Liquefied ground loses its stiffness and strength, and it flows laterally in sloping areas and backfill areas behind collapsed quay walls. The characteristics of soil have to be changed in order to prevent the lateral flow of liquefied soil. However, their construction cost is high and impracticable when the target area spreads widely. The improvement method should be more feasible. The authors are investigating the most effective arrangement of DM piles to optimize cost-effectiveness. It is proposed to irregularly displace the DM piles to prevent lateral flow in various directions.
In the present study, centrifuge model tests and analyses were conducted to clarify the improved effect of the DM piles against the lateral flow and its arrangement in detail. In addition, the field tests were conducted to investigate integrity between DM piles and shallow mixing layer. The results of the model tests and numerical analyses showed that the improvement by the DM piles dramatically reduced the lateral displacement and that the average total flow velocity was small in the irregular arrangement case. The lateral load acting on the DM pile from liquefied ground, which is required for design strength of the DM pile, was investigated in the field tests. It verified the structural integrity of DM piles and shallow mixing layer.
Key Words: liquefaction, lateral flow, deep mixing method, centrifuge, fluid analysis