Large-Scale Testing for Characterisation of Cable Bolt System Behaviour: A Novel Laboratory Approach to Simulate Relative Joint Shear Sliding

This study investigates the performance of a cable bolt system under direct shearing to simulate relative rock strata under horizontal or so called “sliding”, with the primary goal of assisting in the optimisation of cable bolting practice to control roof failure in underground excavations. The multi axis substructure testing (MAST) facility was employed to develop a novel large-scale testing system. A widely used locally sourced cable bolt was selected with various testing conditions concerning the absence or presence of anchorage, grouting and cable bolt pre-tensioning, including lateral restraint to the embedment. The study shows that pre-tensioning can enhance early-stage stiffness, particularly when a lateral restraint is applied to the embedment, but its effect diminishes at larger displacements due to grout fracturing, cable bolt sandwiching, cable bolt yielding and the cracking of the reinforced concrete embedment. Grouting was essential for proper load transfer and to eliminate excessive sliding, which has been seen in the un-grouted case, where with grouted systems, failure was predominantly associated with the joint interface cracks than any bond related failures. End anchorage had limited influence, where both anchored and un-anchored systems converged in stiffness at initial cracking, although, at larger displacements, un-anchored systems seemed to be more prone to the effects of slippage. Lateral restraint mitigated cantilever-action induced rotation and un-desired localised embedment interaction, although its impact on overall stiffness was mixed. These results highlight the combined effects of pre-tensioning, grout, anchorage and lateral restraint on system behaviour, and in overall, the study establishes the versatility of the MAST facility in accommodating shear testing of cable bolt systems.