3D laser scanning is a unique technology used for the description and subsequent modeling of real shape of spatially complex underground mining environment. Groundbreaking was its application in the pilot deployment of the Room and Pillar method at the CSM mine, where this method was used for the first time within the Upper Silesian Coal Basin, also known to have one of the most difficult mining and geomechanical conditions in the world. Very difficult mining conditions at depth over 800 m warranted searching for complex geotechnical tool or method that would capture all changes without distortion. Despite some shortcomings, 3D laser scanning was selected, although there is still no suitable device for dusty and humid mining environment. During the pillar development phase, comprehensive geotechnical monitoring was undertaken including the frequent scanning of pillar movement using 3D laser scanning technology. Based on repeated time-separated measurements, spatio-temporal analyses of deformation changes during ongoing mining were carried out. These analyses captured dynamic changes in coal rib, roof and floor movements of designated roadways while developing the pillar panel. In addition, time dependent long term post-mining measurements quantified additional strata movements within the panel enabling assessment of the long term pillar and mine roadway stability. The time-lapse scanning indicated variable pillar rib movement with maximum measured displacements of 60 cm. The scans indicated that in most cases, the bottom of the seam displaced more than the top of the rib side due to low floor strength causing large floor heave of up to 100 cm. During the 3-year monitoring, more than 2 billion spatial points were captured that can be used for further analysis.
A considerable amount of coal reserves are located in protection pillars that lie under built-up region in active Czech mining areas 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 modified room and pillar method with stable coal pillars has been tested in order to minimise strata convergence. The trial operation of room and pillar method has been implemented at the shaft protective pillar where no mining was carried out in the past. Mining depth of room and pillar trial ranged from 700 m to 900 m. It is perhaps the deepest room and pillar coal mining in the world.
