ABSTRACT:

The development of new, more advanced mining methods, particularly open stope mining, has led to significant increases in productivity in underground hard rock mines. Unfortunately this improved productivity was often accompanied by significant dilution. The development of larger capacity mobile underground equipment, which directly contributed to the development of higher productivity, higher tonnage, mining methods, requires larger underground access infrastructure. These and other factors necessitated that significant improvements be made in the area of basic ground control and rock engineering. This paper reviews some key rock engineering developments from the past 15 years and how these impact

INTRODUCTION

It is often stated that rock mechanics, and particularly applied rock engineering, form the backbone of mining. However, until recently, rock mechanics and applied rock engineering exerted very limited direct influence on underground mine design. The development of new, more advanced mining methods, particularly open stope mining, has led to impressive increases in productivity. Unfortunately this improved productivity was often accompanied by significant dilution. In fact, uncontrolled dilution has led to the closure of a number of mining operations in Canada in the late 70's and 80's [Tintor, 1988].

The modem drive for 100% extraction of the mineral resource, made possible by new mining methods, improved backfill and other ground support techniques, provides far superior husbandry of scarce natural resources, and is particularly economically attractive when viewed from the perspective of the cost of reserve replacement. At the same time, in most major mining countries, mining has pushed to ever-greater depths. The combination of very high extraction ratios and increasing depth is often accompanied by serious mine induced seismicity problems. In some cases these have also led to premature mine closure. The development of larger capacity mobile underground equipment, which directly contributed to the development of higher productivity, higher tonnage underground mining methods, also necessitates larger underground access infrastructure. Stability and safety problems associated with access drives tend to increase nearly exponentially with increasing size.

All of these factors required significant improvement in the area of basic ground control. Improved ground control is a complex function of the rockmass characteristics, stope sequencing and resulting mine induced stress redistribution and ground support design and reliability. These areas form the core of modem geomechanical mine design.

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