Effects on Reliquefaction Resistance Produced by Changes in Anisotropy During Liquefaction

Abstract

A distinctive characteristic of the reliquefaction behavior of soils is that there are instances where the phenomenon of a sharp decrease in liquefaction resistance occurs in spite of increases in soil density caused by drainage of water after liquefaction. On the other hand, there have also been examples of increased liquefaction resistance occurring throughout a soil's liquefaction history that cannot be explained merely by density increases. These facts point to the existence of factors other than density that sway the liquefaction resistance of soils. The current paper demonstrates that, in fact, anisotropy is an important factor influencing liquefaction resistance. This is made clear through the results of systematic triaxial shear tests, which show that the higher the level of developed anisotropy, the lower the liquefaction resistance. In the process of verifying the above, we found that continuous and orderly changes in anisotropy are repeated with dizzying rapidity during liquefaction. Furthermore, we show herein that there is no intrinsic difference between the inherent anisotropy acquired by soil during its sedimentation period and the induced anisotropy produced by plastic deformation developed through its stress history, although anisotropy has often been divided into these two types and has been considered separately in the past. We also show that what has been referred to as inherent anisotropy is nothing more than the initial state of induced anisotropy.