Analysis of multiple liquefaction characteristics of Toyoura sand under initial static shear based on dissipated energy

抄録

It has been reported that the liquefaction resistance of sand is largely influenced by cyclic shear history as well as the density. There are several studies proposing that dissipated energy during cyclic shear can be associated with the liquefaction resistance at next undrained cyclic shear. These previous studies only considered experimental conditions equivalent to horizontal ground where cyclic shear is symmetric. However, sloped soil or soil near structure is subjected to static shear stress and cyclic shear the soil experience during an earthquake is biased to one direction. In this study, analysis of the multiple liquefaction resistance under initial static shear was newly conducted based on dissipated energy. Experimental data by Morimoto et al. (2019a), who conducted multiple liquefaction tests on Toyoura sand using stacked-ring shear apparatus, were used. Dissipated energy is calculated by integrating the shear stress - shear strain curve during the cyclic shear. In addition to the traditional dissipated energy, the normalized dissipated energy, which uses the shear stress normalized by the mean effective stress instead of the shear stress, is also analysed as Wahyudi and Koseki (2015) and Aoyagi and Koseki (2017) did. The relationship between the liquefaction resistance of Toyoura sand and the dissipated energy (or the normalized dissipated energy) applied during previous cyclic shear is analyzed.