Assessing embankment dam filters that do not satisfy design criteria

A method is presented for assessing the particle size distribution of the filters in a dam compared to the soil the filter is protecting, to determine whether the filters are sufficiently fine to give no, excessive, or continuing erosion. The method is based on the analysis of the results of laboratory tests and the characteristics of dams that have experienced piping incidents. The method can be used to determine whether filters that are coarser than required by modern filter design criteria will eventually seal or experience continuing erosion leading to possible failure of the dam in the event piping initiates.