Shusei OGAWA
Relationships between secant shear modulus and liquefaction strength in gravel-mixed sand of different densities
Hirofumi TOYOTA
Liquefaction generally occurs in the loose sandy ground with high groundwater level. However, it has been reported that liquefaction occurred in gravelly ground during the 1995 Kobe Earthquake. Nevertheless, few studies have been conducted on
liquefaction of gravelly soil. Therefore, the purpose of this study is develop liquefaction evaluation technique in the ground having wide range of particle size. Various effects of gravel content on liquefaction were examined with taking attention
to the relevance of wave propagation properties and small deformation characteristics. Moreover, Experiments were conducted using the loose specimen with initial relative density of 35%. Then effects of density on liquefaction estimation were
examined comparing the results with the specimen with initial relative density of 75%, which was conducted last year. The results obtained in the study are follows:
(a) Liquefaction characteristic of gravel-mixed sand:
When gravel content exceeds 20% in mass, liquefaction strength increases.
(b) Small deformation properties of gravel-mixed sand:
If gravel content is less than 20%, a secant shear modulus slightly increases. When gravel content reaches 30%, a secant shear modulus greatly increases.
(c) Initial shear modulus obtained from wave propagation and small deformation tests:
Initial shear modulus obtained from the small deformation test is larger than that from the wave propagation test. The difference between those initial shear modulus becomes larger with increase of gravel content.
(b) Wave propagation and small deformation properties related to liquefaction strength:
First, the liquefaction strength has close relation with a secant shear modulus of about 0.04% shear strain. Therefore, there is a possibility that liquefaction strength can be precisely estimated using this kind of secant shear modulus in the
grounds with various densities.
Second, the normalized relationship between shear modulus and shear strain, where a secant shear modulus is normalized by the initial shear modulus, were demonstrated. A technique to estimate liquefaction strength was proposed in the grounds with
various density using this relation and shear wave velocity obtained from in-situ investigation
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