Environmental Engineering Reference
In-Depth Information
Figure 2.38.
Features exposed in trenches on a left bank dipslope at Sugarloaf Dam.
Figure 2.39.
Sugarloaf Dam, cross section through left abutment ridge section.
past undercutting by erosion had apparently provided freedom for the slope movements
to occur.
Laboratory direct shear tests showed the weathered bedding surface seams to have
effective residual strengths of about 10°. The residual value was adopted in stability
analyses because the seams were initially near-planar faults and the small displacements
during slope movements would have been enough to reduce their strength to this value.
The combination of very low strength dispersive seams and dipslopes provided interesting
design questions which are discussed in Casinader and Stapledon (1979).
Figure 2.39 shows the arrangement adopted for the section of the dam on the left bank
ridge. The plinth was located close to the crest of the ridge, to minimise loading of the dip-
slope. This resulted in much of the embankment being located on the downstream side of
the ridge. The dipslope was stabilised by covering it, and filling the gully upstream from
it, with waste material from a nearby excavation.
 
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