This paper focuses on the geotechnical analysis and slope design for the development of the Otjikoto gold mine in Namibia, with emphasis on the characterization and analysis of the sub-surface conditions for the proposed mine to the final pit depths. The geotechnical investigation was based on laboratory testing data, together with data from geotechnical boreholes. The analysis of the sub-surface conditions was assessed using the Laubscher (1990) Mining Rock Mass Classification System. The results were used for limit equilibrium analyses and confirmed using numerical methods. As the focus of the study was based in the classic rock mass classification systems, strength and experience is added to the knowledge base regarding these systems. This allows for a reference point to situations requiring similar solutions.

INTRODUCTION

Otjikoto gold mine is located approximately 300 km north of Windhoek, Namibia's capital city, between the towns or Otjiwarongo and Otavi (Figure 1). It is owned and operated by B2Gold Corporation and is currently in production. This paper presents the geotechnical feasibility study that was conducted prior to mine construction. Previous geotechnical investigations did not include orientated core drilling, and as such, a major gap was present in the geotechnical model. Data for the study was made available from dedicated orientated geotechnical holes drilled specifically for the project. The paper addresses the geotechnical nature of the intact rock, the joint strengths, and an analysis of bench and inter-ramp (stack) stability as well as overall slope stability.

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