Numerical investigation into impacts of major fault on coal burst in longwall mining – A case study

Abstract

The presence of geological faults is a significant contributing factor to coal burst in underground mining. In this study, a large-scale discontinuum model was established based on geological and geotechnical conditions in a mine site, where a longwall face passed through a major fault. Four model indicators were calculated during the longwall retreat: model seismic energy (energy released by the model system), fault seismic energy (energy released by fault-slip only), peak abutment stress and maximum strain energy density in coal seam. The change pattern of model seismic energy in the discontinuum model was calibrated against the seismic energy recorded in the mine site. It aims to verify that the model seismic energy can properly demonstrate the seismic energy observed in practice. The model results showed that the peak abutment stress and maximum strain energy density in coal seam increased when the longwall face approached the major fault, and then both of them experienced a most significant reduction when the largest fault-slip event occurred. A coal burst risk classification was then developed using multiple model indicators for the case study. A parametric study was conducted based on the calibrated model, which aims to investigate the impacts of various conditions on both fault-slip behaviour and stress and strain energy distributions around longwall excavations. Four factors were studied: the static friction angle of fault, the cover depth of fault, the dip angle of the coal seam and the mining direction. This study and the proposed model indicators can provide an improved understanding of fault-slip burst mechanisms and insights into the associated coal burst proneness assessment.