Tadashi Kawai

Density Index for Estimating the Postliquefaction Volumetric Strain of Silty Soils

AbstractThis study examined the liquefaction-induced ground settlement of silty sand ground, in which many nonplastic fines are contained. Investigation determined that if fines were included in the specimen, the minimum void ratio shrank more under water-immersion than dry conditions. In addition, the cyclic minimum void ratio was examined, which was obtained by cyclic liquefaction and drainage testing conducted by assuming earthquake excitation. The results illustrated that the difference between the estimated dry and cyclic minimum void ratios uniquely correlated with fines content. A new density index, the normalized margin of void ratio, was proposed for postliquefaction volumetric strain based on examination of the minimum void ratio of soils containing nonplastic fines. The test results confirmed that maximum and accumulated shear strains are satisfactory indices of loading history. Furthermore, the normalized margin of void ratio performed well as a density index for estimating postliquefaction se...

Subjects of the liquefaction research seen to the liquefaction damage of the Great East Japan Earthquake Disaster

This paper discusses the new subjects of the liquefaction research regarding the liquefaction damage of the Great East Japan Disaster. Specifically, the subject about the liquefaction potential assessment, the subject about the evaluation of ground subsidence caused by liquefaction and the subject seen to generate the liquefaction damage of a river levee, etc. are discussed based on the damage observed or the experimental results. It has been shown that understanding current damage on the extension of the present technology has a limit, and that the prediction and countermeasure technology of the liquefaction damage based on a new concept is necessary.