Flexible and Rigid Pipe Installation:
Review and Discussion
Flexible pipes respond to load differently than rigid pipes as shown in the picture to the right. Flexible pipe require a very strong, well compacted side fill, because the pipe will shorten vertically with applied vertical load thereby deflecting the sides of the pipe outward horizontally engaging the side-fill soils as a column that is assumed to be stiffer than the pipe and carries some of the vertical load; and as a bearing surface for the sides of the pipe to resist the horizontal deflection of the pipe counteracting the deflecting forces within the pipe. Rigid pipe deflects vertically, but to a much lesser degree and relies very little on the horizontal support given by the side-fill soils.