On non-coaxiality and fabric evolution of granular media in circular shear simulated by DEM

摘要

Abstract The non-coaxiality of monotonous loading for granular materials has been studied in laboratory tests and simulations using the discrete element method (DEM). However, the non-coaxiality and its relation to the fabric evolution under the stress path of circular rotational shear in the deviatoric plane remain largely unanswered. To address this issue, we report a series of true triaxial DEM simulations on initial isotropic samples to investigate the effects of stress-induced anisotropy on non-coaxiality and its fabric evolution. The mechanical behavior was captured by continuously changing the Lode angle θσdocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$theta _sigma$$end{document} under a wide range of confining pressure σcdocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$sigma _c$$end{document}, while the deviatoric stress q remains constant. In addition, the role of inter-particle friction on the non-coaxial response has been explored to elaborate on the effects of the changing of micro-structure on the macro-mechanical performance. Simulation results indicate that the non-coaxiality is the function of the stress ratio ηdocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$eta$$end{document}, confining pressure σcdocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$sigma _c$$end{document}, and inter-particle friction, which could be related to the orientation variation of contact fabric. The deviation of θdεdocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$theta _{text {d}varvec{varepsilon }}$$end{document} from the loading direction θdσdocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$theta _{text {d}varvec{sigma }}$$end{document} gradually increase as the rise of stress ratio ηdocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$eta$$end{document}, while it shows an obvious decrease trend with the increase of confining pressure σcdocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$sigma _c$$end{document} and inter-particle friction coefficient μdocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$mu$$end{document}. As for fabric evolution, it verifies the correlation between the non-coaxial response and fabric evolution in rotational shear. The directional evolution of incremental fabric θdFdocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{