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Author: Admin | 2025-04-28
The heavier material to settle, the light stuff passing with the water to the river. A retaining wall of scrub is built up as the dump rises.The duty of the water, or, in other words, the number of gallons required per cubic yard removed depends on the following conditions :—Nature of the material being dealt with.Quantity of water used (within limits).Pressure of the water.Design and grade of tail-races.Ease of getting material into race.Care and attention on the part of nozzleman and rakers.The actual quantity removed annually is over half a million cubic yards. In one year 198,162 cubic yards were removed from one hill, the water used being = 7,509 sluice-head days. The duty is therefore 8,184 gallons per cubic yard. Another way of expressing the same result is 26.39 cubic yards removed per sluice-head per day.In another face 321,100 cubic yards were shifted, the water being equivalent to 11,630 sluice-head days, giving a duty of 27.61 cubic yards per sluice-head per day. In the latter case some of the water used was at a greater pressure than in the former. The mean of these results is27.00 cubic yards per sluice-head per day on a tail-race grade of 1 ft. 9 in. per chain.The grade must always be stated, the amount of overburden removed being directly proportional to the steepness of the tail-race.If the fall be. 1 ft. in 6 ft., then the ratio of overburden to water in the tail-race is 1 : G (nearly). In the above case the grade of 1 ft. 9 in. per chain (1¾ in 66) is equal to 1 in 37.7, so, theoretically, 37.7 parts of water would remove 1 part of basalt.1 sluice-head = 24 cubic feet of water per min.= 1,280 cubic yards per day.So on the above grade the theoretical
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