An empirical comparison between new and existing laboratory-based dynamic sample configurations

Knox, Greig; Berghorst, A.; Bruin, Peter de

doi:10.36487/acg_rep/1815_58_knox

Cited by 6 publications

(3 citation statements)

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“…However, for multipoint anchor rockbolts, the split tube or continuous tube test represents the capacity of a single section of the rockbolt bounded by two anchors. For this reason, the direct impact split tube test was developed by Knox et al (2018b). A discontinuity in the host tube is placed between each anchor pair and consequently, the entire length of the rockbolt is loaded and the load is transferred through the distal anchor.…”

Section: Considerations When Reviewing Resultsmentioning

confidence: 99%

Laboratory-based drop testing of rock reinforcement

Knox

2023

Ground Support 2023: Proceedings of the 10th International Conference on Ground Support in Mining

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The requirement for resources has resulted in mining activities moving into more challenging conditions, from conventional, gravity driven ground conditions to highly stressed rock mass. In highly stressed, burst-prone rock masses, mining-induced seismicity presents a challenge to most ground support systems. The capacity of conventional rock reinforcement elements such as grouted rebar rockbolts and friction rockbolts is often found to be inadequate when subjected to large deformations resulting from mining-induced seismicity. The requirement to sustain large loads over large deformations has led to the development of several energy-absorbing rock reinforcement elements. The performance of an energy-absorbing element is typically determined through a laboratory-based drop test. During a laboratory-based test, the kinetic energy of a known mass, released from a known height, is transferred to the rock reinforcement element installed in a steel tube. There are two primary drop test methods, impact testing and momentum transfer. Although there are arguably differences between the two methods, both share common limitations. This paper provides a summary of recent investigations conducted to understand the effect of the test parameters on the performance of rock reinforcement elements determined through laboratory-based drop testing. The purpose is to provide a high-level overview rather a detailed review.

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Section: Considerations When Reviewing Resultsmentioning

confidence: 99%

Laboratory-based drop testing of rock reinforcement

Knox

2023

Ground Support 2023: Proceedings of the 10th International Conference on Ground Support in Mining

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“…Current testing is predominantly focused on lab testing for which tests are highly repeatable, and input parameters can be adjusted to gain an insight into how different parameters impact the capacity for single samples, e.g. Knox et al (2018), Knox & Berghorst (2019), Crompton & Knox (2022), Knox & Hadjigeorgiou (2022), and Abreu & Knox (2022). It is not possible to replicate certain underground conditions in the lab (installation quality etc.…”

Section: Laboratory and In Situ Testingmentioning

confidence: 99%

A review of ground support mesh testing around the world

Morkel,

Mikula,

Whiting

2023

Ground Support 2023: Proceedings of the 10th International Conference on Ground Support in Mining

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As mines around the world get deeper and the stresses around the excavations increase, the occurrence of large damaging seismic events (often called rockbursts) become more commonplace. One of the most favoured controls used in the industry to reduce damage from large seismic events is the implementation of a ground support system. Such a system typically comprises bolts or cables and surface support, such as shotcrete, mesh or screen, and straps.It is important to test all components of a dynamic ground support system, but there is a lack of useful testing done for surface support. Reviews and discussions of test results sourced from different test facilities show a wide scatter of energy absorption and deformation capacity. This, on top of concerns with testing setups, makes the consideration of surface support in support designs very difficult.In this paper, we discuss the current surface support testing results for mesh, and comment on whether current testing practices are producing useful metrics for geotechnical design.

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“…Tests of bolts under dynamic loading based on ASTM D7401-08 are conducted by internationally renowned laboratories in Australia, Canada, South Africa, and Sweden. There are many publications in the international literature that provide test results from laboratories Potvin, 2007, 2011) such as CANMET-MMSL (Labrie, Doucet, and Plouffe, 2008;Plouffe, Anderson, and Judge, 2008), the Western Australian School of Mines (WASM) Potvin, Wesseloo, and Heal, 2010;Villaescusa, 2009), the SRK drop weight test facility (SIMRAC Project GAP 423 (Ortlepp and Stacey, 1998)), and New Concept Mining in Canada and South Africa (Bosman, Cawood, and Berghorst, 2018;Knox, Berghorst, and Crompton, 2018;Knox, Berghorst, and de Bruin, 2018) and SINTEF, and the Norwegian University of Science and Technology (NTNU) in Trondheim (Hagen et al, 2020). Recently, the Central Mining Institute in Poland (GIG) has been conducting dynamic tests of bolts according to ASTM D7401-08.…”

Section: Introductionmentioning

confidence: 99%

Resistance of yielding rockbolts to multiple impact loads

Pytlik,

O'Connor,

Corbett

2024

J. S. Afr. Inst. Min. Metall.

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The resistance of yielding rockbolts to multiple impact loads was tested by means of a drop hammer. The methodology was based on the ASTM D7401-08 standard as well as the requirements specified for rockbolts by Luossavaara-Kiirunavaara Aktiebolag (LKAB - a Swedish mining company) and the Safety In Mines Research Advisory Committee of South Africa (project number GAP 423). During the tests, the loading force and bolt elongation were measured with a sampling frequency of fs = 19.2 kHz. In order to analyse the phenomena involved, the tests were recorded using two independent high-speed video cameras (600 and 1000 frames per second) and one thermal camera (128 frames per second). The tests demonstrated that all the samples transferred double the gravitational potential energy of Ep = 50.85 kJ from the impact load of mass m = 2825 kg and impact velocity of v = 6.0 m/s without failure. Damage to the bolt-resin contact in the upper anchoring zone of the bolt in the steel tube occurred after subsequent impacts. As a result, the macro-deformed bolt exhibits additional yield, and its operation following the shearing of the resin bond is similar to that of a 'cone bolt'. Only one test resulted in damage to the threaded bolt rod-nut coupling, during the fourth impact; however, no damage to the bolt-resin contact zone was observed.

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An empirical comparison between new and existing laboratory-based dynamic sample configurations

Cited by 6 publications

References 0 publications

Laboratory-based drop testing of rock reinforcement

Laboratory-based drop testing of rock reinforcement

A review of ground support mesh testing around the world

Resistance of yielding rockbolts to multiple impact loads

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