virgin coal的用法和樣例：
例句
- Medium and small coal mines in north of Shaanxi Province generally adopt longwall remaining coal pillars support mining.
摘要長(cháng)壁留煤柱支撐法開(kāi)采是陜北中小煤礦普遍采用的一種采煤方法。 - The coal pillar has mode-soft behaviour, so it is possible to estimate the destabilization.
煤柱失穩還具有模態(tài)軟化特性，可以對失穩的可能性進(jìn)行佑計。
