The short-term stability of temporary excavations in clay deposits poses a major problem to geotechnical engineers, who must consider not only technical and economic impacts (damage to structures and substructures), but also the risk of loss of human life. The problem is taken seriously by the ministère des Transports du Québec, which produces or approves temporary excavations for the construction or maintenance of its works.
The aims of the project are to develop a safer, more precise design method for temporary excavations, to improve the department's interventions during landslides, which are essentially large natural excavations in clay, and to increase the department's knowledge of the long-term piezometric conditions of cut slopes. Such conditions must be known to facilitate evaluations of slope stability. The conditions influence a project's cost as well as user safety. The objective of the current phase of the project is to confirm that the coefficient of consolidation/swelling, based on a small-strain shear modulus and hydraulic conductivity representative of in situ conditions, controls the consolidation behaviour of clay masses.
In this phase of the project, three new cases are studied to validate the method developed in the previous phase. In order to minimize the costs of the study, the coefficient of consolidation/swelling is determined in situ by analysing the pore pressures measured during the construction of two old test embankments and the monitoring of pore pressures in a landslide study.