There are four layer coal in Huafeng coal mine of Xinwen coal group company, it is mined layer by layer, artificial roof is used by diamond metal net over a long period of time.

新汶矿业集团华丰煤矿四层煤分层开采，长期以来全部采用金属菱形网作假顶。

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There are four layer coal in Huafeng coal mine of Xinwen coal group company, it is mined layer by layer, artificial roof is used by diamond metal net over a long period of time.

新汶矿业集团华丰煤矿四层煤分层开采，长期以来全部采用金属菱形网作假顶。

youdao