Assessment of geotechnical considerations for ground control and stability in the synclinorium area at Nkana mine of Zambia

Abstract Nkana Synclinorium is in the southern part of the Nkana mining license area. The orebody structure of the mine is characterized by complex folding, with anticlines and synclines. Due to increase in mine depth, mining operations have been encountering geotechnical challenges related to ground control and ground stability. The mine has witnessed an increase in fall of ground accidents in the last 5 to 9 years. This study assesses the ground control mechanisms, support standards and evaluates the design, installation and quality control of rock support in order to establish adherence to ground control and stability requirement at the mine. A number of factors were examined: historical and current geotechnical data; geological structures; pillar support and reinforcement requirements and excavation design practices. The study applied borehole logging to obtain geotechnical data, scanline mapping for geological structures, numerical modeling and empirical methods in the assessment of pillar design. Results of the study indicate that geological structures are major contributors to rock instability around underground excavations at the Synclinorium mine. Using the rock mass rating system, it is indicated that rock types of sedimentary nature, like Shale are associated with most of the ground instability at the Synclinorium mine.