EFFECT OF OVERBURDEN PRESSURE ON LIQUEFACTION RESISTANCE OF SAND

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.