Practice on trial mining in special thick seam with soft roof, soft coal, soft floor, high inclination, rich water and high gass under nappe是什么意思_Practice on trial mining in special thick seam with soft roof, soft coal, soft floor, high inclination, rich water and high gass under nappe在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句