GATE 2024 MN – Question 64
A continuous miner cuts a 5×3 m face with 0.6 m web, one full-height web each 9 min. Two shuttle cars each hold 10 tonnes at fill factor 0.9 and have 6 min full cycles. Coal density 1.4 tonne/m³, swell factor 1.2, working shift 6 h. Find nonworking minutes per car needed to carry all cut coal, to two decimals.
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Correct answer: 150.00 to 160.00
Explanation
The shift has 360/9=40 webs. Using the source’s swell-adjusted transport convention, total dispatched quantity is 40×5×3×0.6×1.4×1.2=604.8 tonnes. At 9 tonnes per trip, the two cars share 67.2 trips, or 33.6 each. Each works 33.6×6=201.6 min, leaving 158.4 min. This convention treats the supplied 1.4 value with the loose-volume adjustment; true mass conservation with in-situ density would omit the swell multiplier.