Federal Energy Regulatory Commission on Internal Erosion & Piping on Earthen Embankment Dams has one of the best looks at understanding the issue of dam leaking from piping or erosion.
This document demonstrates the complexity of diagnosing problems with earthen embankment dams.
Here is an excerpt. –
“Every dam is unique in its design, construction, operation, and performance. Earth and rock fill dams add a special component to this uniqueness by the complexity resulting from dealing with variable natural materials. As a result, a detailed potential failure modes analysis and the development of specific event trees should be developed for the site specific conditions of the project under review and evaluation. The foundation geology, design, construction methods, monitoring program, and historic performance of the structure affect the development of each detailed potential failure mode and the probability of each node on the event tree to progress to failure, or be stopped prior to progressing to failure. The project characteristics discussed below should be considered during the development of PFMs and the performance of a risk analysis of internal erosion and piping of an earth structure or soil foundation. ”
“Construction Defects. Defects created during embankment construction that lead to internal erosion and piping are usually unknown until the failure mode is initiated. However, understanding how the embankment was constructed and how closely it was monitored during construction can significantly increase or decrease the estimated likelihood of a potential failure mode. Properly identifying and evaluating the risk of these failure modes is extremely challenging.”