ABSTRACT

NIOSH has recently concluded an extensive blasting research and development program. One objective was to develop practical tools that encourage and facilitate the use of perimeter control in drift driving. NIOSH research suggests that proper design of the buffer row of the blastholes is the key to successful perimeter control. Specifically, if the buffer row of holes has been properly designed, the perimeter row of holes simply will do the final smoothing and shaping. Three blast damage models are presented and two blast design examples are described using model predictions. The paper concludes with recommendations for collecting the field experience to determine the optimum practical damage radius.

1. INTRODUCTION

Drift driving has always been an important part of underground mining. With the development of powerful drill jumbos, the introduction of bulk explosives in the 1980s, and the introduction of many new types of rock reinforcement, the overall process of rock excavation and support became very productive. An unintended consequence of advancements in extraction capability has often been less control of the extent of the damage to the surrounding rock, creating less stable ground control environments at times.

Today, some mines are placing more focus on the need to control the geometry of the drift opening using controlled blasting. Methods include the use of decoupled charges for back holes, short bottom charges to reduce the overall hole pressure, and the use of line drilling empty holes at the perimeter to provide a free face to stop perimeter damage. These methods are a positive development for both economic and safety considerations. To help achieve improvements in perimeter control, better strategies must be made available to the mining industry.

The National Institute of Occupational Safety and Health (NIOSH), as part of an effort to reduce accidents and injuries caused by falls of ground, has recently concluded an extensive research and development program aimed at improving blasting practices during drift driving. Poor blasting practices, which result in excessive overbreak and rock damage, are a possible contributing factor in these accidents. One specific objective has been to develop practical tools that encourage and facilitate the use of perimeter control in drift driving. The authors suggest that the proper design of the buffer row of blastholes is the key to successful perimeter control. If the buffer row of holes is properly designed, the perimeter row of holes simply must do the final smoothing and shaping. A number of different blast design approaches were investigated with the intent to provide an easy-to-use drift blast design software package that will allow engineers to study the complex interactions of blast design factors such as hole diameter, explosive properties, and careful perimeter blasting strategies, with the overall goal of reducing unnecessary overbreak and wall rock damage.

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