Particle orientation influences on liquefaction and reliquefaction resistance during shaking table tests: comparison with triaxial test results

This study using a series of shaking table (ST) tests examines effects of particle orientation on the liquefaction and reliquefaction resistance of Toyoura sand. The ST tests were conducted on model grounds with initial particle orientations of 0°, 45°, and 90° prepared using air pluviation (AP) at relative density ( D r ) of 60%. The ST results revealed pronounced orientation-dependent anisotropy, with 0° ground exhibiting the highest liquefaction resistance ( CRR ), 45° ground showing intermediate CRR , and 90° ground showing the lowest CRR . During reliquefaction, CRR decreased remarkably for the 0° and 45° orientations but it was slightly higher for the 90° orientation, suggesting the influence of particle reorientation. The changes in CRR between liquefaction and reliquefaction were well explained by variations in particle orientation, as evaluated using two-dimensional optical microscopic image analysis. Liquefaction caused distinct particle reorientation, with the mean orientation angle ( θ ) increasing for the 0° and 45° specimens and decreasing slightly for the 90° specimen. At the same time, a corresponding reduction in vector magnitude ( VM ) was observed, reflecting the randomization of particle orientation during liquefaction. These microscopic observations confirm that reorientation was generated through upward seepage flow during liquefaction. These ST test-derived trends were compared with supplementary triaxial (TX) test results, showing an opposite CRR trend (highest at 90°) during liquefaction. This finding suggests the importance of the difference between loading direction and particle orientation, not only that of particle orientation alone.