Experimental Assessment of the Energy Dissipation and Deformation Capacity of Ground Support Systems Under Dynamic Loading: Insights from LaRonde Mine Dynamic Drop Test Program

Abstract

ABSTRACT: Over its 30-year history, the design of ground support schemes at the LaRonde mine has evolved significantly to meet the demands of the rock mass while mining from surface to the current depth of over 3000 m. Over the past decade, seismicity and dynamic loading on ground support systems have become a focus of ground control management and one of the major challenges at LaRonde mine. In some rare occurrences, dynamic loading from seismic events have exceeded the capacity of ground support schemes. Furthermore, the ground control practices implemented to safely manage seismic conditions in development drives have been largely successful despite the operational challenges of a deep mine. Thus, as the mine progresses ever deeper, there is a continuous need to implement ground support schemes that are not only tougher but also more efficient to install considering the mine configuration and available equipment. As part of this endeavor, a dynamic testing program was developed at Geobrugg's testing facility, in association with Geobrugg and the Kittilä mine. The test program involved various elements of ground support schemes from LaRonde and Kittilä mines. This paper presents the testing program, instrumentation set up and results analysis process as well as testing results for three of the LaRonde tests. The testing program is intended to guide improvements in ground support schemes designs for deep mining environments. 1. INTRODUCTION Deep underground mining environments present unique challenges for the design of ground support schemes, particularly in zones susceptible to stress-induced rock failure and rockbursting. Traditional ground support schemes, designed primarily to control gravity-induced rockfalls in blocky rock masses, have been found to be unsuitable for such environments. For the sake of consistency, the authors have adopted the terminology proposed by Windsor and Thompson (1992) as presented in Villaescusa et al (2023). A Ground Support Scheme is therefore defined as a combination of a surface support system, composed of plates, mesh, liner or shotcrete, with an internal reinforcement system consisting of rockbolts and cable bolts. In blocky ground, under static conditions, the design of a ground support scheme aims primarily at meeting the load demand and minimizing deformation to maximize the reinforcement function. In weak and highly deforming ground, ground support schemes require increased ductility to meet the deformation demand while retaining load capacity. Under dynamic conditions, the ground support schemes must also satisfy energy dissipation, rapid rock mass deformation demands and ensure load transfer from the rock mass to the reinforcement, and to the surface support. The ground support elements' load and deformation characteristics must be matched to enable this load transfer.