Laboratory study of the behaviour of grouted cable bolts under static and dynamic axial loading

Abstract

Abstract As a typical roof-supporting system of tunnels, Cable bolts are subjected to static and dynamic loading conditions caused by ground movements and mining activities. As mining goes deeper, the chance of undetermined ground stress concentrations increases and subsequently, the probability of sudden unexpected failures such as rock bursts increases. Many studies have been carried out to simulate the axial loading condition of the tendons, especially cable bolts, under static and dynamic loading modes; however, it barely can be seen that both behaviours have been studied and compared simultaneously. From other points of view, although research has been conducted on Barrel and Wedge and load-bearing plates, these components have hardly been considered together in axial loading studies. In this laboratory study, a new pullout testing mechanism has been introduced, which is capable of implementing axial loading of cable bolts in both static and dynamic loading conditions. In addition, in a parametric study, the role of bulbs of the cable bolts as well as barrel and wedges on the load-bearing capacity of the anchors have been examined. The bond between cable bolts and grout material in the bulbed cables behaves almost 30% stronger in static and 40% stronger in dynamic tests in comparison with plain cables. In general, the required pullout energy in dynamic tests was 25-50% less than in static tests.