Environmental Engineering Reference
In-Depth Information
Figure 15.7.
Salvajina Dam (Sierra et al., 1985, reproduced with permission of ASCE).
Figure 15.8
. There was little difference in grading between the zones II, III and IV. The dam
failed when leakage occurred through joints in the face, particularly at the join of the face
slab and the wave wall which was below the reservoir normal FSL. The relatively fine fill,
with no higher permeability zones as are built in to other gravel fill dams, contributed to
the failure.
Figure 15.9(a)
and (b) show the failed dam and Figure 15.9(c) the crest wall detail.
15.2.3
Effect of rock properties and compaction on modulus of rockfill
The modulus of compressibility (E) of the rockfill is dependent on the rock type, strength,
shape and gradation of rock sizes in the rockfill and layer thickness. It is also dependent on the
roller size and type, number of passes, whether water is added during compaction, the confin-
ing stresses on the rockfill and also the duration of loading, i.e. there is a creep component.
Table 15.6
summarizes the properties of compacted rockfill from a number of CFRDs.
The rockfill moduli during construction (E
rc
) and the pseudo modulus on first filling (E
rf
)
values have been calculated from observed settlements of rockfill during construction of
the dam using cross-arm settlement gauges and from the observed deflection of the face
slab on first filling. Unless otherwise stated, the values quoted are generally “average”,
typical of rockfill at the lower half and centre of the dam. The moduli have been calcu-
distributions due to the shape of the embankment have been allowed for, using elastic
solutions in Poulos and Davis (1974).
Fitzpatrick et al. (1985) calculate E
rc
and E
rf
from
(15.1)
E
d /
rc
1
s
Ehd /
rf
(15.2)
2
n
