Jin Koen

Effect of Sand Particle Orientation on Liquefaction Resistance in Triaxial Tests

Hirofumi Toyota

The mechanical behavior of sandy soils strongly depends on particle shape and interparticle contacting conditions. Among these factors, particle orientation plays a significant role such as the particle stability against shear deformation. Therefore, it is considered a key factor influencing strength anisotropy and liquefaction resistance. Previous studies using particle-oriented specimens have revealed the effects of particle orientation angles on compressional strength and liquefaction resistance through triaxial tests. These studies primarily addressed inherent (depositional) anisotropy. However, the mechanical characteristics of isotropic specimens without particular particle orientation are also of fundamental interest. In natural environments, soils created through a weathering process may result to form random particle orientation, in contrast to water or wind sedimentation process. Such specimens are referred to as randomly oriented specimens.

In this study, a method for which thin rods were repeatedly inserted into deposited sand specimens to disturb particle alignment (hereafter referred to as the sticking method, SM) was employed to produce randomly oriented specimens. Mechanical properties and particle orientations were examined and compered between the SM specimens and the specimens with controlled orientation angles of 0°, 45°, and 90° (referred to as the AP specimens). The main findings are summarized as follows.
(1) The SM method successfully eliminated particular particle orientation because mechanical properties obtained from triaxial tests and microscopic image analysis of the particles present independent results of particle orientation.
(2) Monotonic compressional strength followed the order of 0°>45°>90°for the AP specimens, exhibiting a significant difference between 0° and 90°. The strength of the SM specimens was close to that of the 45°AP specimens, resulting in a reduction in strength anisotropy induced by particle orientation.
(3) Liquefaction resistance in AP specimens exhibited the opposite trend from the monotonic compressional strength, namely 90°> 45°>0°.　The SM specimens had intermediate liquefaction resistance between 0° and 90°AP specimens, showing close to those of the 45°AP specimens.