Geomechanics and Ground Control · Ground Control · 2 marks · Multiple choice
Longwall shields have yield capacity 460 tonnes each, canopy length 3.25 m and width 1.5 m, and setting capacity 80% of yield. Tip-to-face distance after full advance is 0.15 m; web depth 0.60 m. Shields are skin-to-skin. Find setting resistance at maximum and minimum face spans, in t/m².
Setting load is 0.8×460=368 t. Maximum supported span is 3.25+0.15+0.60=4.00 m, giving 368/(4×1.5)=61.33 t/m². Minimum span is 3.40 m, giving 368/(3.4×1.5)=72.16 t/m², matching A’s rounded pair. Use setting rather than yield load.
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