Effect of Consolidation on the Behaviour of Excavations in Fine-grained Soils

This study deals with the detrimental effects of consolidation on the behaviour of excavations carried out in fine-grained soils. With the aim of reproducing the main aspects of the mechanical behaviour of medium-soft clays, an advanced constitutive model was adopted, which is based on bounding surface plasticity and can take into account the damage to the soil microstructure induced by plastic strains. In a first stage of the work, this constitutive model was implemented into a finite element program, and its response was studied through a series of single-element tests, evidencing the effect of the different soil parameters and initial conditions. In the present paper, the constitutive model was used to simulate the behaviour of an idealised excavation, studying the effect of the progressive dissipation of the excess pore water pressures generated during the excavation stages. It was found that, under certain conditions, the initial degree of structure can be progressively lost during consolidation. This detrimental effect produces significant deformation increments and in some cases can drive the system to collapse.