Wave-like character of rock pressure in a longwall face

Abstract

Introduction. Coal seam extraction causes rock mass displacement, which often leads to negative consequences. It is important to take into account the process patterns within the undermined rock mass to reduce the negative effect. Intensifi ed mining operations, increased lengths of faces and extraction panels, and increased per face output inevitably cause changes in all geomechanical processes in the face. Research theory. When designing and developing the working area, it is important to examine and forecast the geomechanical situation, as well as take into account the parameters and elements of the displacement processes caused by coal seam mining. The research objective is to determine the infl uence patterns in the rock seam that exerts pressure on mine support. The article presents the results of pressure area construction when mining longwall faces in gently sloping coal seams. Methods of research. Rock pressure on a power support unit was monitored based on pressure readings in the legs using Marko company data. The Surfer software product was used to build the pressure area and its profi les. The pressure area is obtained by converting the fl uid pressure in power support legs into rock pressure. The variation of the longwall support pressure during coal seam mining is shown. Results and analysis. The paper proposes an algorithm for calculating the thickness of the seam that exerts pressure on the longwall face support. The algorithm considers its wave-like changes along the length of the panel. The thickness of rocks exerting pressure on the support is up to 10 seam thicknesses. Conclusions. The height of the pressure arch generally coincides with the parameters for the disordered collapse zone. It is 4–8 times as big as the thickness of the extracted seam. The process of roof collapse and displacement a longwall face is wave-like. The height of the pressure arch can be determined using a sinusoid and the concepts of rock mass structuring according to the algorithm presented in this paper