Anisotropic microplane constitutive model for coupling creep and damage in layered geomaterials such as gas or oil shale

摘要: Abstract An anisotropic constitutive model for coupling creep with damage of shale and other geomaterials under complex loading paths is formulated. The material described by a previously developed spherocylindrical microplane model, which can simulate not only the stress-induced incremental anisotropy but also inherent anisotropy. Like damage, must be expected to as well. responses transverse isotropy are first separately constructed compressive principal stress oriented either (i) parallel or (ii) normal bedding planes, (iii) shear along planes produced differences plane inclination angle. This leads three elementary linear models, mathematically formulated based on continuous retardation spectrum generalized Kelvin chain. These combined model. general arbitrary three-dimensional applied path. To achieve high numerical efficiency, fully explicit algorithm finite element analysis then Short-time (two-day) tests cylinders multilevel deviatoric various inclinations relative axial load conducted. simulations compared results laboratory tests. comparisons demonstrate dependence verify applicability damage. Extensions multi-year time ranges in principle possible will necessitate further calibration verification.