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coal crusher balls material specifiion Roadheader. Glossary of Mining Terms Coal Eduion. 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 abutment, that is ...