PILE SHAFT RESISTANCE PARTIALLY OVERLAPPING WITH BACKFILLED SOILS OF VARIOUS PROPERTIES

Abstract

When a building is reconstructed, many existing piles that support the building are removed. After removing large-diameter piles, the holes are backfilled with various materials. In this study, vertical loading model tests were conducted for the case where a newly constructed pile overlaps clayey backfill columns whose properties differ from those of the surrounding sandy soil. The influence of the variation of the unconfined compressive strength of clayey soil backfill on the shaft resistance of a pile was investigated. The results indicated that the process of soil failure up to the maximum pile shaft resistance varies with the strength of the clayey soil backfill. The maximum shaft resistance of the pile was calculated based on the failure criteria of the soil and the cavity expansion theory, and the strength effect of the clayey soil backfill was estimated. For the pile shaft resistance overlapping partially clayey backfill columns in sandy soil to be equal to the pile shaft resistance in a homogeneous sandy soil, the shear strength of the clayey soil backfill must be higher than the pile shaft resistance in a homogeneous sandy soil.