Abstract
Abstract The effect of fabric anisotropy on strength has not been considered in most strength criterions for granular material. Some criterions can describe the variation of material strength with stress-induced anisotropy, but micro-mechanism and physical meanings are undefined. Some criterions consider the effect of fabric anisotropy, but the evolution of fabric is ignored during loading by assuming a constant fabric tensor. Based on strength mechanical characteristics of granular material, in this paper, the relationship between macro stress and micro contact force of granular material is derived by micromechanics. Then, the concept of true stress tensor is proposed. An anisotropic strength criterion of granular material considering fabric evolution is established and its applicability is validated by comparing with test results for different granular materials. The analysis results indicate that the proposed anisotropic criterion can be utilized to describe the strength feature of anisotropic granular materials, which gives a way for the cause analysis of the strength of granular materials from the perspective of Microscopic mechanism.
Highlights
Strength problem is always a focus in granular mechanics
M-C criterion does not take into account the effect of middle principal stress and the deviatoric shape is hexagon; M-N strength criterion predicts the same strength with M-C criterion for both triaxial compression (TC) and triaxial extension (TE)condition, the effect of middle principal stress is taken into account; While the strength of L-D criterion under TE is higher than that of the other two
The relationship between macroscopic stress and microscopic contact force of granular material is derived by micromechanical method at first and the concept of true stress is proposed
Summary
Strength problem is always a focus in granular mechanics. Numerous strength criteria for granular material have been developed so far, such as the Mohr-Coulomb (M-C) strength criterion, Matsuoka-Nakai (M-N) criterion (Matsuoka and Nakai, 1974), Lade-Duncan (L-D) criterion (Lade and Duncan, 1975) and so on. There are various cross-isotropic strength criteria for geomaterials to characterize the stress-strain-strength anisotropy by introducing variables that include the information of material fabric and external loading into classical isotropic strength criteria. Many anisotropic failure criteria for granular medium was established by combining fabric and stress tensor A novel anisotropic strength criterion considering fabric evolution is proposed for granular medium by introducing the fabric evolution formula into the true stress tensor. The applicability of the proposed strength criterion was validated by comparing with experimental results for different granular materials
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