NONLOCAL ELASTO-VISCOPLASTIC SLOPE FAILURE

Softening materials show very localized shear failure zones, where the width of the shear zone is of a certain limited size governed by the distribution of the grain size of granular materials. Applying a standard FE method with a softening material will show unlimited localization of the shear failure zone if the mesh size becomes smaller, which is not consistent with the finite small size as observed in reality. In Tochnog Professional this type of calculation can be performed with nonlocal visco-elasto-plasticity, in which the user can specify the finite small shear band width that should be respected; this scheme is implemented in Tochnog Professional in cooperation with the Dipartimento di Ingegneria Strutturale, Politecnico di Milano, Italy, http://www.polimi.it. Because of the very small elements needed in the shearing zone only, the user can apply an automatic mesh refinement algorithm, which automatically puts many small elements in the shear zone.

The present case refers to a slope the upper soil layer of which is subjected to weathering. The soil of the upper layer is characterized by a strain-softening behaviour. In this example, a non local elasto-viscoplastic constitutive model was used along with a mesh refinement procedure.

This method was also used to analyze a landslide of great dimensions, which occurred at Senise (Southern Italy) on 26 July 1986. The landslide was of a translational type, and the failure developed within a thin clayey silt layer interbedded by a slightly cemented sand formation. Both these soils experienced a pronounced strain-softening behaviour during laboratory tests. This calculation is courtesy of the Geotechnical Engineering Group of Dipartimento di Difesa del Suolo, Università della Calabria, Italy, see http://www.unical.it. See further "Numerical analysis of a landslide in soils with strain-softening behaviour", A. Troncone, Géotechnique, 55(8), 2005, 585-596.