Authors: Crompton, BR; Knox, G

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Crompton, BR & Knox, G 2022, 'Dynamic testing: determining the relationship between rockbolt diameter and the residual dynamic capacity of an axially strained tendon', in Y Potvin (ed.), Caving 2022: Proceedings of the Fifth International Conference on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 141-150,

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The specification of a tendon is stated as the capacity of the tendon in new condition on the day it was produced. Rock support tendons are discretely tested quasi-statically (replicating closure) or dynamically (replicating seismicity) depending on the conditions expected with the mine environment. Although this testing is valuable, it is likely that a tendon subjected to rapid ground movement (seismicity) would first be subjected to some level of slow closure. Previous research investigated the possible correlation between the quasi-static elongation of a rockbolt prior to dynamic loading and residual dynamic capacity. The results from this research indicated that a correlation exists between the residual dynamic capacity and the energy absorbed quasi-statically when the tendon is elongated axially. It was proposed that a conservative approach would be to consider the total energy capacity of a tendon as the energy absorbed by a tendon in pristine condition during a single dynamic impulse resulting in the rupture of the tendon. The research sample set was limited to a single rockbolt configuration of fixed length and diameter, therefore it was noted that the results should not be extrapolated to other versions of this system or other ground support systems. This research will build on the previous work by repeating the testing regime on a larger diameter of the same configuration rockbolt. The results will be analysed to identify how the diameter of a rockbolt affects the energy and elongation capacity of the rockbolts under combined quasi-static and dynamic loading. This information will greatly assist geotechnical practitioners with support system design, product selection and decisions on when to rehabilitate an installed support system.

Keywords: dynamic testing, ground support, pre-elongated, squeezing ground, seismicity, rockbolt, PAR1 Resin Bolt, Dynamic Impact Tester

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