bottom drift meaning in English

海底漂移
下部导坑

Application of caving mining technology with bottom under condition of flat dipping mid - thick body and unstable rock caused the most of trench and bottom drift , located in abutment , to be destroyed and low recovery in south area , xishimen iron mine
摘要在缓倾斜中厚矿体底板岩性不稳固的条件下，采用有底柱崩落法，由于电耙道大多处于空区边部应力集中的部位，致使堑沟及底部结构巷道破坏严重而使回收率极低，采用无底柱崩落卸压则可有效解决上述难题。