Environmental Engineering Reference
In-Depth Information
Figure 15.32.
Grouting and drainage gallery, Aquamilpa Dam (Moreno, 1987, reproduced with per-
mission of ASCE).
Cooke and Sherard (1987) point out that these zones were first used on the lower part
of Alto Anchicaya Dam, because at that time the dam height was breaking precedents.
The detail has since been repeated on Foz do Areia Dam (Pinto et al., 1985); Khao Laem
Dam (Watakeekul et al., 1985); Golillas Dam (Amaya and Marulanda, 1985). The
designs for recent dams in Colombia (Amaya and Marulanda, 2000) and Brazil (Sobrinho
et al., 2000) include upstream protection of the lower section of the face slab.
The concept is to cover the perimetric joint and plinth in the lower elevations with
impervious soil, which would seal any cracks or joint openings. Zone 1A is a minimum
practical construction width, with Zone 1B provided for stability.
As pointed out by Cooke and Sherard (1987) many dams have been successfully con-
structed without this upstream zone, and if Zone 2D is graded fine to act as a filter to
dirty fine sand in the event of leakage, there seems little justification for the fill in most
dams. They do seem, however, to favour its application in the lower part of the plinth in
high dams.
15.5.5
Spillway over the dam crest
Cooke and Sherard (1987) discuss the concept of building the spillway on the down-
stream face of a CFRD. They suggest that it is practical for ungated moderate size spill-
ways with a peak discharge of around 25-30 m 3 /sec per metre of chute width, and where
flood flows are of short duration. They suggest the following principles:
- The whole of the rockfill should be compacted to Zone 3A standard to limit settle-
ments;
-A layer of fine rock should be placed under the concrete, as for the face slab, and this
should be rolled to make it a good even and stiff support for the concrete slab in the
spillway;
 
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