Concrete Pipe & Box Culvert Installation - Shaw Precast Solutions

For those projects still using the older beddingtypes, bedding types, A, B, C and D are presented.CLASS A BEDDINGCONCRETE CRADLECONCRETE CRADLE – Used only with circularpipe, the pipe is bedded in non-reinforced or reinforcedconcrete having a thickness, d, as listed,and extending up the sides for a height equal to theoutside diameter. The cradle should have a minimumwidth at least equal to the outside diameterof the pipe plus 8 in. (200 mm). The backfill abovethe cradle is densely compacted and extends 12in. (300 mm) above the crown of the pipe. In rock,especially where blasting is likely in the adjacentvicinity, the concrete cradle should be cushionedfrom the shock of the blasting which can be transmittedthrough the rock.CLASS B BEDDINGSHAPED OR UNSHAPEDGRANULAR FOUNDATIONSHAPED – For a shaped subgrade with granularfoundation, the bottom of the excavation is shapedto conform to the pipe surface but at least 2 in. (50mm) greater than the outside dimensions of thepipe. The width should be sufficient to allow 6/10of the outside pipe diameter for circular pipe, 7/10of the outside span for arch and elliptical pipe, andthe full bottom width of box sections to be beddedin fine granular fill placed in the shaped excavation.Densely compacted backfill should be placed at thesides of the pipe to a depth of at least 12 in. (300mm) above the top of the pipe.American Concrete Pipe Association • www.concrete-pipe.org 27