Years before, men had dug the mine shaft straight back into the mountain.

几年前，人们开挖这个笔直地退进山里的这个矿井。

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Shaft seal is adapted, which can bear higher back pressure.

采用进口轴密封，能承受高背压。

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Shaft seal is adapted, which can bear higher back pressure.

采用进口轴密封，能承受高背压。

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