KUWANO Jiro TOKYO INSTITUTE OF TECHNOLOGY, DEPARTMENT OF CIVIL ENGINEERING, ASSOCIATE PROFESSOR, 工学部, 助教授 (30178149)
TSUKAMOTO Yoshimichi SCIENCE UNIVERSITY OF TOKYO, DEPARTMENT OF CIVIL ENGINEERING, RESEARCH ASSOCIATE, 理工学部, 助手 (50253505)
TOUHEI Terumi SCIENCE UNIVERSITY OF TOKYO, DEPARTMENT OF CIVIL ENGINEERING, ASSOCIATE PROFESSOR, 理工学部, 助教授 (50246691)
MORICHI Shigaaki SCIENCE UNIVERSITY OF TOKYO, DEPARTMENT OF CIVIL ENGINEERING, PROFESSOR, 理工学部, 教授 (50013173)
|Budget Amount *help
¥29,700,000 (Direct Cost : ¥29,700,000)
Fiscal Year 1997 : ¥3,200,000 (Direct Cost : ¥3,200,000)
Fiscal Year 1996 : ¥26,500,000 (Direct Cost : ¥26,500,000)
Due to 1995 Hyogo-ken Nambu Earthquake (Hanshin-Awaji Earthquake Disaster), gravel-containing Masado soils at Kobe Port Island were extremely liquefied, which were considered to be less liquefiable than clean sand. This study shows the outcome of experimental investigations on liquefaction characteristics of Masado soils.
First, undrained monotonic compression as well as extension tests were carried out on reconstituted soil samples and intact soil samples recovered from Kobe Port Island. For reconstituted soil samples two different Masado soils having different gradations were used, and two different preparation methods of soil samples ***e adopted in this study. In the test series on reconstituted soil samples, the following experimental findings were found. Stress states at steady states of information are the same independent of sample preparation methods and confining pressures, in the void ratios of the soil samples are the same. The inclinations of the steady state envelopes for
compressive and extensional loadings differ, accordingly, the deviator stresses at steady states for compressive and extensional loading are different. At states of phase transformation, mean effective stress achieved by the soil samples prepared by water sedimentation are lower those prepared by wet tamping. In the test series on intact soil samples, it was found that the intact soil samples shows mainly dilative behavior. The relationship between void ratios and mean effective stresses for the intact soil samples shows much scatter, probably due to a variation in gradations of the soil samples.
Then, large-scale triaxial test apparatus with a hydraulic actuator, which enables constant amplitude motions as well as random earthquake motions to be applied to soil samples, were installed, and a series of experiments were carried out. First, undrained cyclic tests were performed on dense Toyoura sand, and the test results were verified against the existing published test results. Then, undrained tests subject to the earthquake motions, which were recorded at the time of 1995 Hyogo-ken Nambu Earthquake, were performed on dense Toyoura sand, and the influence of the characteristics of strong motions, I e. impulse-type or vibration-type, was examined. Finally, undrained tests under constant-amplitude and earthquake motions were performed on Masado soils, and it was found that liquefaction strengths of Masado soils are lower than those of dense Toyoura sand at lower number of cycles, and the characteristics of earthquake motions have less influence on the liquefaction of Masado soils.