DEVELOPMENT OF EVALUATION METHOD FOR LIQUEFACTION OF GROUND CONSIDERING DUCTILE NATURE

目前的液化预测方法给出了是否没有液化损害的替代结论。但是，从阪神大地震等液化灾害的实际情况来看，液化灾害的等级是不断变化的。这是因为地震运动的荷载水平作为外力而使地面的韧性不断变化。特别是目前还没有一种技术可以定量地评价土的现状韧性。因此，我们不能区分刚性恢复的致密砂土和无延性的松散砂土的断裂事件。本研究的目的是发展定量评价土壤延性的技术。1998会计年度提出了一种定量评价土壤延性的应变控制试验新方法。在此基础上，对除砾石外各种含砂率和细粒率组成的土壤进行了适用性试验。用塑性应变能对试验结果进行了研究，结果表明，塑性应变能是反映土体延性指标的指标。1999财政年度提出的地震烈度作为外力与强度指标成比例的评价方法。也就是说，提出了当某地震运动输入时，用于地基塑化的能量的预测程序。研究成果已于2000财政年度发表。研究结果在国内外学术期刊及国际会议上发表。此外，该研究报告作为科学研究资助报告印刷，并分发给同一领域的研究人员。

Current prediction method of liquefaction issues the alternative conclusion of whether there is no liquefaction damage. However, according to the actual liquefaction damage such as the Great Hanshin Earthquake, it is clear that the damage level continuously changed. This is because load level of the earthquake motion as an external force and the toughness of the ground continuously change. Especially, there is no technique that quantitatively evaluates it on the toughness of the soil in present state. Therefore, we can not distinguish the fracture event between of dense sandy soil in which the rigidity recovers and of the loose sand without ductile nature. The purpose of this study is to develop the technique that can quantitatively evaluate ductile nature of the soil.New strain controlled-test method that could quantitatively evaluate ductility of the soil was proposed in the 1998 fiscal year. Based on this proposed technique, the applicability was examined for various soil composed of sand content and fine-grain fraction except for gravel. The experimental result was studied in plastic strain energy, and it showed becoming an index which shows ductility index of the soil.The evaluation technique of earthquake intensity as an external force in proportion to the strength index proposed in the 1999 fiscal year. That is to say, the prediction procedure of energy amount used for the plastication of the ground was proposed, when some earthquake motion input it.The research result was presented in the 2000 fiscal year. And the result of this study was published in academic journal and international conference of domestic and overseas. In addition, the research report was printed as a grant-in-aids for Scientific Research report, and it was distributed to the researcher of the same field.