Local Experimental Approach to the Progression of Backward Erosion Piping

ABSTRACT

Backward erosion threatens the safety of dams as it forms a pipe in the dam foundation that extends from downstream to upstream. Extensive research has been conducted to analyze the progression of this pipe using a global approach, leading to the establishment of criteria in terms of a critical global gradient. The complex conditions existing in the field such as heterogeneity may present difficulties when applying these global criteria. This study provides more experimental data in the vicinity of the progressing pipe tip in conditions where the pipe is free to progress in any directions using a rectangular setup equipped with rows of pressure sensors along the erosion pathway. Pressure variation around sensors was analyzed to investigate the influence of distance on the measured local gradient. The proposed approach proved successful, and it was shown that as the measurement distance decreases, the local gradient increases. The local gradients obtained for shorter distances in this study correspond well to the data found in the literature. Furthermore, a modified secant function was proposed to predict critical local gradients close to the pipe tip. The evaluation of this modified secant function using data from the present study as well as previously published data shows promising results.