Case Studies of Rock Bolt Support Loads and Rock Mass Monitoring for the Room and Pillar Method in the Legnica-Głogów Copper District in Poland

Krzysztof Skrzypkowski

doi:10.3390/en13112998

Abstract

The article presents the impact of geological and mining factors on the stability of room excavations in the Legnica-Głogów Copper District (LGOM) in Poland. In underground mining, the primary task of bolting of mining excavations is to ensure their stability as an essential condition of work safety. Appreciating the role and importance of the rock bolting in Polish ore mining; rock bolt load sensors were designed, manufactured and tested under laboratory conditions. The purpose of the research was to characterize the sensors and determine the elastic range of the bearing plate, which are an integral part of the sensor. The sensors have been verified in industrial conditions. The tests were carried out in the underground copper ore mine in Poland. Three rooms in the exploitation field were selected for testing, where exploitation was carried out at a depth of 809–820 m below the ground surface with the application of room and pillar with roof deflection and maintaining the central part of the field. The exploitation field included 60 rooms and pillars. The effectiveness of the mechanical load sensor of the expansion rock bolt support has been experimentally confirmed. Based on mine research, it was found that the largest increases in the load of the rock bolting, vertical stress and convergence occur in the middle of the mining field.

Highlights

One of the conditions for safe exploitation of ore deposits is the ability to maintain the specific geometrical parameters of a room excavation for a certain period of time
In the case of dynamic loads resulting from blasting works or natural tremors, the crew is required to tear off hazardous rocks before commencing work in a given shift, or secure with a support those solids that cannot be broken
It should be stated that RFRI index does not take into account technological factors related to the mining system

Summary

Introduction

One of the conditions for safe exploitation of ore deposits is the ability to maintain the specific geometrical parameters of a room excavation for a certain period of time. In this case, the stability of the room is determined by the limit span of the roof. There are cases that at spans smaller than limit, due to structural disorders, there are symptoms of local instability in the form of roof falls or stratification of the roof. Based on observation and research in industrial conditions, various rock mass classifications are developed to assess local instability. One method for estimating the impact of these parameters is the RDi classification [3]

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Conclusion