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一、地面垂直钻孔预抽煤层瓦斯1950年美国就在东部匹兹堡煤层进行了地面垂直钻孔预抽煤层瓦斯的试验。图1是20个地面钻孔(孔间距为450米)总瓦斯流
First, the ground vertical borehole pre-pumping coal seam In 1950 the United States in the eastern Pittsburgh coal seam on the ground vertical drilling pre-pumping seam gas test. Figure 1 shows the total gas flow for 20 ground drills (450 m holes)