Displacements induced by the installation of diaphragm panels

The walls of a deep excavation in cohesionless soils below the water table have been supported by a reinforced concrete diaphragm with T-shaped panels. To improve the safety against the risk of local collapse during the panel excavation, the soil surrounding the panels has been treated by deep mixing to a depth of 6–10 m. The horizontal displacements, induced in the surrounding soil by the installation (deep mixing, slurry supported excavation, placing of the reinforcement cage, concrete casting and curing) of the diaphragm, have been measured by means of inclinometers. It is claimed that they can be a significant fraction of the total displacements induced by the excavation. A back analysis of the observed displacements shows that the deformation process is essentially elastic and can be satisfactorily modelled provided the values of the soil stiffness are properly selected