Estimate the production of a non-propelled mechanical clamshell dredge using non

Question

Estimate the production of a non-propelled mechanical clamshell dredge using non-propelled hopper barges (scows). The bucket size is 4 cubic meters. The material to be excavated is a mixture of sand, clay, and gravel that has a bulking factor of 1.25. The dredging depth is 10 m and the area to be dredged is 558 m2 . Non-propelled hopper barges (scows) with a capacity of 300 cubic meters are used. The time to change hoppers is 10 min and the advance time is 2.5 min. The thickness of the cut is 0.5 m. Assume the delay factor is 0.87, the mechanical delay factor is 0.85, and the operational factor is 0.9.

Explanation / Answer

Given data:

Bucket size ( C ) = 4 m3

Bulking factor (B) = 1.25

Dredging depth (z) = 10m

Area to be dredged (A) = 558 m2

Capacity of Scows (H ) = 300 m3

Time to change hopper ( th ) = 10 min

Advance time (Ta ) = 2.5 min

Delay factor ( fa ) = .87

As given by Bray;

fa = 1/(1+(ta Pnom B/Az))        where Pnom = Nominal production

After putting the values in the above equation and calculating

Pnom = 4.45 m3/hr

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