Kenyu TAZAKI

Relationships Between Shear Wave Velocity And Liquefaction Strength in Sandy Soils

Hirofumi TOYOTA

Surface wave explorations from which the shear wave velocity distribution in the ground can be easily estimated with low-cost and non-destructive have recently drawn considerable attention. Because the shear wave velocity obtained from the exploration has a close relation with N-value and the physical properties of soils, the soundness evaluation system for ground using this relationships has been developing. On the other hand, it is a serious problem that frozen sampling, which is very expensive, is commonly necessary to estimate the liquefaction strength of the ground. In the present study, disturbed samples were obtained subjecting liquefiable grounds without aging effect to estimate the relationships between shear wave velocity and liquefaction strength. Then, the experimental validation was conducted to examine the possibility of the liquefaction strength of the ground. Especially, the examination paid attention to the over-consolidated history was carried out among various kinds of stress and strain histories that the ground received.
 The results obtained in the study are follows:
1. It has been clarified that when the over-consolidation ratio, OCR, increases, the shear wave velocity also increases even in the almost same void ratios.
2. It has been clarified that when OCR increases, the liquefaction strength also increases even in the almost same void ratios.
3. The liquefaction strength can be estimated from the shear wave velocity using a pseudo-void ratio in the case of loose and over-consolidated Toyoura sand.
4. The estimation method was only verified in loose and over-consolidated Toyoura sand. Therefore, it is necessary that the same type of the experiment should be conducted in various kinds of soils and stress histories such as earthquakes.