![]() ![]() Relocate underground power, Encased duct bank, includes cable and trenching. If the duct bank is 100 feet, then the total volume of concrete needed is 3.215 square feet times 100 feet, which equals 321.5 cubic feet of concrete. Standard Concrete Encasement, 8- 21 Pipe. Now multiply this number by the total length of the duct bank. ![]() By dividing 462.96 by 144, the result is 3.215 square feet. Finally, divide by 27 to get 300 cubic yards of concrete. Minimum spacing for conduits in multi-duct banks 100-150 mm conduit. Guidance is given for maximum concrete pour depth for classes of pipes in our Technical Note VX-TN-4F. Multiply by1600 to get a total of 8089 cubic feet of concrete. Note that deep pours can generate enough pressure and heat to collapse a PVC duct. Concrete blocks shall be utilized to support the spacers and provide 3' of concrete between the reinforcing steel and the ground. Spacers will be assembled to form the duct bank specified. Divide by 144 to get 5.056 square feet of concrete. Interlocking PVC spacers to provide 1-1/2' spacing between ducts and 3' cover of concrete for the outer ducts, spaced 5 feet on centers will be used. The guideline covers concrete encased duct banks and manholes for primary (medium voltage) power distribution cables and telecommunications cables. That leaves 728 square inches of concrete. This is the cross-sectional area occupied by the concrete alone.Ĭonvert the cross-sectional area occupied by the concrete from square inches to square feet by dividing that number by 144. They will take up 113 square inches of the available area of the square. So, 576-square inches minus 113.04 square inches equals 462.96 square inches. Subtract this number from the total cross sectional area of the duct bank. For a three-by-three, that is 3.14 times 4 times 9, which equals 113.04 square inches. The conduit area is pi times the radius squared times the number of conduits. The conduit area would be the cross-sectional area of one conduit times the number of conduits. Now subtract from this number the total area occupied by the conduit. In this three-by-three example, that would equal 24 inches times 24 inches or 576 square inches. Multiply the total width and total height. If the duct bank is 100 feet, then the total volume of concrete needed is 3.215 square feet times. Since this is a three-by-three duct bank, its height will also be 24 inches.Ĭalculate the cross-sectional area of the duct bank. Now multiply this number by the total length of the duct bank. The work under this section is limited to the assembly of the spacers and ducts required to form the duct bank. Repeat step 2 using the number of vertical conduits instead of the number of horizontal conduits. Calculate the total height of the duct bank. ![]()
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