When a pipe culvert is constructed on or near the natural ground surface and covered by a highway fill or embankment, the weight of the embankment compresses and consolidates the foundation soil, settlement occurs, and the culvert subsides or sags below the original line as illustrated in Fig. 1. The amount of settlement depends, of course, upon the fill height or load, the depth of foundation soil, and the susceptibility of the foundation soil to consolidation. In addition, and toward the toes of the embankment, the structure may tend to lengthen. It may lengthen slightly, however, simply because the distance along the sag or the settlement curve is greater than the straight grade distance. These movements are damaging to the drainage structure and should be minimized or otherwise compensated in design insofar as practicable.

Report Date


Report Number

No. 145

Digital Object Identifier