The colliery, as one kind of the mine, is a kind of special geographical area, which is in large scale, wide area, big difference between geological condition and coal seamcomposition.
煤矿作为矿山的一种，是一种特殊的地理区域，规模庞大，面积较广，地质条件和煤层赋存条件差别很大。
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The reasonable definitional feature of shallow coal seam is analyzed base on the overlying strata's composition, the activity law long-wall mining'soverlying layers and the depth of coal seam.
This paper mainly describes the mineral composition, structural behaviour of the weak seam in dam foundation, and its chemically solvent action and variation under long term infiltration of water .