Minimum Cover Requirements for Reinforced Concrete Pipe

Reinforced concrete pipe is a strong pipe with the ability to resist most any loads. It is used for culverts, storm drains and similar projects, The compressive strength for concrete generally ranges from 4,000 pounds per square inch — psi — to 8,000 psi. Concrete pipes do not require the same amount of cover as plastic pipe, but there are maximum cover depths for concrete.

Construction Uses

If the complete pipe installation will have construction equipment traveling over it, the minimum backfill cover should be 3 feet over the section. If the pipe is installed in an embankment and has construction traffic over it, the backfill should be one section span or 3 feet, whichever is larger. This should extend in each direction around the pipe to minimize lateral displacement.

Enbankment Bedding

Circular pipes in an embankment should be covered at different depths, depending on the bedding material. The measurement for backfill cover begins at the center of the pipe, above the bedding material. For a concrete cradle, the minimum cover should equal the outside diameter of the pipe plus 8 inches. For a compacted granular foundation, the minimum depth is one and a quarter times the diameter of the pipe.

Trench Bedding

For circular pipe in a trench, the minimum depth of backfill should be one and a fourth times the diameter of the pipe from the top of a concrete cradle, with at least 12 inches above the top of the pipe. For a granular foundation, the backfill should be at least 12 inches over the top of the pipe, and for a flat subgrade with a class D bedding, there should be at least 6 inches of loose backfill over a pipe.

Maximums

The maximim height of fill over reinforced concrete culverts is about 6 meters for class three pipe, 9 meters for class four pipe, and 15 meters for class five pipe. These numbers apply to installation in an aggregate bases. In different beds, the maximum depths allowed are lower.