Deformation Behavior Of Deep Metro Station Excavations With Deep Granite Residual Soil In Xiamen

With the rapid development of urban economy, urban population has increased sharply, metro rail has entered a new period of development. Due to the functional requirement of the metro subway station, the metro subway station is always located in the urban areas. The strict deformation control is required, so system study on the deformation behavior of deep metro excavation has great significance. The NO.1 metro subway station excavation in Xiamen alway has deep granite residual soil. Residual soil strength will be reduced when it contains water. Mud breakout and collapse may happen under dynamic water pressure. This paper uses a series of finite element analysis and monitor data analysis to evaluate the deformation behavior of deep metro station excavations in Xiamen. The main contents and conclusions are as follows:1. A database of 17 case histories of deep metro station excavations in Xiamen is presented. Statistical analysis on a large number of monitoring data from 13 deep metro excavations with deep residual soil is performed to study the deformation behavior and Compared to the deformation behavior of 3 metro excavations with high bed rock and a deep silt soil excavation. The mean value and upper limit of the maximum lateral displacement of retaining structure are proposed. The mean value and upper limit of the maximum ground settlement, the boundary of ground settlement, the range of impact of the ground settlement and the maximum ground settlement site are proposed. As the embedded depth ration of retaining structure is large enough, it has no matter with the deformation behavior.The system stiffness has no influence on the deformation behavior of deep metro excavation. The mean value and upper limit of vertical displacement of piles are evaluated. The embedded depth ration has no effect on vertical displacement of piles. The relation between the maximum lateral displacement and the maximum ground settlement is obtained. these deformation behaviors obtain-ed through the statistical analysis offer an approach to predict deformations of deep metro station excavations with deep residual soil in Xiamen.2. This paper uses the PLAXIS software to perform a series of finite--element analyses about the deep metro station excavations with deep residual soil in Xiamen area. Finite-element analyses is used to analyze the deformation behaviors of excavation and the change law of internal force of retaining structure. Extensive parametric studies are performed by a series of 2-D finite element analyses to investigate their degree influence on excavation induced deformations and the stress of retaining structure. The analyzed parameters include the vertical strut spacing, the prestress of inner strut, the overexcavation and the thickness of the wall. Finally, getting the general deformation behaviors of metro station excavations with deep residual soil and relationships between these deformation variables, which can provide a theoretical support for the statistical analysis of the monitoring data.3. Two metro station excavations’ data are installed in detail. Conclusions show that mean values of maximum lateral displacements of pile in SM City Square Station is close to the mean values proposed by statistical analysis of monitoring data. Mean values of maximum lateral displacements of pile in Bo Garden Station is larger than the mean values proposed by statistical analysis of monitoring data and SM City Square Station. The duration curve of vertical displacement of pile in Bo Garden Station shows that the vertical displacement is large. The ground settlements and pipeline settlement of SM City Square Station and pipeline settlement of Bo Garden Station can use the upper limit of the ground settlements defined by statistical analysis of monitoring data as their upper limit roughly. It shows that deformation behaviors get from the statistical analysis of monitoring date can be used to predict the maximum displacements around the excavation.