Numerical prediction of the behavior of an excavation in residual soils

A finite element analysis was undertaken to evaluate the behavior of a deep, braced excavation in residual soils. The purpose of the excavation was to provide access to a tunnel constructed as part of the expansion of the subway system in Sao Paulo, Brazil. The stress-strain-strength behavior of the residual soils was represented by a nonassociated elasto-plastic model which was calibrated from the results of a comprehensive laboratory testing program on undisturbed soil samples. The elasto-plastic model was able to reproduce the behavior of the residual soils under different stress paths. The numerical results of the simulation include the displacements within the soil mass adjacent to the excavation and the loads in the structural components of the excavation. Although there is no development of a generalized failure mechanism, the numerical results indicate that the shear strength of the residual soils is fully mobilized in localized areas towards the bottom of the excavation.