ABSTRACT
A considerable amount of coal reserves are located in protection pillars that lie under built-up region in active mining areas at the Czech part of the Upper Silesian Coal Basin. The commonly used controlled caving longwall mining method is not applicable in these areas because significant deformation of the surface is not permitted. For this reason the room and pillar method with stable coal pillars has been tested in order to minimise subsidence of surface.
Stress-deformation monitoring was essential as this was the first application of the conventional room and pillar mining method within the Upper Silesian Coal Basin mines. More than six kilometres of roadways were driven within two panels during last three years. To determine pillar stability, vertical stress and horizontal displacement of coal pillars were measured in coal pillars which are located within a row of pillars forming the panels. Two monitored pillars diamond in shape and slightly irregular sides have been observed into the first mined panel “V” and three monitored pillars have been observed into the second panel “II”. To measure the increase in vertical stress due to mining, hydraulic stress cells were installed in each coal pillar. The 5-level multipoint rib extensometers measured displacements of all sides within each monitored pillar. The results of stress-deformation monitoring allowed pillar loading and yielding characteristics to be described.
