Experimental Investigation on Mechanical Behavior of Anchor and Shotcrete Support System Under Axial Pull-Out Action

Based on axial pull-out performance tests of anchor and shotcrete support system with three types of plates and two kinds of shotcretes (plain and steel fiber reinforced concrete) conducted by use of the multi-functional testing system. The mechanical behavior of the anchor and shotcrete support system with the different plate and shotcrete such as the pull-out performance of support system, deformation and failure properties of shotcrete was studied and analyzed. Experimental results showed that the relationship curves between elongation and drawing force has three stages, which are elastic, yielding and hardening. Different plate types have obvious influence on the tensile stiffness during the elastic stage. The steel fiber reinforced concrete spray layer can improve the yield strength of rockbolt under the coupling effect by the support system. The strain at the interface between the initial shotcrete layer and surrounding rock mass is greater than that of the external surface of the resprayed shotcrete layer, though they are equal far away from the rockbolt hole. The shotcrete strain values of steel fiber reinforced concrete is lower than that of plain concrete, and the shotcrete strain values decreases with the improvement of steel fiber content. For shotcrete strain values on the same position, the higher they are the steel fiber content, the lower their strain will be. The failure of plain shotcrete usually begins around of rockbolt hole, when the interfacial stress between the initial shotcrete layer and surround rock is higher than that in the initial shotcrete layer and resprayed shotcrete layer. The steel fiber can effectively improves the toughness, anti-cracking performance and prevent fracture of shotcrete from failure properties. The research results can provide reference for the design and construction of anchor and shotcrete support structure in underground engineering.