Evaluation of Liquefaction Potential with Simplified Method and Effective-Stress Site Response Analysis

Evaluation of liquefaction susceptibility is an important part of the seismic design of structures, which is. The simplified method, which relates the equivalent shear stress due to the earthquake and resisting shear stress, is widely used in practice. However, the accuracy and applicability of the simplified method to domestic sites are not well known or documented. This paper evaluated the applicability of the simplified procedure by comparing the results of the simplified method and the effective-stress nonlinear site response analysis at Pohang and Kwangyang using ground motions representative of earthquake with return periods of 1000 and 2400 years. Comparison showed that the predictions of the liquefaction susceptibility are significantly different. The simplified method constantly predicted higher susceptibility to liquefaction compared to effective-stress site response analysis results. The discrepancy between the estimated susceptibility was especially large for motions representative of seismic hazard with return period of 1000 years. In addition, the estimated variations of the pore pressures within the soil column were distinctively different. The comparisons demonstrated that the simplified method can be used as a preliminary evaluation procedure, but a more advanced model should be used for an accurate evaluation of the liquefaction susceptibility.