Study on the Influence of Pit Excavation on the Stability of Underground Openings Using Different Models

Simplified plane strain model and 3-D model were used to research the influence of pit excavation on the stability of underground openings using the finite element method (FEM). Conclusion from the 3-D FEM study is that the central region of the pit will have a large springback deformation and the openings will also float up at the same time because of large ranges of pit excavation. When using the simplified two-dimensional plane strain model for the analysis of this problem, the size of the excavation region leads directly to two completely inconsistent results. If the excavation region was wider than the openings the springback deformation would be obtained, while the settlement would be obtained if the opening was wider than the excavation region. Therefore the two-dimensional plane strain model is not proper for the analysis of the stability of the openings under this condition.