Section 109(2) in The Coal Mines Regulations, 2011
(2)The height of the benches in overburden consisting of alluvium or other soft soil shall not exceed 3 metres and the width thereof shall not be less than three times the height of the bench and the height of the benches in overburden of other rock formation shall not be more than the designed reach of the excavation machine in use for digging, excavation or removal.
