2015 年 1 巻 6 号 p. 17-22
The bearing capacity of an open-ended pile depends largely on the degree of soil plugging. Many factors including pile diameter, relative density and the end conditions of piles may influence the degree of soil plugging. The degree of soil plugging is mainly described by the incremental filling ratio (0 and 100% of it imply a fully-plugged and unplugged state respectively). In this paper, the effects of pile diameter and height of an inner sleeved attached to the base of an open-ended pile on the incremental filling ratio are discussed. The experiments were conducted on a medium-dense sandy ground using small-scale model piles. The experimental results suggest that the bearing capacity is influenced by the sleeve height for 50 mm diameter piles while it is independent for 30 mm diameter piles, probably due to the influence on the inner frictional resistance. The results also indicate that a longer sleeve produces a shorter soil plug regardless of the pile diameter. The results of the incremental filling ratio show that the penetration of non-sleeved piles is closer to the unplugged state than the sleeved piles. The results of the IFR also reveal that the degree of soil plugging is affected by the sleeve height of a slightly larger diameter piles of 50 mm while it is independent for 30 mm diameter piles. While the degree of soil plugging remains same after a depth of roughly 1D penetration (D is pile outer diameter) for 50 mm diameter piles, it linearly increases (i.e., decreasing IFR) with the penetration for 30 mm diameter piles.
