Experimental Analysis of Rockbolt Plate Strength Through Static and Dynamic Testing

Abstract

ABSTRACT A typical ground support system designed to safely excavate mine openings in rock consist of rockbolts, rockbolt plates, steel mesh, structural support lines, and shotcrete. The rockbolt plate, which connects the embedded rockbolt to the surface support, is a crucial part of a ground supporting system and is often the weakest link. Matching the correct embedded rockbolt to the rockbolt plate is crucial for proper ground support system interaction. If the selected plate is too weak, it will deform and will prevent full rockbolt yielding. If the plate is too strong, the system will take a lower cumulative load due to the lost energy dissipation potential of the plate and there will be no indication of rockbolt load due to the hindering of plate deflection. The rockbolt plate should deform during the yielding phase of the rockbolt, and fail after the reinforcing element. The ground support system must accommodate static and dynamic loading conditions and mechanical properties must be characterized to optimize rockbolt density and safety factor. CanmetMINING has developed a static and dynamic rockbolt plate testing regime using industry standards and innovative testing methods. The static testing methods are modified versions of standardized deflection tests. The dynamic testing methods were developed by CanmetMINING and include novel testing methodology. This paper describes the instrumentation and data acquisition methods, testing methodology, data processing method, and analysis of the static and dynamic test results from the tests. INTRODUCTION As the demand for critical minerals increases, there is additional pressure on mining operations to exploit new ore reserves, often in areas with more difficult ground conditions (Plouffe et al., 2008). In some cases, these orebodies are now found at depth, which poses additional ground control challenges due to higher in-situ stress conditions. To mitigate ground control instability, mining and ground control engineers carefully select appropriate reinforcement systems that may include rockbolts, mesh, and/or shotcrete (Potvin et al., 2010). At CanmetMINING's Ground Support Testing Laboratory in Ottawa, Ontario, Canada, linear reinforcement elements (i.e., rockbolt systems) can be evaluated under static and dynamic conditions. This detailed characterization of ground reinforcement elements is important for design engineers to understand the behavior of the ground reinforcement and therefore specify the appropriate reinforcement to counteract anticipated failure mechanism(s). This current research program focusses on the development of a method for evaluating rockbolt plate response under static and dynamic loading conditions for the purpose of improving plate characterization and contributing to improved rockbolt performance.