RESISTANCE OF YIELDING ROCK BOLTS TO MULTIPLE IMPACT LOADS
DOI:
https://doi.org/10.17159/Abstract
The paper presents the methodology and results of laboratory testing yielding rock bolt resistance to multiple impact loads exerted by means of a drop hammer. The methodology was based on standard ASTM D7401-08 as well as the test methodology and requirements specified for rock bolts by the 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 occurring during the studies, 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 of macro-deformed type yielding rock bolt (“Secura bolt”) resistance to multiple impact loads 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 damage. Damage to the bolt-resin contact in the upper anchoring zone of the bolt in the steel tube occurred in subsequent impacts. As a result, the macro-deformed bolt achieves additional yield, and its functioning following the shearing of the resin bond is similar to that of a “cone bolt”. Only one test, during the fourth impact, resulted in damage to the threaded bolt rod-nut coupling; however, no damage to the bolt-resin contact zone was observed.
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Copyright (c) 2024 Andrzej Pytlik, Donald O'Connor, Justin Graeme Corbett
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