Dynamic testing: determining the residual dynamic capacity of an axially strained tendon
Conference: GROUND SUPPORT 2019, Sudbury, Canada
Authors: Greig Knox (South Africa) and Adrian Berghorst (USA)
Date: 23–25 October 2019
The specification of a tendon is stated as the capacity of the tendon in pristine condition on the day of delivery to the mine. A number of factors result in the degradation of the capacity of a tendon. Factors such as, but not limited to, installation quality, corrosion, and ground movement are all understood to reduce the residual capacity of a system. An understanding of the effects of the degradation of a tendon is important when determining the risk of an excavation. Rock support tendons are discretely tested quasi-statically (closure) or dynamically (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. This paper forms a basis for future work into determining the residual capacity of a tendon; the focus of this paper is to determine the residual dynamic capacity of an axially elongated tendon. Samples were axially elongated quasi-statically and fixed into place prior to being subjected to a single dynamic impulse (56 kJ), resulting in the rupture of the tendon, using the Dynamic Impact Tester from New Concept Mining. A trend of increasing ultimate dynamic load and total elongation (determined as the summation of the quasi-static and dynamic displacement) sustained prior to the rupturing of the tendon, was noted. However, the total energy absorbed by the tendon indicated the fact that the total energy of the tendon remained constant.