Elasto-plastic model for sand including time effect

Abstract

Abstract. Time effects on granular soils have been observed in laboratory and in situ tests but cannot be reproduced by classical elasto-plastic models. To address these concerns, existing specific modelling approaches were based on the theory of viscoplasticity formulated by Perzyna or on a viscous evanescent relationship. The present work explores an alternative following an elasto-plastic modelling framework formulated in a multi-axial structure space. The proposed elasto-plastic model is associated with a thixotropic-type framework through the use of a structure parameter, the evolution of which illustrates the competition between two effects: the time-dependent tendency of the granular system to reach its stable configurationrestructuration -and its destructuration under external perturbations. The structure parameter is linked to the existence of a stress dependent target structure towards which the current granular material structure evolves. The time scale is explicitly introduced by postulating a rate for this structure evolution. The modelling of the material behaviour has shown good similarities with the response of granular soils observed in monotonic loading, as well as during creep and variable strain rate loading experiments.

Tay creep: a multi-mechanism model for rate-dependent deformation of soils

“…As reported by Matsushita et al (1999), Pham Van Bang et al (2007, and Lade et al (2009), stepwise changes in strain rate only temporarily alter the stress-strain response before rejoining the original curve. The modeling of this transient viscous behaviour by using Tay creep model might require the inclusion of other elements such as dynamic development and loss of structure or bonding (Cazacliu & Ibraim, 2016) or decaying viscosity (Yuan & Whittle, 2018;Pham Van Bang et al, 2007). Creep following rapid stress drop Creep following stress drop is a special test to explore the time-dependent characteristics of geomaterials (Hunsche, 1988;Lade et al, 2009), where soils are allowed to creep following a rapid reduction of stresses.…”