Question:
The CORRECT curve showing the relationship between vertical stress on a coal pillar and extraction ratio of a bord and pillar panel in a horizontal seam is
The CORRECT curve showing the relationship between vertical stress on a coal pillar and extraction ratio of a bord and pillar panel in a horizontal seam is
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Pillar stress always increases with extraction ratio—never decreases—because fewer pillars must carry the same overburden load.
Updated On: Dec 26, 2025
- Curve A.
- Curve B.
- Curve C.
- Curve D.
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The Correct Option is C
Solution and Explanation
In bord and pillar mining, as the extraction ratio increases, the load transferred to the remaining pillars increases.
Step 1: At low extraction ratios, the pillar stress increases slowly because plenty of pillars share the load.
Step 2: As extraction continues, pillar area reduces, causing a faster increase in load concentration.
Step 3: The curve should therefore show a non-linear increasing trend without sudden drops or negative slope.
Curve A rises too steeply, B rises linearly, D decreases (which is impossible).
Curve C shows the correct gradual non-linear increase in pillar stress with extraction ratio.
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