短語詞組短語gassy y seam 瓦斯煤層thick gassy coal seam 含瓦斯厚煤層high gassy coal seam 高瓦斯煤層high gassy seam 高瓦斯煤層gassy seam mining method [礦業(yè)]瓦斯煤層采煤法 返回 gassy seam