Control of seepage, internal erosion and piping for embankment dams - Geotechnical Engineering of Dams - page 427

Table 10.8. Influence of factors on the likelihood of a concentrated leak associated with a spillway wall

(Foster and Fell, 2000).

Influence on likelihood of a concentrated leak

Factor More likely Neutral Less likely

Slope of wall Overhanging Vertical Sloping 0.1 H:1 V

Founding material Soil, wall subject to settlement Soil or weathered rock, Rock

and rotation no rotation

Finish on wall Rough, irregular Smooth, planar

Concrete collars, Present, particularly if shape Not present

buttresses, overhangs makes compaction of core

difficult

Special compaction No special compaction Careful compaction

adjacent to wall adjacent to wall

Figure 10.41. Typical transverse differential settlement cracks (Sherard et al., 1963).

The likelihood of continuation of erosion will be dependent on the compatibility of the
filters and the dam core: If they will:

(a) Seal with no erosion - rapid sealing of the concentrated leak with no potential for
damage and no or only minor increases in leakage, continuation will be very unlikely;
(b) Seal with some erosion - sealing of the concentrated leak but with the potential
for some damage and minor or moderate increases in leakage, continuation will be
likely;
(c) Excessive or continuing erosion - slow or no sealing of the concentrated leak with the
potential for large or continuing erosion losses and large increases in leakage, continuation
will be highly likely.