Influence of Perforated Soils on Installation of New Piles

In recent years, there has been an increasing demand to replace ancient structures. The removal of such structures also involves the removal of the existing piles that supported the structures, and the backfilling of the pulling-out holes that formed during the removal. However, there are no standard guidelines for the backfilling of pulling-out holes. At present, therefore, each owner or contractor must determine the material and the construction method to use for backfilling. This results in a difference between the mechanical properties of the original soil and those of the soil that has been backfilled, namely, the soil on which a newly built structure will be constructed. In this study, it was assumed that a new pile would be installed on a perforated soil (that is, the soil left after removing the existing piles) where the mechanical properties differ between the original soil and the backfilled soil. The behavior of the new pile, when installed on the boundary of a soil between two types of mechanical properties, was evaluated by a three-dimensional linear elastic analysis. When the new pile was installed at the boundary between the two types of soil with different mechanical properties, most of the new pile was inclined to the soil side where the N value was relatively small. However, the inclination of the new pile was able to be suppressed by increasing the distance from the boundary between the two types of soil.