ABSTRACT
Backward erosion piping can occur when an unfiltered exit is present on the downstream side of a levee and seepage forces are sufficient to transport sand grains. A pipe forms, which progresses upstream, in the opposite direction of flow, below the levee. Small-scale model tests have shown that a coarse sand barrier can be effective to prevent piping. This paper describes some of these tests. These tests are part of a research programme that also includes medium-scale, large-scale tests and numerical calculations. The small-scale tests confirm that the coarse sand barrier is very effective at this scale and offers possibilities for prediction at larger scale. This paper describes some practical issues related to the physical modeling of the barrier and how these affect the results. In addition, scale effects are discussed.
