unstable roof的意思|示意

The results of numerical analysis on mined-out area indicate that the roof at mined-out areas is unstable and the rock in the roof is easy to collapse in this mine.

数值分析结果表明：夹沟矿采空区的顶板是不稳定的，顶板岩体容易发生垮落事故。

Mining of gently inclined thin and medium thick ore body with unstable roof isregarded as typical hard-to-mine ore body.

顶板不稳定的缓倾斜薄、中厚矿体为典型的难采矿体。

Part of ore body in Jinchangyu Gold mine is this kind of gently inclined thin and medium thick ore body with unstable roof, it is hard to mine.

金厂峪金矿部分顶板不稳定的缓倾斜薄至中厚矿体，其开采难度很大。