Abstract: This paper presents a case history of the deep excavation safety of the excavation supporting structure for the underground fourth floor of Beiyihuan station of Hefei Metro No. 5 Line. The deformation structure responses for this excessively deep excavation are evaluated throughout the numerical analysis and the construction monitoring. The results indicate that the numerical simulated data are close to the construction monitoring data. The deformation values of the adjacent ground surface are far less than the alarming threshold value. With the increased excavation depth, the seepage area near the bottom of the diaphragm wall increases and the increased pore pressure differences between the excavated area and outside are observed. The horizontal deformation of the diaphragm wall increases with the excavation depth and the maximum lateral deformation value is observed at the middle lower portion. The maximum axial load is observed in the first level of concrete bracing and increases with the excavation depth. 

Key words: Deep Excavation with Excessively Large Depth, Deformation, Seepage, Numerical Simulation, Construction Monitoring