Geoscience Reference
In-Depth Information
Figure 5.27
w/N
log
σ
v
σ
(
after
den Haan and El Amir, 1994).
−
where
ε
=
compression strain
w
o
=
initial water content
N
=
loss of ignition
w
=
water content, given by the following equation:
26
.
7
σ
v
σ
−
0
.
437
w/N
=
(See Figure 5.27)
σ
v
is the final stress in kPa.
5.5 OBSERVATIONAL METHODS
Because of the difficulties associated with correlating laboratory behaviour with the
field, it is desirable to use field observations to determine the mechanical properties
governing the settlement time behaviour. Asaoka's (1978) observational procedures
use early field settlement data to predict the end of primary settlement and the
in situ
coefficient of consolidation. This method has enjoyed increasing popularity, especially
for consolidation of clays. In the Asaoka method, the one-dimensional consolidation
settlement
S
1
,
S
2
,
S
3
,
S
n
−
1
,
S
n
etc. at times 0, d
t
,2d
t
, etc. (i.e. at equal time increments)
can be expressed, as a first-order approximation, by:
S
=
α
+
β S
n
−
1
(5.10)
