Notable Contributions by Horst Wagner to Developing Safe Pillar Systems in Mining

The paper discusses some of the contributions Prof. Horst Wagner made during his professional career in South Africa and Austria to improve pillar mining operations in coal and hard rock mines. Most notable are the contributions to the understanding of coal pillar behaviour during loading of the pillar and, in particular, in the post peak loading regime. Using a novel test arrangement the contributions of different parts of the coal pillar to the support of overburden load could be shown. This has been instrumental to the understanding of pillar instability and the definition of effective pillar width in the case of non-square pillars. The main results of this work are now being applied worldwide. In pillar extraction mining new concepts to support the roof strata in the extraction line were developed. These have now become standard practice in Australian and US coal mines. A major breakthrough in combating the rock burst hazard in deep gold mines was the introduction of the stabilizing pillar system to control the energy changes associated with the extraction of narrow gold reefs a great depths.