Figure 8  | Scientific Reports

Figure 8 

From: Research on controlling gas overrun in a working face based on gob-side entry retaining by utilizing ventilation type “Y”

Figure 8 

The cloud map distribution of goaf gas concentration is presented when the different diameters of the borehole are used. Figure 8 illustrates the cloud map of the gas concentration distribution in the deeper goaf under the different diameters of the borehole. To further resolve the problem of the higher gas concentration in the deeper goaf, the gas concentration in the goaf is simulated when the diameter and the depth of the buried pipe are 400 mm and 4.0 m, respectively, and the high-level borehole is carried out in the deeper goaf. When the diameter of the borehole is 120 mm, the gas concentration decreases most obviously. The maximum gas concentration in the deeper goaf decreases to 3.52%. The gas concentration in the upper corner is further decreased to 0.21%, ensuring the working face’s safe production.

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