3D Displacement Field Around a Deep Excavation

The movements around a deep excavation in urban environment is one of the main design issue to be addressed. Various tools are available and they are categorized in different approaches. The first one, the semi-empirical approach, is based on empirical relations between displacements and simple geometrical parameters such as the depth of the excavation H_e, or the depth of the bedrock H_b. Generally these methods allow for separate predictions of transversal and longitudinal settlement trough. A second one, the numerical approach, is based on the prediction of the green field subsidence trough by means of FEM or DFM. In this case a 2D simulation of the shaft excavation under plane strain assumption is a typical and nearly routinely design step. The large computational resources available have recently pushed forward the frontier of the simulation capabilities allowing a relatively easy access to large 3D numerical models. In the paper FEM analyses of a deep excavation in an urban environment are presented. The subsoil layering is typical of the Napoli area (Italy) and computed 3D settlement troughs are exposed. The influence of typical buildings in the subsidence area is evaluated and discussed on the basis of the computed results and of fitting functions combining longitudinal and transversal settlement trough.