Page 306 - Advanced Mine Ventilation

Floor Gas Emissions and Gas 17

Outbursts

Chapter Outline

17.1 Floor Gas Emissions 284
17.1.1 Premining Methane Drainage 284
17.1.1.1 Hydrofracturing of Underlying Coal Seams 285
17.1.1.2 Horizontal Boreholes Drilled from Surface 286
17.1.2 Postmining Methane Drainage 287
17.1.2.1 Cross-Measure Boreholes in the Floor 287
17.1.2.2 Vertical Gob Wells Completed in Lower Coal Seams 288
17.1.3 Injection Boreholes on Longwall Faces 289
17.2 Gas Outbursts 289
17.3 Parameters Indicating a Propensity to Gas Outbursts 290
17.3.1 Australia 291
17.3.2 China 291
17.3.3 Kazakhstan 291
17.3.4 Ukraine 292
17.4 Prevention of Gas Outburst 292
17.4.1 Moderately Gassy Coal Seams (Depth 600e1500 ft) 292
17.4.2 Highly Gassy Coal Seams (Depth 1500e3000 ft) 293
17.4.3 Highly Gassy Coal Seams Deeper than 3000 ft 293
17.4.3.1 Horizontal Drilling from the Surface 293
17.4.3.2 Drilling Procedure 294
17.4.3.3 Hydrofracking of the Lateral 296
References 296

In Chapters 15 and 16 of the book, the premining degasification and the postmining
degasification of coal mines were discussed in a generic form. Two special cases
need a separate and comprehensive discussion. They are as follows:

• Floor gas emissions and
• Gas outbursts.
As discussed in Chapter 16, longwall mining makes the mine floor heave. If there
are coal seams in the floor overlain by a strong sandstone or shale, they cannot emit the
released gas to the gob emission spaces, until the said overlying strata breaks suddenly
releasing a large volume of gas and coal fines into the mine. The volume of gas is so
large that it reverses ventilation on the longwall face and explosive mixtures of air and
methane flood into the intake airways with nonpermissible equipment. Consequently,
a mine explosion occurs costing many human lives. Techniques to avoid this disaster
will be discussed here.

Advanced Mine Ventilation. https://doi.org/10.1016/B978-0-08-100457-9.00017-1
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