Internal Soil Erosion Involving Concrete Pipes Through Earth Dams

Concrete pipes are often used for principal spillways or low-level drains in earthen embankments of small to medium height. Such pipes can be an avenue for internal erosion (piping) of embankment soils. Internal soil erosion may take place along the exterior surface of concrete and other types of pipes because of poor soil compaction and inadequate seepage control measures. However, what makes concrete pipes unique relative to other types of pipes, is that soil erosion can also take place through the pipe's interior. This type of erosion usually takes place through joints that are improperly sealed or which open because of differential settlement of the foundation materials. Erosion through the inside or along the exterior surface of concrete pipes can lead to significant loss of embankment soil, ultimately causing a breach or severe embankment distress. Three separate case histories are presented to illustrate soil piping problems involving concrete pipes. This paper concludes with a brief overview of design practices presently being used to prevent internal soil erosion in dams containing concrete pipes and some comments about periodic safety inspections of concrete pipes.