Preparation of fully saturated models for liquefaction study

Abstract

The degree of saturation significantly influences the liquefaction resistance of sandy soils. In preparation of models for dynamic centrifuge tests and 1g shaking table tests, however, the degree of saturation has not been accurately controlled. A technique to prepare fully saturated model ground for liquefaction study is summarised in this paper, focusing on how vacuum pressure and centrifugal acceleration during the saturation process affect the degree of saturation. A method to evaluate degree of saturation of models accurately is developed first. Then, a total of ten experiments were conducted in which water was introduced to dry sand deposits at different atmospheric pressures at different centrifugal accelerations. It is confirmed that increased acceleration contributes to enhance degree of saturation and reduces time for the saturation process. Two dynamic centrifuge tests on models with different degrees of saturation, one almost fully saturated and the other slightly unsaturated, with the difference in degree of saturation between the two models being 1·5%, were conducted. Differences in excess pore pressure responses between the two models became more significant as the depth increased. It is concluded that a precise control of degree of saturation on the order of 0·1% is important in model tests related to liquefaction problems.