Evaluation of cyclic resistance of high quality undisturbed Chiba silty sand samples retrieved by "Gel-Push" sampling technique

抄録

This paper focuses on the cyclic resistance assessment of two non-plastic silty sands that likely experienced severe liquefaction during the 2011 Off the Pacific Cost of Tohoku Earthquake (Japan). Several samples were retrieved from fill and alluvial deposits at a site investigation in Chiba. Besides a conventional triple-tube sampler (TB), a cutting-edge sampling technique, namely “Gel-Push sampler” (GP), was adopted to obtain high quality undisturbed samples. In the laboratory, a series of cyclic triaxial tests were conducted on several specimens recovered by both GP and TB samplers. Preliminary results of liquefaction resistance and shear wave velocity compared to field PS logging measurements revealed that that the sampling technique and quality of samples highly affected the evaluation of liquefaction resistance of the investigated sands. Therefore, to address this issue, a classification of sample quality for undisturbed samples was provided, based on change in density and shear velocity/dynamic shear modulus measured in the field and in the laboratory.