Prise en compte du mécanisme des déformations plastiques dans les calculs des excavations profondes

The need to increase the density of urban areas in congested cities leads to the execution of underground infrastructure such as deep excavations. The ground movements induced by their construction may cause damages on the existing buildings. The existing constitutive models used for the simulation of deep excavations with the finite element method do not always lead to results consistent with field measurements. The numerical simulations tend to show a heave of the ground just behind the retaining wall while measurements show settlements. These differences can be explained by the choice of a constitutive model unsuitable to the description of the ground unloading. This paper proposes an elastoplastic constitutive model which makes it possible to calculate settlements just behind the retaining wall. The key feature of the model is the combination of a specific hardening mechanism with a flow rule leading to a contractive behaviour. A numerical analysis of a well-documented anchored wall in Berlin sand is presented.