Coupling Analysis for Rock Mass Supported with CMC or CFC Rockbolts Based on Viscoelastic Method

Abstract

Rockbolts have been widely used in rock reinforcement for high-stress conditions in mining and civil engineering. However, the interaction mechanism between the rockbolt and the rock mass is still unclear. To fully understand the coupling mechanism of a rock mass supported with rockbolts, this article studied the coupling effect and the time-dependent behavior of a rock mass supported with continuously mechanically coupled (CMC) or continuously frictionally coupled (CFC) rockbolts. The elastic solutions of the interaction model were obtained in the coupled state. In addition, viscoelastic analytical solutions were used to describe the rheological properties of the coupling model, and the solutions were acquired by setting the constitutive models of the rockbolt and rock mass to a one-dimensional Kelvin model and a three-dimensional Maxwell model based on the material properties. According to the proposed coupling model, the rock mass stress and displacement fields, and the rockbolt axial force strongly depend on the relative deformation modulus of the rock mass and rockbolt. In addition, a lower viscosity coefficient of the rockbolt or rock mass produces a larger rock mass displacement. Moreover, as the relative deformation modulus increases, the distance to the neutral point beyond the rockbolt head increases. Furthermore, the position of the neutral point is independent of time.