A Thermodynamic Model for Rate-Dependent Geomaterials

Abstract

Geomaterials exhibit complicated rate-dependent behaviors. A deeper understanding and interpretation of these rate-dependent behaviors possess important theoretical and practical values. From the development of the rate-dependent constitutive model point of view, the paper deeply investigates the rate-dependent physical mechanisms and the mathematical models of soils. Based on the classical elasto-plastic models, traditional elasto-viscoplastic models apply viscous dissipations, similar to what has been used in fluid mechanics, for the description of rate-dependent dissipations. Traditional thermodynamic models are rate-independent. Starting from the theory of non-equilibrium thermodynamics and by introducing the matrix of migration coefficients, a thermodynamic rate-dependent model for soil is established, which is able to represent both the viscous dissipations and the non-viscous dissipations concerning rate dependency. The paper explores to which degree non-viscous dissipation, which is not familiar for the researchers of rock and soil mechanics, is able to describe the rate-dependent behaviors of soil, and carries out the constitutive modeling of one-dimensional compressional and three-dimensional shear behaviors of soil. The simulations are compared with those using elasto-viscoplastic models and the experimental results.