MODEL TESTS ON THE EFFECT OF CONSTRUCTION ACCURACY ON THE PULL-OUT RESISTANCE OF SPIRAL PILES

Abstract

Spiral piles are made by twisting flat steel plates and can be driven by rotary penetration only by human power, so they are expected to be used in construction sites that are so narrow that heavy machinery cannot enter. However, many points are unclear regarding the bearing capacity characteristics of spiral piles, especially regarding vertical pull-out resistance. In addition, the principle of pull-out behavior assumed at actual construction sites has not been fully clarified. Therefore, in this study, a pull-out test of a model pile was conducted using Toyoura dry sand, and the effects of the degree of construction accuracy, such as over-rotation, pushing, and pile shaking during driving, were examined. The effects of the decrease in construction accuracy for pull-out resistance tended to differ depending on the distance between two piles. These are thought to be caused by changes in the ground density around the piles owing to the placement of the piles.