Analyse numérique du comportement non drainé d'une argile saturée lors de l'expansion d'un cylindre creux

This study, based on the experimental analysis of Abba (1993), aims to analyse the undrained plane strain expansion and the consolidation of hollow cylindrical specimens of saturated clay. The present investigation consists in carrying out a numerical analysis on Saint-Hilaire clay assuming that this soil follows the Cam-Clay constitutive law. Various stress-controlled expansion simulations with different confining pressures were completed, which showed that the radial coefficient of consolidation hardly affects the total stress paths and the undrained shear strengths, whereas the variation of the consolidation coefficient, related directly to the permeability, influences the rate of dissipation of excess pore pressures and, thus, the effective stresses. The expansion functions and the excess of pore pressure curves were compared with the experimental results obtained by Abba (1993). This showed that the Cam-Clay method over-estimates the undrained shear strength. Silvestri (2005) presented a simple method, based on Nadai's approach (1950), to deduce the undrained shear strength from the expansion curves without any hypothesis about the soil constitutive law. This approach has been used to interpret Abba's results and has been compared to the numerical results of the present investigation. Consequently, the numerical results gave over-estimated the values of undrained shear strength.