Abstract
The aim of this paper is to examine the mechanism attributing to re-liquefaction. We observed the distribution of sand boiling from the model ground with a series of shaking table tests. The test results show that sand boiling tends to occur at the same place repeatedly as before. We then conducted shaking table tests to measure the shear resistance distribution along the depth in the model ground with a hand vane apparatus. The shear resistance of sand deposit after liquefaction was found to increase only at the bottom part of the model ground. The reason of the non-increase or decrease of shear resistance from the surface to a critical depth was considered to be caused by the upward seepage flow. The shear resistance of sand deposits subjected to a quick sand condition in the seepage tests was found to be similar to those in shaking table tests. Based on the experimental results, the repeated occurrence of liquefaction can be believed to occur due to the disturbance provided by upward flow, which prevents the increase of density of liquefied sand from occurring during the process of dissipation of pore water pressure after liquefaction.
