Effects of the excavation procedure on the stability of diaphragm wall panels

The stability of panels during construction must be always considered in the design of diaphragm walls. The classical 2D methods to evaluate the maximum depth of excavation of a trench with or without slurry are too conservative for panels, because of the unrealistic geometrical simplification. Trying to back analyze a failure observed in Napoli during the excavation of a panel in a weakly cemented soil without slurry support, it was found that the position of the operationg machine on the edge of the panel likely played a role in the mechanism. Therefore, 2D and 3D FEM parametric numerical analysis have been carried out, to consider some relevant aspects that are generally neglected at the design stage, such as the real 3D geometry of the panels and the position of the operating machine. By comparing the FEM results with available 2D and 3D analytical solutions, it is found that the machine can play both a positive and a negative role on the stability of the panel, depending on its position.