2532
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
figure 5. measured and predicted settlement rate for the layer above el
-30m: (a) hansbo
’
s method, (b) proposed method with case a, (c)
proposed method with case b
the surcharge load is assumed to be applied all at once, while, in
the field, the surcharge load is applied incrementally.
4 conclUsion
in this study, the radial consolidation enhanced by the vertical
drain is discussed with the analytical method existed, and the
modified solution is suggested. through parametric study and
comparison between the calculated and measured settlement
rates, the results are summarized as follows.
as the degree of disturbance increases, hansbo
’
s analysis
shows that the time factor t
h
increases for a certain degree of
radial consolidation. however, the time factor for proposed
analysis (t
hs
), which corresponds to a certain degree of radial
consolidation, slightly decreases as the degree of disturbance
increases. furthermore, proposed analysis gives the almost
identical
hs
r
T U
'
curves when the k
h
/k
s
value becomes larger
than 20.
for Busan new-port site, the extent of the disturbed zone is
evaluated using two possible void ratio variations within the
disturbed zone. When a constant permeability or void ratio
within the disturbed zone is assumed, the extent of the disturbed
zone r
s
is estimated to be 2.7r
m
. for the linear spatial variation
within the disturbed zone, the extent of the transition zone r
t
is
estimated to be 4.1r
m
with the same equivalent radius between
fully disturbed zone and mandrel (r
f
= 1.0r
m
).
the settlement rate predicted by the proposed analysis is
well matched with the measured field settlement when the k
h
/k
f
ratio is 2.5 with a linear spatial distribution of the permeability
within the disturbed zone. the proposed method has advantages
to evaluate the extent of disturbed zone and it is less influenced
by the disturbance effect than hansbo
’
s method.
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