Monitoring And Process Simulation Analysis For Metro Station Deep Foundation Pit Excavation With Weak Water Formation

Within the scope of extremely rich groundwater in bid201dalian subway station deep foundation pit construction, formation is very weak and easy to collapse, and with the phenomenon such as the gushing water and sand. In such geological conditions, on the phase of retaining structure construction, excavation construction and the main structure construction, the deformation law and the instability condition of the metro station deep foundation pit are more complex than the general area, it embodied that the retaining structure and the main structure of the deep foundation pit will cause adverse effects on surrounding environment during the period of construction, such as the larger surface settlement and the surrounding building collapsed. These may cause a serious hidden trouble to the construction safety. In order to solve these problems, this paper taked a deep foundation pit of Jiaotong university subway station as the research object. Based on considering the station main body structure, the initial ground stress, construction process, the physical and mechanical parameters of stratum, and many other factors, our paper use FLAC3D to simulate and research the stability of foundation pit excavation and supporting structure.At last my paper made a contrast between the simulation calculation results and the field monitoring results by Matlab to carry on safety analysis of the deep foundation pit excavation process. The main contents and conclusions are as follows:(1) My paper has expounded the part and mechanism of the deformation, the palisade structure instability form and control standards and the principle of deformation joint in the supporting structure and the soil of the deep foundation pit engineering which under weak water stratum. My paper also has pilot studied the strata consolidation settlement and briefly has introduced the main influence factors of weak water stratum deep foundation pit deformation.(2) My paper has more comprehensive instructed the deep foundation pit engineering survey and monitoring plan; the field monitoring data of different excavation periodits were analyzed and summarized in many ways,such as field monitoring methods, summarized and analyzed monitoring data of the wall top level, surface subsidence and so on, at last drawn them in different excavation period graph by Matlab,in this way, we can see the change of dynamic response. Results show that the retaining structure designed reasonably and the basic monitoring scheme is feasible.(3) In this paper, FLAC3D was used to simulate the working condition of the deep foundation pit’s excavation process and supporting process, each excavation calculation results are analyzed, the stratum deformation law,supporting axial forces and the wall deformation distribution of size are obtained, and shows that the reliability of the simulation parameters selection and calculation results are reasonable.(4) Through the simulation and measured results of contrast analysis on the deep foundation pit engineering safety stability assessment,results show that the steel support combined with the underground continuous wall can effectively maintain the balance and deformation of soil mass. And this paper predicted the stable value of the displacement of retaining structure and strut axial forces during the construction. Through the change trend of the wall horizontal displacement and supporting axial force analysising, this paper concluded that the change trend of both accord with theoretical analysis.(5) Through simulation analysis, groundwater can have a big impact on the deep foundation pit excavation.(6) From the simulated data and the displacement variation law,my paper stated the FLAC3D can simulate the excavation, supporting, precipitation and calculation of deep foundation pit.The results for future subway station deep foundation pit engineering construction provide the reference.