There's a thin layer of coal between the two layers of rock.
在这两层岩石之间有一薄层煤。
A thin layer or stratum, as of coal or rock.
薄薄的一层或层面，如煤或岩石的。
Therefore, it is necessary to accurately know the position of coal layer and its parameters.
因此，准确地掌握煤层位置和有关参数是十分必要的。
Therefore, it is necessary to accurately know the position of coal layer and its parameters.
因此，准确地掌握煤层位置和有关参数是十分必要的。
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