Section 111(2) in The Coal Mines Regulations, 2011
(2)The slope of a spoil bank shall be determined by the natural angle of repose of the material being deposited but shall not exceed 37.5 degree from the horizontal:Provided that if scientific studies indicate possibility of information of steeper slope of a spoil bank, approval of such slope angle subject to the conditions specified shall be obtained from the Regional Inspectors.
