Geoscience Reference
In-Depth Information
Figure 5.29
Hyperbolic method to predict future settlement.
For clay soils this method seems to work rather well (Huat, 1996, 2002; Rahim
and George, 2004). For peat soils, Cartier
et al
. (1989) used Asaoka's method for
the analysis of a test embankment on peat and reported a reasonable prediction of
settlement and time of 98% primary consolidation. Edil
et al
. (1991), on the other
hand, applied the procedure to a variety of clay and peat cases and questioned its
applicability to peat settlement.
Another useful method is the hyperbolic method (Tan, 1971; Chin, 1975). This
method is based on the assumption that the settlement-time curve is similar to a
hyperbolic curve and can be represented by the equation:
t
S
=
(5.14)
(
c
+
mt
)
Where
S
is the total settlement at any time after the excess pore water pressure has
dissipated and
m
and
c
are empirical constants. Figure 5.29 shows a plot with the ratio
t
/
S
on the ordinate and time
t
on the abscissa. A straight line gives the intercept
c
with
slope
m
, and the significance of
m
is seen by writing the equation as follows:
1
S
=
c
t
m
+
(5.15)
When
t
becomes very large, i.e.
→∝
, then 1/
t
→
0 and 1/
S
=
m
, which means the
ultimate settlement,
S
ult
=
1/
m
.
Studies carried out by Al-Raziqi
et al
. (2003) showed that this method may be
used for predicting the primary phase of peat settlement. However, for the secondary
(creep) phase, the settlement prediction could be misleading.
