ABSTRACT:

In order to determine the dynamic capability of a Garford hybrid bolt, static and dynamic tests were performed at the Videx Mining facility in South Africa. Two hydraulic rams with a capacity of 300kN and a total displacement of 300mm were used to determine the static performance of the bolt. The operation of the hydraulic rams was accomplished using an electric pump. The electric pump was used from the initial phase of loading until the bolt reaches specimen fails, or the rams reach their stroke capacity (300mm). On the other hand, drop tests were performed using known mass from a known height dropped onto a plate connected to bolt specimen installed. The results of the study indicated that Garford hybrid bolts can withstand the maximum peak load of 217.95kN with a minimum peak load of 138. 18kN. This was achieved at a test time between 17.50 seconds to 21.40 seconds. Further analysis has shown that the bolt can achieve the energy absorption ranging from 22.06kJ to 22.21kJ at a velocity ranging from 2.90m/s to 3.28m/s.

1 INTRODUCTION

Previous studies such as those conducted by, Tannant and McDowell (1992); Tannant et al. (1992a; 1992b); McDowell and Tannant (1995); Hagan et al. (2001); Moreau et al. (2003); Archibald et al. (2003); Heal (2005); Andrieux et al. (2005); Plouffe et al. (2007); Sengani and Kataka (2017a) and Sengani and Kataka (2017b), have indicated that most of the underground excavations require ground support to maintain excavation stability and to ensure a safe environment for personnel and equipment. The studies have reported that an appropriate ground support design matches the characteristics of support elements (e.g. steel tendons, screen, straps, shotcrete, etc.) with the anticipated rock mass behaviour (e.g. the response to variations of loads and displacements over time). Plouffe et al. (2007) has shown that engineers should consider both static (i.e. supporting the weight of the surrounding rock with stiff ground support systems) and dynamic conditions (i.e. surviving additional forces, which may be imposed instantaneously and without warning, such as a rockburst, using yielding ground support systems). However, it difficult to predict and design a support system that can withstand dynamic conditions.

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