Analysis of the rock mass behaviour as associated with Ventersdorp contact reef stopes, South Africa

Abstract

In the Far West Rand Goldfields a series of lava flows covers the important, auriferous deposit known as the Ventersdorp Contact Reef (VCR), which separates the lavas from various sedimentary rock types. Until recently, little research had been done aiming at the identification and analysis of rock engineering problems encountered while mining this reef. This is especially surprising when considering that the VCR is one of the major South African gold producers, contributing some 15 % to the overall gold production. This dissertation consists of three parts: the first concerns the definition and establishment of geotechnical areas in all mines where the VCR is currently being mined. Twelve mines are considered covering a distance exceeding 60 km, and six major geotechnical areas are defined by regions with different combinations of hangingwall lavas and footwall rock types. The second part considers observations and measurements of the rock mass behaviour around geotechnically distinct VCR stopes. This approach is used as it is expected that geotechnical variation, influence rock mass behaviour and consequently mining strategy and design of support systems. The last part describes a VCR specific: stope support design methodology also considering closure rate variations as a function of face advance rates. (Abbreviation abstract)