Development of Chilean Open Stope Empirical Stability Database Using MineRoc and their Comparison with Literature

The optimal dimensions of stopes for underground mining using the Sublevel Stoping method are determined to guarantee the stability of the excavation. The graphical stability method developed by Mathews, later modified by different authors, is used as an analysis tool to achieve this objective. The stability graph plots the hydraulic radius of the stope wall against its stability number N. In this context, the MineRoc® software is used to perform the back analysis of overbreak of stopes walls exploited through Sublevel Stoping in Chile. A database of over 600 cases is developed, including Chilean geological, geotechnical, and operational conditions. This Chilean database is compared with literature databases, such as those of Mawdesley and Clark. Based on the comparison of databases, the scope of applicability of literature curves as design guidelines for sublevel stoping in Chile is established. Possible improvements to the empirical method to better reflect the conditions of Chilean mines are discussed. 1. INTRODUCTION The estimation of the potential instability of the rock mass around underground mine cavities is a subject of study in sublevel stoping (SLS) mining. Over the years, various tools have been developed for the design of unfilled stopes with the aim of improving these estimations. Mathews et al. (1981), based on a study of 26 historical cases in SLS, proposed the graphical stability method, in which a qualitative stability state is defined for each stope wall based on visual assessments and/or reconciled data. The method presented by Mathews became popular after the expansion of the original database and the recalibration of stability numerical factors. According to Madenova and Suorineni (2020), to date, there are five main variations of the stability graph: Potvin's modified Mathews stability graph (1988), Mawdesley and Trueman's expanded Mathews stability graph (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 stability graph based on dilution presented by Papaioanou & Suorineni (2015). Authors such as Nickson (1992), Suorineni (1998), Bewick & Kaiser (2009), Vallejos et al. (2016a, 2018a), Vallejos & Díaz (2020a), and Vallejos et al. (2022), among others, have also contributed by adding new historical cases to the original method, adapting some stability factors, and proposing new qualitative or quantitative boundaries. It should be noted that, in most cases, the stability graph has been adapted for other SLS operations (new site-specific conditions), narrow vein operations, and even for caving operations.