Shear behaviour of anchored jointed rock mass under different engineering conditions considering damage and joint surface morphology

Abstract

According to different geological conditions and engineering disturbance, three dimensional numerical models of anchored jointed rock mass with two kinds of boundary conditions of constant normal load (CNL) and constant normal stiffness (CNS) were constructed considering the ductility damage of rockbolt, the stiffness degradation of grouting layer and the joint surface roughness. The effects of anchorage angle, joint surface morphology, and boundary conditions on the shear performance of anchorage system were analyzed, and the failure characteristics under different working conditions were revealed. Finally, the analytical solution of shear strength of anchored system was established. Results show that the larger the anchorage angle is, the more serious the necking phenomenon of rockbolt will be. The damage degree of the bonding layer and the horizontal displacement of the bedding rock mass decrease with the increase of the joint surface roughness. The CNL condition is to instantaneously apply high normal stress, and the CNS condition is to gradually form a high normal stress environment through the superposition of increment on the basis of the initial value, which can resist greater transverse load. This is equivalent to enhancing the ductility of the rockbolt. The shear strength of the system increases with the increase of normal stress and normal stiffness. Ignoring the normal stiffness will underestimate the shear strength.