Systematic Analysis Method for the Unusual Large Displacement in the Excavations in Soft Soil Area

Based on a subway station excavation construction project in the soft soil area in Nanjing, an informationized monitoring scheme was conducted during the construction of excavation, and the theories of displacement prediction were introduced into the scheme for the evaluation of the horizontal displacement of the retaining structure and the settlement of the surroundings around the excavation. Based on these theories and the monitoring data, a numerical simulation based on the commercial FEM numerical analysis software, Midas GTS NX, was conducted to simulate the whole construction process. To handle the large displacement of the retaining structure observed during the construction, the actual soil layers’ status discovered by excavating, which can reflect the physical characteristics of the soil, the construction condition, and the variation trend of the monitoring data, was used in the back analysis of the factors that induced the large deformation of the retaining structure, and the analysis result was fed back to the countermeasurement organization and design such as erecting temporary steel strut. The effectiveness of these measurements in the aspect of the reduction of the deformation rate was verified, which can provide reference to the design and construction of a similar project in soft soil area.