Knox, G & Hadjigeorgiou, J 2022, 'Shear performance of yielding self-drilling anchors under controlled conditions', in Y Potvin (ed.), Caving 2022: Proceedings of the Fifth International Conference on Block and Sublevel Caving
, Australian Centre for Geomechanics, Perth, pp. 201-212, https://doi.org/10.36487/ACG_repo/2205_12
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 selfdrilling 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.
Keywords: self-drilling anchors, shear testing, bulk resin systems, mechanised mining
Bray, P, Johnsson, A, & Shcunnesson, H 2019 ‘Rock reinforcement solutions case study: Malmberget iron ore mine, Sweden’, in W Joughin (ed), Proceedings of the Ninth International Conference on Deep and High Stress Mining, The Southern African Institute of Mining and Metallurgy, Johannesburg, pp. 191–204.
Chen, Y & Li, C 2014 ‘Performance of fully encapsulated rebar bolts and D-Bolts under combined pull-and-shear loading’, Tunnelling and Underground Space Technology, vol. 45, pp. 99–106.
Chen, Y & Li, C 2015 ‘Influences of loading conditions and rock strength to the performance of rock bolts’, Geotechnical Testing Journal, vol. 38 no. 2, pp. 208–218.
Epiroc 2022a, Epiroc, Stockholm, viewed 10 June 2022,
Epiroc 2022b, Epiroc, Stockholm, viewed 20 May 2022,
Hadjigeorgiou, J & Tomasone, P 2018, ‘Characterising the behaviour of rockbolts based on in situ pull tests’, in Y Potvin & J Jakubec (eds), Caving 2018: Proceedings of the Fourth International Symposium on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 727–734.
Hagen, S, Larsen, T, Berghorst, A, & Knox, G 2019, ‘Laboratory full-scale rock bolt testing: analysis of recent results’, in W Joughin (ed), Proceedings of the Ninth International Conference on Deep and High Stress Mining, The Southern African Institute of Mining and Metallurgy, Johannesburg, pp. 217–230.
Hartmann, W & Hebblewhite, B 2003 ‘Understanding the performance of rock reinforcement elements under shear loading through laboratory testing - A 30 year history’, Proceedings 1st AGCM Conference, Sydney.
International Organization for Standardization 2019, Metallic materials - Tensile Testing – Part 1: Method of test at room temperature (ISO 6892-1:2019), International Organization for Standardization, Geneva.
Li, C 2010, ‘A new energy-absorbing bolt for rock support in high stress rock masses’, International Jounrnal of Rock Machanics & Mining Sciences, vol. 47, pp. 396–404.
Li, C, Stjern, G & Myrvang, A 2014, ‘A review on the performance of conventional and energy-absorbing rockbolts’, Journal of Rock Mechanics and Geotechnical Engineering, pp. 315–327.
Potvin, Y & Hadjigeorgiou, J 2020, Ground Support for underground mines, Australian Centre for Geomechanics, Perth.
Stjern, G 1995, Practical Performance of Rockbolts, PhD thesis, University of Science and Technology, Tronheim.
Thompson, A, Villaescusa, E & Windsor, C 2012, ‘Ground support terminology and classification: an update’, Geotechnical and Geological Engineering, vol. 30 no. 3, pp. 553–580.
Watt, G, Roberts, T & Faulkner, D 2018, ‘Single pass drill, install and inject self-drilling resin bolt applications in poor ground’, Proceedings of The Fourth Australasian Ground Control in Mining Conference Proceedings, The Australasian Institute of Mining and Metallurgy, Melbourne, pp. 323–343.