The influence of drilling on the performance of a yielding self-drilling rockbolt

Authors: Abreu, R; Knox, G

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DOI https://doi.org/10.36487/ACG_repo/2205_09

Cite As:
Abreu, R & Knox, G 2022, 'The influence of drilling on the performance of a yielding self-drilling rockbolt', in Y Potvin (ed.), Caving 2022: Proceedings of the Fifth International Conference on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 165-176, https://doi.org/10.36487/ACG_repo/2205_09

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Abstract:
In recent years self-drilling anchors (SDA) have received increased attention from the ground support industry. This includes studies and field trials at Oyu Tolgoi mine in Mongolia and Malmberget mine in Sweden which have highlighted the installation success rate of SDAs in fractured rock masses. Typical challenges associated with rockbolt installation in such conditions include hole closures and blown out holes, resulting in a reduction of bolt installation success rates and achieved support capacity. To improve the efficacy of installation in fractured rock masses, an SDA replaces the conventional drill steel required to bore the support hole, combining both the drill steel and rockbolt into a single component. This negates the need for equipment to alternate between a drilling operation and bolt insertion as an SDA combines these traditionally separate processes into one. For squeezing and seismically active ground conditions, yielding SDAs offer an additional performance benefit derived from the ductile mechanical properties of the bolt from which these anchors are produced. However, a consequence of this bolt design is that the SDA is subjected to the percussive loading normally applied to the drill steel during the drilling operation, which can affect the performance of the bolt. This investigation quantifies the influence of this percussive drilling on the performance of a yielding SDA when subjected to dynamic loading. An experimental group of bolts were drilled into quartzite and thereafter subjected to impact testing in a laboratory. The performance of these samples is compared to a control group of samples, not previously subjected to drilling forces. This investigation provides insight into the in situ performance of a yielding self-drilling anchor.

Keywords: yielding self-drilling anchor, bulk resin systems, impact testing, mechanised mining, rock reinforcement

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