Yuhei Nishimura

Effects of fine-grain fraction and sand density on mechanical properties of sand consolidated long-term

Hirofumi Toyota

�@The liquefaction that occurred during the 2011 Tohoku earthquake was mainly observed in reclaimed lands. A difference in liquefaction damage was seen on the construction age even in the same reclaimed land. This indicates that liquefaction resistance is increased by aging. Aging is the phenomenon that liquefaction resistance is increased with time passing after the sedimentation. However, it is difficult to think that sand has cementation even for several hundred years. Although factors that affect liquefaction resistance are considered as fine content, density, degree of saturation, confining pressure, etc., the mechanism of aging is uncertain in the present conditions.
�@Therefore various mechanical experiments were conducted using specimens created from Toyoura sand having different relative density (40 and 60%) and Toyoura sand with 5% kaolin, which were consolidated for long term. The objectives of the study is to elucidate the influence of fine content and density on mechanical properties.
The following conclusions were obtained.

Effects of fine content:
1. An increase of liquefaction resistance and expansion of elastic region were observed in earlier time on Toyoura sand with 5% kaolin than those on Toyoura sand. Therefore, there is a possibility that the expansion of elastic region affects liquefaction resistance.
2. The initial elastic shear modulus did not show the remarkable change during the consolidation period.

Effects of density:
1. An increase of liquefaction resistance was observed in earlier time on dense Toyoura sand than that on loose Toyoura sand.
2. The initial elastic shear modulus did not show the remarkable change in both loose and dense Toyoura sand during the consolidation period.
3. The penetration resistance did not show the remarkable change in dense Toyoura sand during the consolidation period.