Environmental Engineering Reference
In-Depth Information
Figure 6.43.
Drained Youngs Modulus E
for sands versus SPT “N” value (Ohya et al., 1982; from
Kulhawy and Mayne, 1988).
6.2.2.2 Using data from the performance of other dams - rockfill
See Section 15.2.4.
6.2.2.3 In-situ testing
The drained modulus E
for free draining soils, such as sands, silty sands and fine gravelly
sands, and the undrained modulus Eu for clayey soils can be estimated using Standard
Penetration and Cone Penetration Tests.
Figures 6.43 and 6.44 show plots of E
and Eu respectively versus SPT “N” value. The
moduli were obtained by pressuremeter testing. It will be seen that there is a considerable
uncertainty in the relationship between the moduli and SPT “N” value. Note that the
moduli are in bars, where 10 bars
1 MPa.
Figure 6.45 presents a chart to estimate the secant Young's modulus (E s
) for an average
axial strain of 0.1% for a range of stress histories and aging. This level of strain is reasonably
representative for many well-designed foundations. In Figure 6.45 a
100 kN/m 2 and
mo
is the mean stress level
(
vo
2
Ho )/3. The stiffness of normally consolidated aged sands
(
1,000 years) appears to fall between that of very recent normally consolidated sands and
over-consolidated sands.
Recent sands would include those deposited by dredging, or in historic time by for
example scour and deposition in river channels.
Kulhawy and Mayne (1988) produced Figures 6.46 and 6.47 showing the relationship
between M/q c (
n ) and relative density for normally consolidated (NC) and over-
consolidated (OC) sands. As can be seen there is a trend for decreasing
n with increase in
relative density, but a large scatter of test data. Note that:
E
(
1
)
M
(6.42)
(
1
) (
1
2
)
Search WWH ::




Custom Search