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

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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.