In underground coal mines, please give explanation impact of these parameters on roof fall in different mining methods like Bord and pillar and Longwall.
Area of exposure encompasses total area, i.e., area of exposed roof, floor and sides. On the other hand area of roof exposure implies the exposed roof span only. As such, the area of roof exposure is almost same as area of floor exposure. However, area of total exposure may be different for same exposure area of roof, depending on the height of sidewalls of excavation. Area of roof exposure is critical and greatly affects the susceptibility to roof falls. It should be well supported with proper type of supporting scheme, or else, beyond the critical span of roof exposure, the immediate roof ought to fall unprecedentedly. Likewise, total area of exposure is also critical to the stability of entire excavation. Too high area of exposure may lead to spalling of sides, failure of pillars and even collapse or destabilization of entire excavation.
Area of exposure gives a volumetric sense and area of roof exposure gives a geometric sense.
it means any place or point which is exposed to the under ground environment is included in area of exposure and area of roof exposure is also an exposed area but restrict only upto the roof.
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