Study on the rational design method for treating area against liquefaction based on performance-based design

1995年兵库县南部地震后，建议将抗震设计建立在两种类型的地震动基础上：1级地震和2级地震。在2级地震作用下，目前的对策无法防止液化。因此，有必要引入一种新的设计概念，不是基于液化的发生，而是基于对结构的可能损害程度。基于性能的抗震设计是一种合理的抗震设计方法，本文通过大量的振动台试验和反复扭剪试验，对基于性能的抗震设计方法进行了研究。在振动台试验中，使用了一个模型房屋和松散的桑迪地面。模型房屋下面的一些区域通过致密化得到了改善。在不同的加固深度和宽度下进行了振动台试验。模型房屋的液化沉降随加固深度和宽度的增加而减小。在分析中，一个名为ALID，这已经由作者开发的代码，被使用。还对几个改进领域进行了分析。对改善面积的效果也得到了类似的结果。结果表明，现行的液化处理区设计方法对液化处理区的设计精度估计过高，基于性能的液化处理区设计方法对液化处理区的合理设计具有一定的指导意义。

After the 1995 Hyogoken-nambu earthquake, it suggested basing earthquake-resistant design on two types of ground motion : Level 1 earthquake motion and Level 2 earthquake motion. Liquefaction cannot be prevented by current countermeasures under the Level 2 earthquake motion. Therefore, it is necessary to introduce a new design concept based not on the occurrence of liquefaction but on the likely degree of damage to structures. This new design concept, so called performance-based design, must be rational and will be used for the design for improving area against liquefaction.Then, a study on the rational design method for treating area against liquefaction based on performance-based design, was conducted by many shaking table tests, cyclic torsional shear tests and analyses. In the shaking table tests, a model house and loose sandy ground was used. Some area under the model house was improved by densification. The shaking table tests were carried out under several depth and width of the improved area. Liquefaction-induced settlement of the model house decreased with the increase of the depth and/or width of the improved area. In the analyses, a code named ALID, which has been developed by the author, was used. Analyses were carried out under several improving areas also. Similar results on the effect of improving area were obtained. Then it was concluded that the current design method for the improving area is overestimated, and the performance-based design method is useful for rational design of treating area against liquefaction.