Finite Element Simulation of Deep Excavation Failures

Deep excavations play an increasingly greater role in the development of urban transportation infrastructure facilities such as subway systems and underground space. This paper presents the results of finite element simulations of two deep excavations in soft cohesive soils involving collapse. An enhanced bounding surface soil model characterizes the cohesive soils. The model is anisotropic and is formulated with a non-associative flow rule, but can be degenerated to an isotropic model with associative flow. The results of the excavation simulations give insight into the ground response in terms of lateral wall deflections, ground surface settlements, wall bending moments, and strut force developments. Anisotropic and isotropic versions of model showed differences in simulated results. The insignificant difference in results between the associative and non-associative versions of enhanced bounding surface model is illustrated, but it is expected that, in general, the use of non-associative flow rule will provide a more realistic simulation.