Laboratory testing of a long expansion rock bolt support for energy-absorbing applications

Krzysztof Skrzypkowski

doi:10.1051/e3sconf/20182900004

Abstract

The main purpose of rock support and reinforcement in underground mining is to maintain excavations safe and open for their intended lifespan. The basic type of rock mass reinforcement method both in ore and hard coal mining is rock bolt support. Very often, existing bolt support systems are not always capable of providing a reliable controlled performance. Therefore, in recent years energy-absorbing bolts which are exposed to dynamic loading, for example from rock burst caused by high rock stresses, earthquakes, or blasting have appeared. In this article particular attention was paid to short and long expansion bolts. Quasi-static tests of expansion bolts were carried out at the laboratory test facility in simulated mining conditions, especially for the KGHM Polska Miedź S.A. mines. In the underground mines of the Legnica-Głogów Copper District (LGOM) the main way to protect the room excavation is rock bolt support with a length from 1.2 m to 2.6 m. Rock bolt support longer than 2.6 m is considered as additional support of excavations and is increasingly being used to reinforce the roofs. The comparisons of energy-absorbing short and long expansion bolts with a length of 1.8m, 3.6m and 5.2m were presented. In addition, for elastic and plastic range of each bolts were determined.

Highlights

Many mines around the word, for example those in Poland, Chile, Canada, Australia and South Africa, are currently being operated at depths greater than 1000m
Mining supports must be adapted to the natural hazards, especially rock bursts, whose intensification will be increasing with the increase in depth of exploitation [2, 3]
Energy-absorbing bolts are used as part of rock support systems in underground mines that are exposed to detonating explosives and rock burst

Summary

Introduction

Many mines around the word, for example those in Poland, Chile, Canada, Australia and South Africa, are currently being operated at depths greater than 1000m. At such levels, the rock mass can be highly stressed causing an increase in the severity and frequency of rock bursts. The consequence of the execution of any underground excavation is the formation of a new equilibrium state defined by the difference between the original state of stress and displacement This is accompanied by specific geotechnical processes, their type and intensity being a function of the stress state and geomechanical properties of the rocks surrounding the excavated area.

Objectives

Methods

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Conclusion