medium thickness seam 中厚层

thin and medium seam 薄及中厚煤层

medium-thick seam 中厚煤层

medium thick seam 中厚煤层

medium-steep seam 中倾斜矿层

medium-thickness coal seam [矿业] 中厚煤层

medium-thickness seam mining method [矿业] 中厚煤层采煤法

medium m thickness seam 中厚层

medium soft seam 中软煤层