Analysis on safety margin and damage model for excavation support structure in very deep pit

The size of a very deep pit is about 69 x 50 x 50m. The excavation support structure in this pit is continuous concrete wall with internal support structure, and the continuous wall is embedded into bedrocks. In order to know the safety margin and the damage process of this pit, 3-D nonlinear finite element analysis with excavation simulation is carried out. The self-weight of soil in the finite element model is increased hypothetically until the support structure is destroyed. Comparing the assumed self-weight of soil to the real one, the safety margin of the pit can be obtained. The numerical results show that all the failure of the pit begins with the collapse of the internal supports and the failure models are different in various excavation depths.