Effect of abutment angle on stress distribution under supercritical longwall panels

![CDATA[Efficient and effective ground control design in underground coal mines requires a sound understanding of the stress environment in the surrounding rock strata. This is particularly the case in multiple-seam mining where the stress environment is very different from that encountered when mining in strata that has not previously been mined. This is because previous mining activity causes a redistribution of the ground stresses, leading to the concentration of vertical load in chain pillars. The extra overburden load carried by the chain pillars in longwall mines is related to a quantity identified as the “abutment angle”. This study aims to present the effects of the abutment angle on the final in situ vertical stress in the rock strata underlying supercritical longwall panels. The magnitude and distribution of these vertical stresses provide valuable information when considering multiple seam mine layouts below existing longwall panels. Wilson’s equations have been used for the stress distribution induced in the pillars and longwall goaf, to estimate the stress changes in the strata beneath the mined panel using a plane strain elastic model. Finite element analysis was used to predict the final stress in the underlying strata. The results show that larger abutment angles generate larger stresses in the underlying stratum. For a given ratio of interburden to overburden there is a linear relationship between the abutment angle and the maximum normalised vertical stress.]]