Because the first caving of work face haven't been finished, the tunnel roof and hole can not be used and gas often goes beyond the limit, so some measures must be taken.
由于工作面初次放顶没有完成，顶板巷道、顶板钻孔等不能发挥作用，常发生瓦斯超限现象，必须采取针对性措施。
It was the first time that full-mechanized caving mining was used under sea in the history of coal mining under sea in the world.
海域下煤层采用综放开采在世界海域煤炭开采史上还是首次。
As the first successful introduction of natural caving method in domestic nonferrous metal mine, Tongkuangyu mine increases production capacity and reduces production costs.
铜矿峪矿作为国内第一个成功引进自然崩落法技术的有色金属矿山，提高了矿山生产能力，降低了生产成本。
The block which will be the first of caving rocks from free surface and lead to more caving or side-fall in underground work is known as "critical rock".
地下工程中临空面上首先冒落并引发其他岩块冒落或片帮的块体称作“危石”。
The block which will be the first of caving rocks from free surface and lead to more caving or side-fall in underground work is known as "critical rock".
地下工程中临空面上首先冒落并引发其他岩块冒落或片帮的块体称作“危石”。
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