Geotechnical Analysis for Narrow Vein Mining Using MineRoc® Software

Abstract

ABSTRACT: The prediction of rock mass stability in sublevel open stoping (SLOS) and narrow vein (NV) mining is performed in the design process to estimate the stope size required to reduce operational hazards and achieve continuous production. For almost four decades, the Stability Graph method has been used for this purpose. Several improvements of the Stability Graph method have taken place through the years. However, there is still work to be done. Accordingly, new case studies need to be continuously collected to update the Stability Graph. Then, in the back-analysis of open stopes, performance parameters related with the geometry are calculated, and a stability state is assigned to each case study. When these tasks are systematically performed, the Stability Graph can be calibrated, delineating more reliable new stability boundaries to a specific site condition. However, some problems in the collection of new case studies in SLOS and NV operations such as disorder in geotechnical data or miscalculation of performance parameters impede the correct improvement of the stability boundaries. To deal with these problems, several computational tools have been developed and integrated into the software MineRoc®. This paper shows a geotechnical process of a narrow vein mine using MineRoc®. New features of the software and the illustration on how MineRoc® positively impacts on the mine design and planning processes are also presented. 1. INTRODUCTION The potential for instability in the rock mass surrounding underground mine openings is an ever-present hazard to the safety of people, equipment, and operations in both sublevel open stoping (SLOS) and narrow vein (NV) mining. Several tools for the design of open stopes have been developed over the years with the purpose of reducing these threats. Mathews et al. (1981), based on a study of 26 case histories in SLOS, proposed the stability graph method in which a qualitative stability state for each open stope surface is given based on visual evaluations and/or reconciled data. The graph introduced by Mathews et al. (1981) became popular following the expansion of the original database and/or the re-calibration of the stability number factors. According to Madenova & Suorineni (2020), to date, five major stability graph variations exist: the Modified Mathews’ stability graph by Potvin (1988), the extended Mathews’ stability graph by Mawdesley & Trueman (2003), the equivalent linear overbreak slough (ELOS) stability graph proposed by Clark & Pakalnis (1997), the stability graph for cable bolt support design proposed by Diederichs et al. (1999), and the dilution-based stability graph introduced by Papaioanou & Suorineni (2016). Authors such as Nickson (1992), Suorineni (1998), Bewick & Kaiser (2009), Vallejos et al. (2016a, 2018a), and Vallejos & Díaz (2020a), among others, have also contributed adding new case histories to the original method, adapting some stability factors and proposing new qualitative stability boundaries. Note that in most cases the stability graph has been adapted for other SLOS operations (new site-specific conditions), NV operations and even for caving operations.