The Mechanism and a Simplified Procedure for the Analysis of Permanent Ground Displacement Due to Liquefaction

ABSTRACT To study the mechanism of permanent ground displacement due to liquefaction, shaking table tests on 24 soil models were conducted. In these models, the slope of the ground surface, the thickness of a liquefied layer, the density of the liquefied layer and some other factors were changed. Permanent ground displacements did not occur at the boundary between the liquefied layer and the lower non-liquefied layer, but occurred in the liquefied layer with a constant shear strain. Relationships between the displacement and the thickness of the liquefied layer or the slope of the ground surface were also obtained. Then, vane shear tests and cyclic torsional shear tests were carried out to measure the rate of reduction of shear strength or shear modulus. By the cyclic torsional shear tests, it was clarified that the shear modulus decreases to a very small value due to liquefaction. Based on these test results, a simplified procedure for the analysis of permanent ground displacement was proposed. To confirm the accuracy of this procedure, it was applied to the models used for the shaking table tests and to typical soil cross sections of soil at Niigata City. Finally, some measures to prevent permanent ground displacement were discussed based on the shaking table tests and analyses.