Face length is not too large, and appropriate to reduce the face length, on the one hand, to speed up the advancing degree, on the other hand can reduce the face at both ends of the wind pressure, reduce the work for the of Gob oxygen.

Surface length must not be too large, reduce surface appropriate length, on the one hand to be able to accelerate on the one hand, you can reduce surface damaged from wind pressure difference between two end-to-face to reduce air leakage empty oxygen.

The working surface length cannot oversized, reduces the working surface length suitably, on the one hand can speed up pushes the progress, on the other hand may reduce the working surface both sides leeway, reduces the work face to pick the depletion region to leak out for the oxygen.

Face cannot be too large, appropriately reduce the length face, to speed up on the one hand, the other hand reduces the working face wind pressure at both ends, reduced air leakage in goaf of working face for oxygen.

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