Page 299 - Advanced Mine Ventilation

276 Advanced Mine Ventilation

Figure 16.7 Vertical section of a typical gob well.

16.3.2 Location of Gob Wells on the Longwall Panel
The first gob well is usually installed within 50e500 ft from the setup entry. When the
longwall face retreats 100e200 ft, the first main roof fall takes place releasing a large
volume of methane. Sometimes, it is necessary to have two gob wells in parallel near
the setup entry to cope with the onrush of strata gases. Location of other gob wells on
the panel must be done in an optimal manner to capture the maximum percentage of
total gob gas emissions at the minimum cost.
Optimum gob gas drainage depends on the following:

• The size of the gob well and its production capacity.
• Distance of the gob well from the tailgate.
• Spacing of the gob well on the longwall which is a function of the width of the longwall panel
and the rate of mining.