Choice of constitutive models in the design of excavations in coarse-grained soils supported by cantilever walls

The predictive capabilities of an elastic-perfectly plastic model with Mohr Coulomb failure criterion have been evaluated with reference to an ideal excavation in dry coarse-grained soil, supported by a cantilever retaining wall. The results, in terms of bending moments and an excavation-induced displacement field, have been compared to those given by an advanced constitutive model, i.e., the Severn-Trent sand model. This accurately reproduces the non-linear stress-strain behaviour of unbound sands, especially along monotonic stress paths. Comparison between the responses given by the two models shows that the bending moment can be acceptably predicted by the simple model, provided that it is suitably calibrated. However, only the advanced constitutive model can correctly assess the displacement field and its evolution with the excavation depth.