METHOD OF WORK:

According to method of mining,coal mines are of two types.Open cast mine and Underground mines.                           Open cast mine:- In opencast method,soil and rock lying over small area of the coal seam is blasted,excavated and dumped on no coal bearing surface nearby.The exposed coal is blasted and mined. Operation of removal of overburden and extraction of coal continue.After coal has been removed over a large area,the over burden is dumped in the trench formed by removal of coal.This is called "backfilling".   Overburden is excavated in steps called benches for reasons of saftey and ease of extraction.Coal seam is also extracted in more than one bench if it is thick.Bench are approached by wide road ways called haul roads, because they are used for transporting or hauling of overburden or coal.   

   Underground mine:-Where the coal seam is situated at a shallow depth,it is reached  from surface by inclines.A deep seated seam is approached by shafts.Whether the seam is approached by inclines or shafts,method of extraction of coal is more or less the same.A roadways in coal seam is called gallery.A gallery driven along the dip is called dip gallery.A gallery driven in a direction opposite to the dip direction,is termed rise gallery.In olden days gallery was called board solid block of coal between galleries is called pillar.Hence the method was called Board and Pillar metohd.