Determination of Threshold Ground Acceleration for Soil Liquefaction Using the Strain and Stress Approaches

Abstract

The evaluation of soil liquefaction using the stress approach utilizes the relative density and initial confining stress available at the layer subjected to liquefaction. The shear strain approach makes use of the shear modulus which is a more fundamental property of materials. The threshold ground acceleration values for forty layers at ten selected sites were evaluated using the stress and strain approaches. For the stress approach, the method proposed by Shibata and Teparaksa (1988) based on the concept of critical cone tip resistance was selected. For the strain approach, the method proposed by Dobry and others (1981) was employed. The threshold ground acceleration values computed using the stress approach were found to be two to four times higher than those computed using the strain approach. Several scenarios were tested in order to incorporate the effect of variations in the threshold shear strain and the ratio of (G/Gmax)t. The results of the stress and the strain methods are based on site response analyses performed using the program SHAKE91 and the input ground motions of the 1988 Saguenay earthquake.