Shear mechanical properties and debonding failure mechanisms of bolt-resin-rock anchoring system with anisotropic interfaces

Abstract

This study investigates the shear mechanical responses and debonding failure mechanisms of anchoring systems comprising three anisotropic media and two anisotropic interfaces under controlled boundary conditions of constant normal load (F_s), constant normal stiffness (K), and shear rate (v). A systematic analysis of shear mechanical properties, the evolution of maximum principal strain field, and damage characteristics along shear failure surface is presented. Results from direct shear tests demonstrate that initial shear slip diminishes with increasing F_s and K, attributed to the normal constraint strengthening effect, while an increase in v enhances initial shear slip due to attenuated deformation coordination and stress transfer. As F_s increases from 7.5 to 120 kN, K from 0 to 12 MPa/mm, and v from 0.1 to 2 mm/min, the peak shear load increases by 210.32% and 80.16% with rising F_s and K, respectively, while decreases by 38.57% with increasing v. Correspondingly, the shear modulus exhibits, respectively, a 135.29% and 177.06% increase with rising F_s and K, and a 37.03% decrease with larger v. Initial shear dilation is identified as marking the formation of shear failure surface along anisotropic interfaces, resulting from the combined shear actions at the resin-bolt interface, where resin undergoes shear by bolt surface protrusions, and the resin-rock interface, where mutual shear occurs between resin and rock. With increasing F_s and K and decreasing v, the location of the shear failure surface shifts from the resin-rock interface to the resin-bolt interface, accompanied by a transition in failure mode from tensile rupture of resin to shear off at the resin surface.

Keywords

anchoring system / anisotropic interfaces / shear mechanical properties / strain field evolution / debonding failure

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Central South University