Environmental Engineering Reference
In-Depth Information
Figure 11.9.
Cone Resistance q
c
determined from Cone Penetrating test, versus depth below dam crest
for eppalock dam (courtesy Goulburn-Murray Water).
This is demonstrated in Figure 11.9 with the variation in CPT cone resistance. Note
that S
u
(q
c
vo
)/N
K
(see Section 6.1.7.1).
(b) The core has significant undrained strength at the surface, because the soil is compacted in
a partially saturated condition. In Figure 11.9 the strength is somewhat less above Full
Supply Level (the top 5 m approx.) due to the effects of cracking and softening as water
has entered the cracks. This is not an uncommon feature particularly for central core earth
and rockfill dams with poorly compacted rockfill and is due to spreading of the dam as it
settles as shown in
Figures 11.10
and
11.11
.
The selection of undrained strength and stability analysis should allow for these features
and may include:
-
Allowance for cracks, or softened zones around old cracks with little or no shear
strength. These are unlikely to persist below FSL;
