Insights into velocity-dependent shear characteristics of bolted rock joints: A comparative study of fully-grouted and energy-absorbing bolts

Abstract

In geotechnical engineering, activities such as landslides, rockfalls, blasting, and excavation often subject jointed rock masses to dynamic shear loads, impacting project stability. With continuous innovation of anchoring support technology, the appearance of energy-absorbing bolts has provided more options for rock support. This study selected fully-grouted bolts and energy-absorbing bolts, considering the roughness of natural rock joints. Indoor shear tests were conducted on bolted specimens at varying shear velocities. A comprehensive analysis was conducted on the failure morphology of joint surfaces and the fracture characteristics of bolts. Subsequently, the shear performance of both bolt types was quantitatively assessed through absorbed shear energy. At the interface between fully-grouted bolts and joint surfaces, stress concentration phenomena were observed. In contrast, energy-absorbing bolts exhibited significant necking phenomena. Under external forces, the bolt body detached from the grout, enabling it to accommodate large deformations of the rock mass and absorb energy. The results indicate that energy-absorbing bolts demonstrate better adaptability and energy absorption capacity under high-velocity shearing, while fully-grouted bolts exhibit higher peak shear stresses. Based on the experimental findings, for projects requiring consideration of dynamic shear loads and energy absorption capabilities, energy-absorbing bolts may be more suitable, providing additional safety assurance. Conversely, fully-grouted bolts may be more appropriate for applications with higher requirements for shear resistance, such as structural support under general static loads.