Question:
A Bord and Pillar panel is developed at a depth of 250 m in a flat coal seam. The vertical stress gradient is 0.027 MPa/m. If the strength of a square pillar is 12.5 MPa, the extraction ratio of the pillar for a safety factor of 1.5, is____.(round off up to 2 decimals)
A Bord and Pillar panel is developed at a depth of 250 m in a flat coal seam. The vertical stress gradient is 0.027 MPa/m. If the strength of a square pillar is 12.5 MPa, the extraction ratio of the pillar for a safety factor of 1.5, is____.(round off up to 2 decimals)
Updated On: Sep 9, 2025
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Correct Answer: 0.18
Solution and Explanation
The correct answer is: 0.18 or 0.20 (approx)
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