Study On Deformation Control Of Deep Foundation Pit Excavation Of Subway Station

Human’s living space on original surface decreases rapidly after 21st century. Underground space becomes the focus of development now. The deep foundation pit engineering, basis of underground space, has been greatly developed, but it is still in the stage of semi theoretical and semi empirical. Therefore, the effective solution to the problem of deep foundation pit excavation and support in hostile environment become the focus and difficulty of the development of underground space. The advance predictions for changes of displacement field and stress field of soil are mostly completed by establishing three-dimensional finite element model in the deep foundation pit engineering. The parameters of soil obtained from the laboratory tests were affected by various factors which led to large deviation between numerical calculation and field measured results. It is difficult to forecast the changes of foundation pit accurately, and increase the possibility of occurrence of safety accidents. In this paper, a three-dimensional finite element model of deep foundation pit excavation was established using MIDAS/GTS software. Parameters of soil were modified by the method of numerical calculation and information feedback based on the field measured data so that it closed to the state of soil actually. Through the analysis of numerical calculation results, the basic discipline of force and deformation of foundation pit support system as well as the displacement of inner and outer soil was obtained, and the influence on the settlement of adjacent buildings was summarized. In addition, the factors of affecting the deformation of foundation pit were analyzed by changing the parameters of the model to take effective measures to control the deformation of foundation pit. The results, compared the calculated value with the measured value, showed that the changes of the displacement and stress field of soil in the foundation pit meet the requirements of design and demonstrated, the supporting structure is effective, and the excavation scheme is feasible. The numerical analysis result is in close agreement with the measured result which proved the accuracy for forecasting the change of foundation pit by combining numerical calculation with information feedback. These results can provide reference for the design and construction of similar projects in the future.