Introduction of a thermodynamically hyperelastic model for peat

Abstract

Peat is a complex geomaterial having extremely high water content, low shear strength and undergoes large deformations under loading. Based on the volume fraction concept, this paper presents a basic hyperelastic biphasic material model for saturated amorphous (fully decomposed) peat. It has been a common practice to study hydraulic (volumetric) and mechanical (deviatoric) processes separately, although this division is artificial and disregards the complete stress-deformation response of a soil. The present study presents a hyperelastic model implemented within a thermodynamically consistent approach of coupled hydraulic and mechanical processes, thereby eliminating associated artificial separation errors. This phenomenological material model has been implemented inABAQUS using the user subroutine UMAT. In order to adequately capture the complex geomechanical behaviour of peat, future work should include the addition of viscoelasticity, creep, structural anisotropy and (when extending to larger strains) plasticity to the basic hyperelastic model presented.