Investigation of pillar failure in the Emaswati Coal Mine, Swaziland

The causes and mechanisms of pillar failure in a section at the Emaswati Coal Mine in Swaziland are discussed. The study indicates that there exists an intricate relationship between the local geology and ground instability that needs to be addressed if future pillar failure is to be avoided. The conclusions are mainly based on extensive in-mine investigations and finite element computer modeling using the mechanical properties of mine roof, coal, and floor. The study has indicated that pre-mining failure, coupled with the possible loss of strength due to the heating of the coal seam (which was caused by the hydrostatic emplacement of dolerite dykes and sills) adversely affected the bearing capacity of subsequent coal pillars.