Investigation of the behaviour of rock bolts and tendons in shear under static and dynamic loading conditions

The instability of the rock surrounding underground excavations and engineering tunnels is an ever-present threat to both the safety of human life and equipment. To eliminate or minimise these threats, it is necessary to understand the root cause of the instability of the rock mass in underground structures. Two groups of reinforcements are adopted to reinforce the unstable rock mass, namely, rock bolts and cable bolts. Rock bolts are applied immediately after excavation, as a primary support system, to connect the fractured bedding plane to the immediate strata to create a beam. On the other hand, to enhance the durability of the excavation, long cable bolts are used as a secondary support system to connect and bind the bolted fractured zone to the higher competent stratification layers. Extensive research in the area of rock bolting with the aim of improving the load transferring mechanism of the bolting system has led the rock bolting technology to be enhanced enormously over the past four decades. Axial loading tests, known as the pull out test, have always been an accepted testing method to examine the tensile strength of tendons and load transfer capacity. Tendons refers to both rock bolt as well as cable bolts in this thesis. This type of test is relatively simple to design and perform both in the field and in the laboratory. Therefore, most available data on tendon performance deals with axial tensile testing. On the other hand, studies on shear behaviour of tendons are limited as shear tests can only be performed in the laboratory. The shear performance of tendons can be significantly affected by the ultimate tensile strength of the bolt, pretension load, rock mass strength, cable bolt surface profile, and cementitious/chemical resin properties. However, there is little known about the shear performance of tendon when installed at varying angles under quasi-static loading conditions. In addition, seismic events and rockburst are a pervasive problem in mines which operate at high extraction ratios and involve release and transmission of energy from the zone of influence of mining. Shear failure of rock bolts in mines are relatively prevalent, in particular in deep mines, which requires extensive research to understand the dynamic shear behaviour of tendons under high impact velocity loading conditions. Nevertheless, there is a lack of knowledge regarding the shear response of tendons under high impact loading condition such as rockburst events in underground mines and tunnels. Therefore, the current research study aims to provide a better understanding concerning the shear response of conventional rock bolts under high velocity impact loading conditions with the help of the laboratory experimental tests as well as numerical modelling approaches.