retreating mining meaning in English

后退式开采

The coal was being mined by a method called “ retreat mining ”
这个煤矿的开采方式被称为“撤退式开采” 。
Robert murray , the mine ' s owner , says that “ retreat mining ” was not being used in crandall canyon
矿主罗伯特默里说克兰德尔峡谷煤矿并没有采用这种“撤退式采矿”方法。
Records show , however , that the mining plan recommended by an engineering firm and approved in april by the federal govern - ment , was for “ retreat mining
然而拒资料显示，一个工程公司向他们推荐的采矿计划，并且在四月份得到联邦政府批准的就是“撤退式采矿”方法。