不稳定顶板 meaning in English

weak roof

Bolt - mesh - beam support technology used in instable roof seam roadway
破碎不稳定顶板煤巷锚网梁支护技术
Research and application of working face unstable roof treatment technique
采煤工作面不稳定顶板治理技术的研究与应用
Practices on bolt , mesh , anchor and beam support in coal drift under unstable roof condition of cataclastic rock mass
不稳定顶板煤巷锚网索梁支护实践