When the required pipe strength exceeds a D-load of 3000 lb./ft./ft. (140 N/m/mm), the structural design of the pipe can fall into a special design category. This can increase the cost because such pipe is usually not a standard stock item with the manufacturer.

Often, refinement of parameters for high-strength pipe, such as bedding, soil weight, and/or trench width, is warranted because the cost of stronger pipe justifies a more refined analysis. For such cases, even the use of Class A bedding may prove to be cost-effective.

Contact the concrete pipe manufacturer for assistance with estimates for the various design alternatives when earth loads require pipe strength greater than 3000 lb./ft./ft. (140 N/m/mm).