The application of a rock mass rating system at Tau Lekoa Mine

摘要

Rock mass rating systems have not been widely applied on South African gold mines, as there is a perception that they do not adequately cater for stress effects. Stress and stress induced fracturing are the dominant factors influencing rock mass conditions in most South African gold mines. Following visits to several mines in the Bushveld Igneous Complex, the authors were of the opinion that rock mass ratings could be successfully applied on Tau Lekoa Mine if stress fracturing could be incorporated. The successful application of a rock mass rating system at Tau Lekoa would assist in determining geotechnical areas. In addition, subjectivity in assessing ground conditions would be reduced and a greater level of consistency achieved. Various rock mass rating systems were evaluated in terms of their applicability to Tau Lekoa conditions and a variation of the Q-system was chosen as the most appropriate. Due to the variations in stress conditions and the impracticality of modelling every tunnel and sloping panel, conceptual modelling of various situations was conducted to determine stress look-up tables for various commonly encountered layouts. Currently the emphasis is on collecting sufficient data for the delineation of different geotechnical areas. Back analysis of ground conditions and support systems continues, with the aim of developing definite relationships between support requirements and the rock mass ratings.