(b) Downstream supporting shoulder
A supporting shoulder can be constructed, as shown in Fig. 3.11, employ-
ing compacted earthfill or rockfill. Support is provided from the positive
contribution to stability made by the weight of fill above the downstream
face,WF. A further contribution is made by the horizontal ‘at rest’ pres-
sure,Pds, generated on plane AB.
WF (areaA)(kNm^1 ) (3.42)
and may be considered to act through the centroid of the fill profile of area
Aabove the toe, and
PdsK 0 zABZ(kN m^1 ) (3.43)
whereK 0 is the ‘at rest’, or zero lateral strain, pressure coefficient and zAB
andZare defined as in Fig. 3.11. Pdsis considered to act at height zAB/3
above the base plane. Illustrative values for K 0 are shown in Table 3.9.
154 CONCRETE DAM ENGINEERING
Fig. 3.11 Stabilizing: construction of downstream supporting shoulder
Table 3.9 Illustrative values for coefficient, K 0
Shoulder fill Coefficient, K 0
Compacted rockfill 0.30–0.60
Compacted sand 0.45–0.60
Compacted clay 1.00–1.50
Heavily compacted clay 1.50
