• 煤层直接之间极易垮落软弱岩层井下采煤工作面回采时,常常遇到

    The false top is the existence pole exchanges weak caving rock stratum between the coal seam and direct top. In the coal mining, it may often be happened.

    youdao

  • 煤层直接之间极易垮落软弱岩层井下采煤工作面回采时,常常遇到

    The false top is the existence pole exchanges weak caving rock stratum between the coal seam and direct top. In the coal mining, it may often be happened.

    youdao

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