Discussion of “Three-dimensional slope stability based on stresses from a stress-deformation analysis”

Abstract

We have read this paper with interest because of our involvement in slope stability analysis of embankment dams and natural slopes. This discussion is motivated primarily from the results of example problems included in the paper for which the proposed procedure to calculate the factor of safety (FS) shows a large sensitivity to Poisson’s ratio (y). Intuitively, we were expecting to see no or very little change in computed FS results over a commonly used range of y values (say from 0.30 to 0.45). To check our intuitions, we re-analyzed each of the four example problems included in the paper using the continuum-mechanics-based procedure implemented in the Fast Lagrangian Analysis of Continua in 3 Dimensions (FLAC3D) computer program (Itasca Consulting Group 2002). Results of these analyses form the basis of comments included in this discussion. For comparison purposes, the example problems were also analyzed in plane strain mode using the continuum-mechanics-based procedure implemented in the Fast Lagrangian Analysis of Continua (FLAC) computer program (Itasca Consulting Group 2006). Size adequacy of the continuum models was verified by analyzing them via the computer program CLARA-W (O. Hungr Geotechnical Research 2010) and comparing the results with the ones included in the paper. FLAC, FLAC3D, and CLARA-W are commercially available computer programs and their adoption for re-analysis of the example problems was for convenience. Continuum-mechanics-based procedures using the elastoplastic constitutive model with a Mohr–Coulomb yield condition and a flow rule require elastic constants (two for an isotropic material) and plasticity parameters (cohesion c, angle of internal friction 4, and dilation angle j). The elastic constants used in the paper are Young’s modulus (E) and y. FLAC and FLAC3D require data for bulk modulus (K) and