Strain-Rate Effects in Shear Highlighted by a Dynamical Systems Model

Abstract

Soil shear can be described as a dynamical system in which particles move at random shear strains into the steady-state flow structure in a process governed by simple friction. This paper studies strain-rate effects in soil shear in the context of dynamical systems soil-shear theory. The theory highlights the fact that conditions at the start of plastic deformation are strain-rate dependent and that much of the initial linear variation of stresses with strain is not attributable to the elasticity behavior of the soil but rather is the expected small-strain behavior of a nonlinear process of plastic deformation. The static coefficient of friction dominates at very small strains, after which the friction coefficient reduces to its dynamic value. Variations with strain rate in the stress-strain and void ratio–strain curves are small because of the correspondingly small dependence of the friction coefficients on strain rate.