Strata behavior in extra-thick coal seam mining with upward slicing backfilling technology

Based on the character of upward slicing backfilling mining and the condition of Gonggeyingzi coal mine in Inner Mongolia, this paper describes the studies of the strata behavior and the stress distribution in the process of backfilling mining in extra-thick coal seams. This was achieved by setting up and analyzing the elastic foundation beam model using the ABAQUS software. The results show that: (1) With the gradual mining of different slices, the roof appears to bend continuously but does not break. The vertical stress in the roof decreases and the decreasing amplitude reduces, while the tensile stress in the roof grows with the mining slices and the maximum tensile stress will not exceed the allowable tensile stress. (2) The front vertical stress at the working face exceeds the rear vertical stress and both show a trend of decrease with decreasing amplitude of decrease. (3) The slices mined early have more influence on the surrounding rock than the later ones. Similarly, the strata behavior experiences the same trend. The field measured data show that the roof does not break during the mining process, which is consistent with the conclusion.