Experimental Study on Energy Evolution and Failure Characteristics of Rock–Coal–Rock Combination with Different Height Ratios

Abstract

Compared with the surrounding rock of single rock roadway, the uneven deformation of surrounding rock of thin coal seam roadway is more prominent. This uneven deformation characteristic of thin coal seam surrounding rock between the different surrounding rocks has greatly hindered the mining of thin seam coal mines. Based on the uniaxial loading tests and uniaxial cyclic loading tests of the coal–rock combination, the deformation characteristics and loading failure of coal–rock combination with different height ratios of coal to rock is studied. The results show that the uniaxial compression strength of coal–rock combinations increases with coal height. By comparing and analyzing the energy evolution of the composite with different height ratio, the energy dissipation of the coal–rock combination decreases suddenly between RCR-0.5 and RCR-1 specimens. The coal body is constrained by the sandstone at both ends of the composite specimen, which improved the strength of the coal body. The effect of this constraint decreases with the distance from the coal–rock interface. The failure mode of the composite specimens is dominated by the coal body, which is from splitting failure to shear failure finally becomes middle coal extrusion.