Geoscience Reference
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Fig. 11.5. Effect of footing widthon liquefaction induced subsidence of shallow
foundations (based on Liuand Dobry, 1997, and Yasuda and Berrill, 2000)
Jitno, 1995). In all cases, a specific velocity time history, for a magnitude 7.0 seismic
event, scaled tovarious peak values, was applied at the base of the liquefiable soil, while
the foundation consisted of a number of equally sized strip footings interconnected by
anirregulartwo-storeystructuralskeleton.Furthermore,liquefactionwastriggeredartifi-
cially at an intermediate stage of the analysis, by setting the stress statein the liquefiable
soil to that of a heavy fluid (equal horizontal normal stresses combined to zero shear
stresses).
In that way, it was finally concluded that liquefaction-induced settlements could be
directlyrelatedtothedegradedfactorofsafety
F
S
(
=
FS
deg
fromEq.11.3)or,forlarger
accuracy, tothe following factor:
F
S
X
S
=
(11.8)
Z
1
/
3
1
/
2
lim
Q
1
/
4
liq
γ
whichtakesalsointoaccountthethicknessoftheliquefiedsand(
Z
liq
inm)andthecorre-
spondingmaximumshearstrainamplitude(
γ
lim
in%).Boththesecorrelationsarerepro-
duced in Figure 11.6. Comparison with field evidence, recalled by the authors, suggests
thatminorornobuildingdamageduetofoundationsettlementscorrespondto
F
S
>
3
.
00
or
X
S
>
1
.
00.
