Cyclic Stress Conditions Causing Liquefaction of Sand

Liquefaction of saturated sand was studied using a cyclic loading triaxial test. Quantitative data were obtained providing numerical values for the several important factors necessary to produce liquefaction. Under cyclic loading, four different conditions must be considered; initial liquefaction, partial liquefaction, complete liquefaction, and failure. At relative densities below about 50%, these three conditions occurred almost simultaneously, whereas for relative densities above about 80%, a considerable number of stress cycles were required after initial liquefaction to develop large strains defining a failure condition. There was an approximately linear relationship between the relative density and the stress required to cause initial liquefaction in a given number of cycles. It was also found that the magnitude of cyclic stress required to cause initial Iiquefaction increases almost linearly with confining pressure. Suggestions are presented as to applications of this type of data in predicting the susceptibility of a field deposit to liquefaction during an earthquake.