Reliability Analysis of Rock Supports in Underground Mine Drifts: A Case Study

Amoussou Coffi Adoko,Khamit Yakubov,Rennie Kaunda

doi:10.1007/s10706-021-02014-4

Amoussou Coffi Adoko, Khamit Yakubov + Show 1 more

Open Access

https://doi.org/10.1007/s10706-021-02014-4

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Abstract

Support failures in mine drifts represent potential hazards that threaten underground mine safety and productivity. The aim of this study is to determine the reliability index associated with the rock supporting elements used in Ridder-Sokolny mine, an underground mine located in East Kazakhstan. Numerical simulations of the drift support and the First Order Reliability Method (FORM) were employed to carry out the analysis. Several support cases were considered including: shotcrete, bolting, concrete, bolting combined with concrete and unsupported drift case. For each support case, the Factors of Safety (FS), the reliability index (β) and the Probability of Failure (PF) were determined in accordance with the corresponding rock mass quality and the excavation geometry. The results indicate a slight variation of the average FS values for the different support cases (except for shotcrete) while β and PF vary more significantly between 0.62–3.25 and 0.05–27 (× 103%) factor depending on the rock conditions and the installed support. The probability of failure of the rock support increases with a decrease in the rock mass quality. Similar trends are observed with an increase of the width/height ratio of the excavations for the same rock domain. These results illustrate that a single FS value obtained from a deterministic method may not always provide a sufficient indication of safety. This is in agreement with the field observations which have indicated a poor performance of the supports. Hence, on the basis of the reliability index of the supports, the requirement in terms of coefficient of variability of the rock mass quality to meet the target performance level is proposed. It is concluded that the results of this study could help improving the drift support design in Ridder-Sokolny mine.

Highlights

IntroductionDrifts are referred to as any type of horizontal or sub-horizontal development excavations with variable size, shape, and length depending on their purpose (exploration, ventilation or haulage)
In underground mining, drifts are referred to as any type of horizontal or sub-horizontal development excavations with variable size, shape, and length depending on their purpose
This study was aimed at performing a reliability analysis of the rock support elements in mine drifts

Summary

Introduction

Drifts are referred to as any type of horizontal or sub-horizontal development excavations with variable size, shape, and length depending on their purpose (exploration, ventilation or haulage). In one of the largest underground mines in the world, El Teniente copper mine located in Chile, approximately more than 3500 km of drift have been constructed to be able to extract copper ore (Elgenklöw 2003). With the depletion of shallow deposit around the world, mines have to construct drift much deeper with difficult geological settings, and support them. Several types of rock support and reinforcement may be required for ground control in the same drift. The main function of any drift support system in underground mines is to keep mine workers safe and equipment in the event of fall of ground. Several innovative supporting devices and methods of design of rock supports and have been proposed over the past few years and include numerical modeling (Boon et al 2015; Hu et al 2019; Nie et al 2018), empirical charts (Barton et al 1974; Chan and Einstein 1981; Rehman et al 2019), analytical methods including the key block theory (Fu and Ma 2014; Zhang et al 2020; Zou and Zhang 2019); probabilistic methods (Lü et al 2012; Oreste 2005); expert systems (Madhu et al 1995); lab and in-situ testing and monitoring (Bjureland et al 2019; Li 2006; Napa-García et al 2017; Wu et al 2019; Yokota et al 2020)

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