Mining Engineering > GATE 2018 > Underground Coal Mining
A coal seam lying at a depth of 200 m is developed by bord and pillar method. Pillars are 30 m centre to centre with a gallery width of 4 m. Unit weight of the overlying strata is 28 kN/m3 If the pillar strength is 9.32 MPa, the factor of safety of pillar is ___________.
Correct : 1.2
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