The specification of a tendon is stated as the capacity of the tendon in pristine condition on the day of delivery to the mine. A number of factors result in the degradation of the capacity of a tendon. Factors such as, but not limited to, installation quality, corrosion, and ground movement are all understood to reduce the residual capacity of a system. An understanding of the effects of the degradation of a tendon is important when determining the risk of an excavation. Rock support tendons are discretely tested quasi-statically (closure) or dynamically (seismicity) depending on the conditions expected with the mine environment. Although this testing is valuable, it is likely that a tendon subjected to rapid ground movement (seismicity) would first be subjected to some level of slow closure. This paper forms a basis for future work into determining the residual capacity of a tendon; the focus of this paper is to determine the residual dynamic capacity of an axially elongated tendon. Samples were axially elongated quasi-statically and fixed into place prior to being subjected to a single dynamic impulse (56 kJ), resulting in the rupture of the tendon, using the Dynamic Impact Tester from New Concept Mining. A trend of increasing ultimate dynamic load and total elongation (determined as the summation of the quasi-static and dynamic displacement) sustained prior to the rupturing of the tendon, was noted. However, the total energy absorbed by the tendon indicated the fact that the total energy of the tendon remained constant.

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SynopsisRockbolting is a method used for rock reinforcement in underground mining and tunnelling. There is a large variety of different types of rockbolts with different support functions. The behaviour of a rockbolt in a rock mass depends on the function and material of the bolt itself, combined with the mechanical properties of the rock mass, deformation capacity, strength, and level of stress. Testing of rockbolts in full-scale laboratory-controlled conditions is therefore of great importance. At the rock mechanics laboratory of SINTEF and the Norwegian University of Science and Technology (NTNU) in Trondheim, a rockbolt test rig has been developed for full-scale testing for pull, shear, and combination pull-shear tests. In this paper we describe the principles behind this quasi-static full-scale testing and include the results and analyses of recent tests on different types of rockbolt. The applicability of the test rig for rockbolt selection and rock support design is also discussed.

Rock bolting is a method used for rock reinforcement in underground mining and tunnelling. There is a large variety of different types of rock bolts with different support functions. The behaviour of a rock bolt in a rock mass depends on the function and material of the bolt itself, combined with the mechanical properties of the rock mass, deformation capacity, strength and level of stress. Testing of rock bolts in full-scale laboratorycontrolled conditions is therefore of great importance. At the rock mechanics laboratory of SINTEF and Norwegian University of Science and Technology (NTNU) in Trondheim, a rock bolt test rig has been developed for full-scale testing for pull, shear and combination pull-shear tests. This paper describes the principles behind this quasi-static full-scale testing and includes the results and analyses of recent tests performed on different types of rock bolts. It also discusses the applicability of the test rig for rock bolt selection and rock support design.

The traditional installation of grouted rockbolts requires a support hole to be pre-drilled followed by the installation of a cementitious or resin grout. The rockbolt is then inserted into the grout. In highly stressed or poor ground, the presence of fractures, shear features and altered rock can lead to unravelling of the support hole and result in blockages and grout losses. Consequently, the support holes are often redrilled, resulting in oversized holes, increased installation times, and poor installation quality.Replacing the conventional drill string with a self-drilling anchor (SDA) improves both the quality and advancement rate of installation. These are critical considerations in poor ground. The SDA rockbolt is coupled to the rock drill, drilled to depth, then decoupled and post grouted. This one-step installation method overcomes the challenges of drilling into fractured rock where hole closures and grout losses are common. The operational advantages of the application of a one-step system using self-drilling anchors have recently been demonstrated in two caving operations, Oyu Tolgoi mine in Mongolia and Malmberget mine in Sweden.A yielding SDA offers additional performance benefits when in squeezing rock or seismic prone ground. There is limited data on the response of yielding self-drilling anchors to tensile and shear loading under controlled laboratory conditions. The undertaken experimental program has investigated the behaviour of a yielding SDA under tensile and shear loads. This contributes to an improved understanding of the response of self-drilling anchors under a single loading mechanism and can provide an indication of performance in highly stressed and fractured rock observed in caving operations and deep underground mines.