THE EARTHQUAKE-RESISTANT REINFORCEMENT OF PILE FOUNDATIONS WITH DIAPHRAGM WALL TO LATERAL FLOW OF LIQUEFIED GROUND

连续墙桩基对液化地层侧流的抗震加固

基本信息

批准号：
11650493
负责人：
KATADA Toshiyuki
金额：
$ 2.3万
依托单位：
Musashi Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

According to the centrifugal model experiment carried out in this study, the bending moment of the pile decreased to about the half by the reinforcement of the diaphragm wall. This reinforcing mechanism was clarified by the experiment on this year as follows. The pressure area of the diaphragm wall was bigger than that of the piles. Therefore, the flow pressure of the liquefied sand that affected the diaphragm wall was bigger than that of the piles. Next, the bending moment of the piles decreased by reinforcement of diaphragm wall because the bending rigidity of diaphragm wall is considerably bigger than that of the piles. The diaphragm wall moves as rigid body and the piles move as a cantilever beam of which the tip was fixed, when the liquefied sandy ground flows. This shows that the diaphragm wall must be installed to the sufficient depth of the non-liquefaction layer. The sufficient installation generated the horizontal resistance force of the diaphragm wall by the bearing capacity of the ground. And then, the flow pressure and the bending moment in the piles decreased. But if the range of the liquefaction spreads to the bottom of the diaphragm wall and the bearing capacity of the ground disappears, the diaphragm wall loses the resistance force for lateral flow. As the result, the diaphragm wall flows and large force affects the piles. This generated the large bending moment at the pilesThe conclusions of this research are as follows ; it is important to install the diaphragm wall to the sufficient depth to the non-liquefaction layer, though the reinforcement of pile foundation by the diaphragm wall is the sufficient effect for lateral flow.

根据本研究进行的离心模型试验，通过连续墙的加固，桩的弯矩减少到一半左右。通过今年的实验，明确了这一强化机制如下。连续墙的受压面积大于桩的受压面积。因此，液化砂对连续墙的流动压力大于桩的流动压力。其次，由于连续墙的抗弯刚度远大于桩的抗弯刚度，通过加固连续墙来降低桩的弯矩。当液化砂质地面流动时，连续墙作为刚体移动，桩作为悬臂梁移动，悬臂梁的顶端固定。这说明连续墙必须安装到非液化层足够的深度。充分的安装通过地面的承载力产生地下连续墙的水平阻力。然后，桩内的流压力和弯矩减小。但如果液化范围蔓延至地下连续墙底部，地面承载力消失，则地下连续墙就失去了侧向流的阻力。结果，地下连续墙发生流动，对桩产生很大的作用力。这在桩上产生了很大的弯矩。本研究的结论如下；虽然地下连续墙对桩基的加固足以产生横向流的效果，但重要的是要将地下连续墙安装到非液化层足够的深度。