Laboratory Experiments on Seepage in Liquefied Sand

Abstract

For understanding and modelling the behavior of saturated sand before, during, and after liquefaction, such as drainage, pore pressure build-up and dissipation, and settlement, the permeability of liquefied sand is one of the important soil properties. Previous researches on evaluating the changes of permeability of liquefied sand during and after liquefaction were proposed based on the assumption of drainage flow through the liquefied sand or the application of solidification and consolidation theory. However, these considerations of the water flow and the movements of soil particles did not truly represent the conditions within the soil during and after liquefaction, and the results were not well verified. In this study, a new experimental approach was proposed by combining the simple seepage test and the liquefaction test to evaluate the water flow within the saturated Vietnam silica sand before, during, and after liquefaction. The permeability of the sand was calculated directly from the hydraulic gradient which drove the water flow through the specimen. Results showed that the critical state of the specimen for sand boiling can be predicted well by using the Terzaghi’s theoretical equation. The permeability of liquefied sand during liquefaction was about four times the initial value, while it reduced to 0.9 times the initial value after full dissipation of the excess pore pressures.