CHAVEZ GARCIA CARLOS ALAIN

Relations between sand particle orientation varied by triaxial liquefaction tests and liquefaction resistance

Hirofumi TOYOTA

Various studies of liquefaction have been conducted on effects of density and aging. However, effects of anisotropy on liquefaction is still uncertain because the studies of anisotropy have been only conducted on strength. This research aims to elucidate the relationship between sand particle orientation and liquefaction resistance. Test specimens were prepared in an inclined mold at orientations of 0-degree (horizontal particles), 45-degree, and 90-degree (vertical particles). To assess the actual particle orientation, the particle orientations of the prepared specimens were measured through a microscopy. It is necessary to prepare the individual 6 specimens before and after liquefaction because of comparison in particle orientation between before and after liquefaction. Approximately 500 particles were measured for its orientations in each case within a range of 0-degree to 180-degree.

The specimens created using Toyoura sand were used for understanding of their mechanical properties, in which liquefaction tests, local strain tests, and bender element tests were conducted using triaxial apparatus. Microscopic readings of particle orientation revealed that particles in the cases of 0-degree and 45-degree deposition angles shifted towards an orientation of 90-degree after liquefaction, while 90-degree particles decreased in the 90-degree deposition angle. The liquefaction strength test results indicated that 90-degree deposition angle had greater liquefaction strength than 0-degree deposition angle. Regarding reliquefaction strength, it increased in the 0-degree and 45-degree deposition angles but decreased in the 90-degree deposition angle. Those results can be partly explained from the change of particle orientations during liquefaction. Bender element test results indicated that shear modulus increased in the order of 0-degree, 45-degree, and 90-degree deposition angles. After liquefaction, the shear modulus has the same trend with the liquefaction tests: an increase in the 0-degree and 45-degree deposition angles, and a slight decrease in the 90-degree deposition angle. Therefore, it was confirmed that there is a strong correlation between liquefaction strength and shear modulus.