Investigation of Excavation Length Effect on Stope Stability at a Canadian Hard Rock Mine
Authors: Huawei Xu , Derek B. Apel 
Published: September 2023

ABSTRACT
In underground mining, stopes are excavated step by step, and each step has a certain length according to the mine planning. Displacements of the free surface of the stope sidewall are contributed by the excavation of stopes. Rockburst is caused by the exaction in underground stopes in rockburst proneness rock mass, especially in deep underground mines. In this paper, the stope excavation length effects on the displacement and rockburst in underground stopes induced by excavation were investigated by numerical modelling analysis. Five different stope excavation length scenarios were proposed and performed to study the effect of excavation length on the stope stability at a Canadian hard rock mine. With different increasing phases during displacement initiation and rockburst development, all five excavation scenarios achieved almost the same final results in rockburst tendency and displacement at the analyzed location on the stope sidewalls. Compared with the other four excavation scenarios, scenario SCN#1 is more effective and efficient in numerical simulation analysis, especially for the numerical simulation analysis of the full-size underground mine.

INTRODUCTION
As underground mining works progress into deeper and more complex geological environments, they are experiencing more stress-induced rock damage initiation problems, which have seriously impeded mining efficiency and effectiveness (Kaiser et al., 2000). To better understand underground mining stope convergence and deal with the rock mass damages during the excavation, many researchers are actively addressing these issues. Barla (Barla et al., 2010; Barla et al., 2012; Barla & Pelizza, 2000) proposed several approaches for stope design by assessing the interaction between rock mass and structures in rock mass with time-dependent squeezing behavior. Janoszek (Janoszek, 2020) proposed two indexes to predict natural hazards in longwall working with analysis of coal and roof properties, interaction in shield loading and roof-floor by numerical modelling based on the Mohr-Coulomb criterion. Rock mass squeezing phenomenon around the stopes are widely investigated by considering the different rates of advancing (Ghaboussi & Gioda, 1977), analyzing the extension of microcrack length and development of excavation damage zone (Golshani et al., 2007; Tang et al., 2018), time-dependent deformation, and elastoplastic behavior (Malan, 2002), in the means of semi-empirical back analysis approach (Manh et al., 2015), analytical solution (Sulem et al., 1987), and numerical modelling (Ghaboussi & Gioda, 1977; Golshani et al., 2007; Manh et al., 2015; Wang & Huang, 2011; Weng et al., 2010; Xu & Apel, 2020). Gioda (Gioda & Cividini, 1996) discussed the linear and non-linear viscous constitutive laws and developed numerical methods to analyze the time-dependent effect on performance in squeezing rocks. The interaction mechanism between the stope excavation and stope stability was studied by analyzing the supports, physical model tests, underground research laboratory measurement, and numerical simulation (e Sousa et al., 2012; Funatsu et al., 2008; Martino & Chandler, 2004; Vazquez-Silva et al., 2020; Xu, 2021; Yuan & Yang, 2021; Zhang et al., 2019).