Dependence of active volume of the rock mass on the advance rate of a longwall coalface

Author: J. Drzewiecki

The process of mining coal seams by the long wall system causes the occurrence of a number of discontinuities in the overlying rock mass with directions varying in relation to its stratifaction. The area of the rock mass shead of the longwall coalface subjected to this process is characterised by a changing geometry depending, among other things, on the advance rate of the longwall coalface.

The horizontal extent of this area in the direction of the longwall coalface drive advance is directly prQportional to this advance rate, and the vertical extent is inversely proportional. This area is called the "active volume of the rock mass".

A method to determine this volume, together with empirical relationships and the kinetic parameter of the effect of mining for isolated layers contained in this volume are presented.

The consequences of variations in the advance rate of the longwall coalface in a mine working are also discussed.