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

根据本文所进行的离心式模型试验，地下连续墙的加固使桩的弯矩减小了一半左右。这一增强机制通过今年的实验阐明如下。地下连续墙的受压面积大于桩的受压面积。因此，影响地下连续墙的液化砂的流动压力大于桩的流动压力。其次，由于地下连续墙的抗弯刚度远大于桩的抗弯刚度，因此地下连续墙加固降低了桩的弯矩。液化砂土地基流动时，地下连续墙按刚体运动，桩按端部固定的悬臂梁运动。这说明地下连续墙必须安装到非液化层的足够深度。充分安装后，地下连续墙的水平阻力由地基的承载能力产生。从而减小了桩内的水流压力和弯矩。但如果液化范围扩展到地下连续墙底部，地基承载力消失，地下连续墙就失去了侧向流动的阻力。因此，地下连续墙产生流动，桩受力较大。本文的研究结论如下：地下连续墙对桩基的加固作用足以产生侧向流，但在非液化层中设置足够的深度是非常重要的。

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.