The effect of overburden pressure on liquefaction resistance of sand i
s studied and results ot a site-specific investigation are presented.
When estimating liquefaction resistance of sand from the indirect appr
oach using the chart suggested by Seed et al. (1984) a correction fact
or K(sigma) is applied to account for vertical effective overburden st
resses larger than 1 tsf. Published data indicate a decrease in K(sigm
a) with increased confining stress but with a wide range of K(sigma) v
alues for the same confining stresses, predicting significantly differ
ing liquefaction resistance. The effect of confining stresses on lique
faction resistance was investigated as part of a comprehensive seismic
assessment of Duncan Dam in British Columbia. The results indicate th
at K(sigma) is dependent on confining stresses and the relative densit
y of the soil, and values are generally significantly higher than much
of the previously published data.