Instability Assessment of Hanging Wall Rocks during Underground Mining of Iron Ores

Oleg Bazaluk,Vasyl Lozynskyi,Serhii Zubko,Mykhailo Petlovanyi,Kateryna Sai

doi:10.3390/min11080858

Abstract

The paper presents the study of the deformation processes development in unstable rocks of the hanging wall during mining a thick steeply dipping ore deposit in the example of the Yuzhno-Belozerskyi deposit. In the studied field, there are problems of stability of hanging wall rocks, represented by low-resistant shale rocks that do not withstand significant outcrops in time. A decrease in stability is manifested in the form of failure of the hanging wall rocks into the stope. Based on a detailed study of the ore deposit geological structure and the performance of the stopes mining, according to the survey data, an area of the deposit has been identified where the ore failure and dilution reach 4%–8% with a maximum value of 12%. This also makes it possible to determine the most important averaged source data for performing physical modeling on equivalent materials. It has been determined that the deformation value of the hanging wall rocks with subsequent failure into the stope and ore mass deformation in the sloping bottom change exponentially with an increase in the depth of the stope location, and the dynamics of increasing rock deformations in the hanging wall is noticeably higher than in the sloping bottom of the stope. This reduces the quality of the mined ore and increases the probability of rock failure area propagation to the hanging wall drifts with their subsequent destruction. The results of physical modeling are characterised by acceptable reliability and are confirmed by a high similarity with the actual data on ore dilution with broken rocks during the stopes development. It has been found that during the formation of a steeply dipping outcrop of stopes with an area of 1200 m2, unstable rocks of the hanging wall are prone to failure of significant volumes. For successful mining and achieving stope element stability, it is recommended to optimise its parameters, the height, width and the value of a steeply dipping outcrop, as well as to preserve the ore pillar in the hanging wall until the ore is broken and drawn from the rest of the stope.

Highlights

In underground mining, including iron ore mining, the issues of rock mass stability are always important, since the safety of workers, the quality of minerals and the preservation of the Earth’s surface depend on it
This paper studies the deformation processes development in the hanging wall rocks during the mining of thick ore deposit at the Yuzhno-Belozerskyi field, the most valuable in terms of iron ore content in Ukraine
As a result of the research, the following scientific and practical results have been obtained, which are useful for an effective technology for ore mining in unstable rocks: 1. During mining within the depth interval of 640–940 m in the central and southern zones of the deposit, problems arise with the hanging wall rocks’ stability, represented by quartz-chlorite-sericite shales, sometimes talcose shales of low hardness of f = 4–9 that do not withstand significant outcrops in time

Summary

Introduction

In underground mining, including iron ore mining, the issues of rock mass stability are always important, since the safety of workers, the quality of minerals and the preservation of the Earth’s surface depend on it. This is especially important for mining the valuable ores with chambers (stopes) of large sizes, when the stage-by-stage breaking of their reserves gradually increases the area of outcropping the hanging wall rocks and redistributes the stress-strain state, which requires direct attention in practice, and an assessment and prediction of stability should be undertaken. As well as environmental factors, are taken into account when developing progressive technologies of minerals mining [9,10,11] and providing stability of geo-technological and geological structures [12,13,14,15]

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Results

Conclusion