Environmental Engineering Reference
In-Depth Information
Figure 15.30.
Winneke Dam foundation treatment (ICOLD, 1989a and Casinader and Watt, 1985). (A)
Upstream toe detail, (B) Concrete face, (C) Anchor bars at 1 m centres longitudinally, (D)
Foundation concrete 0.15 m thick, width 32.25 m, (E) Anchor bars at 2 m centres each
way within thickened section, (F) Overlap 2 m minimum, (G) Fine filter 42-30 m, (H)
Hydraulic head at foundation level, (I) High plinth with buttress. (1) Rockfill, (2)
Transition, (3) Filters, (4) Foundation concrete, (5) Concrete face, (6) Plinth, (7) Anchor
bars, (8) Grout curtain, (9) Foundation, (10), Buttress, (11) Original ground surface.
The measures adopted are described in Casinader and Watt (1985), Casinader and
Stapledon (1979) and Stapledon and Casinader (1977) and included:
-The upstream toe excavation was taken down to the top of the highly weathered rock
zone to reduce the number of infilled seams beneath the plinth;
- Prior to grouting, seams in the grout holes were flushed out as far as practicable using air
and water;
- The plinth width adopted was 0.1 H, or 6 m minimum, where H is the water head -
wider than normally adopted to reduce gradients. The foundation downstream of the
plinth was blanketed with 150 mm of concrete, so that the total width of the plinth and
“foundation concrete” was at least 0.5 H;
-A filter was placed over the foundation for a distance 0.5 H downstream of the foun-
dation concrete and the filter and foundation concrete was covered by the transition
layer to control erosion of fines from the foundation (even if the foundation concrete
cracked).
The possibility of sliding movements on weak seams also necessitated a buttress on the
plinth, as shown in Figure 15.30.
Reece Dam was founded on deeply weathered schists with clay seams at cutoff level on the
left abutment. In this case, the abutment downstream of the plinth was covered with a 150 mm
layer of steel meshed shotcrete for a distance 0.5 H downstream. The whole shotcrete layer,
