around foundation pitbe caused by the excavation of the deep foundation pit, how to control the deformationof foundation pit is one of the key issues in the field of underground works. At the sametime, the foundation pit engineering is usually applied in the city, the environmentalimpact of foundation pit excavation and environmental protection is an important issuewhich needs to be studied and explored by technical personnel in the foundation pitengineering.Based on the practice of the foundation pit engineering in Nanjing Xishui Guan,the deformation of foundation pit during excavation and the environmental effect isstudied in this paper. The main research contents are as follows:(1) Analysis of deformation of foundation pit during excavation. Through studyingthe deformation mechanism of foundation pit, MIDAS/GTS finite element software isused for dynamic simulation of the whole process of the deep excavation, thedeformation of the structure; the environmental impact and the stress characteristic ofinternal supporting system were predicted. It was concluded that to control overloadreasonably around the foundation is of important significance to keep the stability ofbracing structure and control the deformation of the retaining structure of thefoundation.(2) The control of the deformation of foundation pit and accident analysis. Throughmaking full use of the principle of time space effect, the measures to control thedeformation of foundation pit during excavation were put forward. The optimizationscheme of the excavation of the same foundation is simulated by using the finiteelement software GTS. Compared with the original scheme, the effect of deformationcontrol was obtained and applied to the construction where environment needed to beprotected specially. Combining with the design, construction and numerical calculationresults, foundation engineering accident in Xishui Guan was analyzed thoroughly. Thereasons of the accident were found out, and effective remedial measures were taken.The results can be a useful reference for similar projects in the future. (3) The research on environmental protection and monitoring of foundation pit.Combining with Engineering Practice, environmental problems caused by foundationpit engineering were summarized, the causes of environmental problems were analyzedand the corresponding environmental protection measures were put forward.Through the monitoring of open excavated deep foundation pit of Shuixi gatetunnel, a great many monitoring data was obtained. After analysis of the data, theuniversal law of stress and deformation of the pit structure and environment wereobtained in order to guarantee the safety of the excavation.