coal ncrushing nmachine nin nchina nand nsingapore
batu ncrushing nplant nbusiness nplan nin nindia coal crusher business plan batu coal crusher business plan A. Abutment In coal mining, (1) the weight of the rocks above a narrow roadway is transferred to the solid coal along the sides, which act as abutments of the arch of strata spanning the roadway; and (2) the weight of the rocks over a longwall face is transferred to the front ...