Table 1: Potential for surfacing internal erosion in glacial moraine core embankment damsKenny & Lau[1] (1985, 1986)Max filter Unstable core/Unstable core Stable core/

1. Internally unstable if H/F < 1, internally stable if H/F ≥ 1
2. Always high potential if DF15 > 9 DB95 regardless of internal stability. Foster & Fell (2001) continuing erosion boundary. Re-grade core soil on the 4.75mm sieve.
3. Sherard and Dunnigan (1989) no erosion boundary (soil group 2 base soils).

D15 (mm) unstable filter and stable filter stable filter
or stable core and
unstable filter
≥ 1.42 High2 Increased Neutral
>0.7, <1.4 Increased Neutral Reduced
≤0.73 Neutral Reduced Low