The Mechanical Performance of Solid Reinforcing Bar Rockbolts
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ORIGINAL PAPER
The Mechanical Performance of Solid Reinforcing Bar Rockbolts Bre‑Anne Sainsbury1 · Nurses Kurucuk1 · John Bolton2 Received: 26 September 2019 / Accepted: 25 June 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract The strength of a rockbolt is one of the key parameters for the design of ground support systems. However, published mechanical performance data by suppliers are usually limited to tensile strength and elongation. To provide additional performance measures, mechanical tests on four commercially available solid reinforcing bar rockbolts have been performed and analysed. In each of the cases, the rockbolts are marketed by the manufacturers as being similar and equivalent products. The mechanical tests have been developed to mimic five modes of failure that include tension, shear, torsion, and nut/thread interface. The results show significant variability in seemingly similarly marketed products. Recommendations are made for suppliers to provide additional testing results (torsion, shear and nut/thread capacity) as standard data within their product specification sheets. A summary of recommended design parameters is provided based on the test results. Keywords Rockbolt · Mechanical properties · Tensile response · Shear response · Torsion response
1 Introduction Within an underground excavation, both surface and embedded support elements are used to stabilize the ground response. Depending on the frequency of use and expected life span of the excavation, mesh and friction bolts or shotcrete and solid reinforcing bars are typically used. This research focuses on the performance of solid reinforcing bars (rockbolts) that have a higher design support capacity than friction bolts, since they are anchored to the rock mass via grout or resin and are able to be pre-tensioned. Fully encapsulated rockbolts have been widely used as reinforcement elements in mining and tunnelling for many years due to economic benefits and advances in rockbolt system technologies (Saadat and Taheri 2019). The mechanical performance of rockbolts has previously been considered through a variety of laboratory and in-situ testing programs that include, for example, resin/ bond strength (Li et al. 2016), pull-out strength (Kristjánsson 2014), and corrosion (Meikle et al. 2017). This research provides a summary of some novel mechanical testing that * Bre‑Anne Sainsbury [email protected] 1
School of Science, Engineering and Built Environment, Deakin University, Waurn Ponds, VIC, Australia
Minova, Richmond Vale, NSW, Australia
2
has been completed in a laboratory environment to consider the performance of four of the most common commercially available rockbolts. In each of the cases, the rockbolts are marketed by the manufacturers as being similar and equivalent “resin” or "chemical” rock reinforcement products for use in hard rock mines. They are described as solid reinforcing bars that are usually fully encapsulated with resin during installation (fully encapsulated resin
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