MD RASHEDUL ISLAM

Shaking table tests on liquefaction strength considering orientation of sand particles

Hirofumi TOYOTA

This study investigates the influence of sand particle orientation on liquefaction resistance using shaking table tests. Toyoura sand was used to prepare model ground with relative densities of 30% and 60%. The model ground was prepared using the air pulviation method. The horizontal shaking was applied to the ground having three different orientation angles: 0°, 45°, and 90°. A range of input accelerations (200, 225, and 250 gal) was used for simulating seismic loading conditions.

The results showed that samples with a 0° orientation (horizontal alignment) exhibited the highest liquefaction resistance, followed by 45° and 90°. This trend was consistent in both relative density conditions, although denser ground showed greater liquefaction strength. Microscopic observations revealed that after the first shaking, particles tended to realign in a more vertical direction. This reorientation weakened the soil structure and reduced reliquefaction strength because of loss of stable particle structure against shaking.

Reliquefaction tests, simulating aftershock behavior of the ground, confirmed that all samples exhibited lower strength during the second shaking phase. The reduction in strength was attributed to vertical particle realignment, which made the soil particles more prone to deformation. Additionally, the differences in liquefaction strength among the orientation angles became less significant after reliquefaction, because particle alignment became more similar in all cases through liquefaction history.

These findings emphasize the critical role of particle orientation in influencing both initial liquefaction and subsequent reliquefaction behavior. Understanding this mechanism can provide a new evaluation method of liquefaction potential and can improve seismic design cords in the practice of geotechnical engineering.