The aim of the double pipe axial tests was to determine the axial behavior of different test bolts under loading and determine the mechanical applicability of corrosion protected cable bolts for long-term reinforcement demands. The bolt types tested were epoxy coated steel strand, galvanized steel strand, plain steel strand, galvanized rebar and bulbed strand. The new double pipe test system for axial testing oflong test bolts is presented. A total of24 axial tests were performed successfully. The results gave a very clear impression of the behavior of each bolt type under axial loading. The corrosion protection treatment improved the bond strength resulting in a higher breaking load and higher stiffness in the behavior of the bolt. The epoxy coated steel strand and the galvanized steel strand had almost equal behavior in tests despite differing corrosion protection. The results obtained were found positive considering cable bolts in long-term reinforcement.
Cable bolting has been used successfully in reinforcing the stopes in mines in Finland since 1971. The most used cable bolt material has been seven-wire steel strand. The interest in the expanded use of cable bolting in civil rock engineering is increasing due to the many benefits of-the-cable bolting method and the material properties of steel strand. However, the uncertainty of the sensitivity to corrosion has been the main problem to be resolved before cable bolts can be accepted for use in long-term reinforcement. The difference in the mechanical behavior between a conventional rock bolt, like rebar, and a cable bolt is very important to determine as well.
