An electrical contractor is preparing to place the duct bank concrete encasement for the high voltage feeders between manhole # 11 and # 12, total distance is 323-ft. The duct bank is 2-ft x 3-ft and holds nine 4.5-in Schedule 80 PVC conduits. The amount of concrete to be ordered is most nearly:
Solution:
Nominal 4-in Schedule 80 PVC pipe is 4.5-in O.D.
Total Volume = 2' x 3' x 323' = 1938-ft^{3} / 27-ft^{3}/CY = 71.77-yd^{3}
Total Deduct = 9 x (π ((4.5"/12")/ft)^{2})/4 x 323' = 321-ft^{3} / 27-ft^{3}/CY = 11.89-yd^{3}
Total Concrete = 71.77-yd^{3} - 11.89-yd^{3} = 59.88-yds^{3}