Mining-induced stress changes and rock burst control in a variable-thickness coal seam

In longwall mining, one of the factors most influencing safety in underground coal mining is the stress change, especially when such work is carried out within the thickness variation of a coal seam. This paper analyses the special case of a coal seam which suffers significant overstress as a result of variations in the geometry and dimension of the load itself, in particular, thinning. This is because such thickening and thinning locations of the thickness are generally areas where rock bursts occur most frequently. The results of the research were validated by measuring the stress state in the area under study. A numerical model was established using FLAC(3D) to understand the results of the field tests and map the zones in the model with a high risk of rock burst. The results of field tests, and the numerical modelling, show that thinning accentuates the stress concentration and energy accumulation. Furthermore, on the basis of a retrospective analysis of what was observed in a coal mine, some preventative measures were instigated as rock burst controls. Also, it was found that rock burst occurrence can be effectively reduced by the use of large-diameter drilling and break-tip blasting.