A Rock Mechanics Perspective on the effects of Hard Rock workings in close proximity to overlying Coal Seams

Mining in the Coalfields has been ongoing for many years, however prior to the discovery of coal, Gold was being mined in the form of the Kimberley Reef. Today it is the coal that has our interest and is the primary mineral being extracted from the ground. This has led to the purpose of this paper which ultimately looks at the effects of historic hard rock workings that are in close proximity to overlying coal seams at the Sasol colliery. Two sections (37 and 49) were monitored to assess the effects that the Kimberely Reef has on the current mining of coal below. The importance of the study was that resultant stress interactions could hinder mining in terms of safety concerns, production losses and additional costs. Underground analysis and monitoring of the area concerned has concluded that additional stresses from the gold mine caused sidewalls in the coal mine to scale and slab. The damage to the roof was evident in terms of ride. This had a negative effect on production, costs and created safety concerns