Earthquake Engineering Support, Phase 2

This project is a continuation of earlier research work by the Principal Investigator in support of the Earthquake Engineering Research Program, under the direction of the USAE Waterways Experiment Station at Vicksburg, Mississippi. The program of experiments investigating the earthquake behavior and liquefaction of deep sand deposits has generated a large body of data for analysis. This Final Technical Report describes the database that has been developed to date and presents the analysis and the initial conclusions of the study. Data of excess pore pressures at different depths is used to deduce the onset of liquefaction under different initial effective overburden stresses. The object of the research is to compute the factor K(sigma), widely used in design calculations to relate the liquefaction resistance at high effective confining stresses to the strength deduced from laboratory experiments at 1 tsf. By comparing the data obtained from the centrifuge experiments with standard design approaches for the prediction of liquefaction, an assessment of the relationship between K(sigma) and depth can be made. This is discussed and areas where further experimental work is required are highlighted. The results are also presented in the form of log-log (stress focus) plots and compared with laboratory element test data. Preliminary conclusions indicate that the centrifuge data more closely match relationships based on field experience than laboratory data.