对埋藏比较浅、延深又比较大的倾斜和急倾斜矿床,往往露天法只开采其上部,下部矿床用地下法去开采。这里,从上下开采的时间关系上有两种干法:一种是上部露天和下部地下开采同时并举,这样,露天开采结束以后,不存在露天向地下开采过渡的问题,只是企业的生产能力有所改变和地下采矿方法可能由充填法改变为高效率的崩落法;另一种是先露天后地下, Of the shallow burial, deep and deep inclined and steep deposits, open-air method is often only the upper part of its exploitation, the lower part of the underground mining method to mining. Here, there are two kinds of dry methods from top to bottom in terms of time: one is that the upper part of the open pit and the lower part of the underground are both in parallel, so there is no problem of transition from the open pit to the underground after the open pit mining is completed. Changes and underground mining methods may be changed from filling method to high-efficiency caving method; the other is underground after open-pit,