Abstract

Turquoise Ridge Joint Venture underground mine (TRJV) consists of disseminated gold in very weak and altered limestones, mudstones, and carbon rich clays. These sediments are typically highly faulted and sheared, and are often bordered by highly altered dacite dikes. A more recent challenge has been mines going deeper and needing bigger and better single excavation .i.e. shafts to ventilate and provide ore skipping options. The stability concerns and shaft sinking method will be studied to evaluate the ground support needed and address with risk analysis to avoid costly and impractical decision made in the past.

The paper is an attempt to address the Geotechnical, hydrological, risk analysis to current technology and technical limits. Next five years several hundred millions dollars investment is expected for driving deeper shafts with innovative and sustainable technology to overcome current limitation. Also the author will address Engineering and support design criteria challenges to Northwest Nevada single excavation! Deep Shaft.

1. INTRODUCTION

The Turquoise Ridge Joint Venture (TRJV) is located in northern central Nevada, and is situated within the Basin and Range province, near the northeast end of the Osgood Mountains (see Figure 1).

The TRJV mine consisted of two major segments; the Getchell Main Underground (GMU) mine and the Turquoise Ridge (TR) mine segment. The Getchell underground segment is currently shutdown. Newmont has a 25% stake in the joint venture with Barrick controlling the remaining 75%. The primary product is high grade (>0.3oz/ton) Carlin-style gold mineralization in combinations of altered mudstones, limestone, and calcareous sediments.

The Turquoise Ridge Mine is entirely an underground mine, and is accessed by two shafts used for ventilation, men and materials transportation, and ore hoisting. The TR mine utilizes the underhand cut-and-fill mining method due to the relatively low rock quality in the ore zones and the relatively shallow dipping 25-45 degree ore body geometries. The primary ground control uses bolting, mesh, and shotcrete. It includes the use of cemented rock fill and a quick mining sequence to minimize ground exposure time and unraveling ground.

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