饱和及非饱和粉土中扩底桩极限上拔承载力大尺寸模型试验研究

 通过采用大比例尺模型对饱和度为49%的非饱和粉土及饱和粉土中埋深比(桩埋深与扩底直径之比)为1，2，3和5的扩底桩进行试验研究，揭示饱和度、埋深比对扩底桩极限上拔承载力及其破坏模式的影响。试验结果表明：土体饱和度从49%增加至100%，扩底桩的极限上拔承载力降低至原来的30%～50%；扩底桩埋深比从1增加至5，非饱和及饱和土中桩的极限上拔承载力分别增加8和12倍；扩底桩的上拔破坏模式随埋深增大由桩周土体倒圆锥台形破坏变为扩底圆周土体局部破坏。

LARGE-SCALE TESTS ON UPLIFT ULTIMATE BEARING CAPACITIES OF ENLARGED BASE PILES IN SATURATED AND UNSATURATED SILTY SOILS

Two groups of tests have been conducted in a large-scale model chamber，and each group contains four uplifting tests with embedment ratios(embedment depth to enlarged base diameter) of 1，2，3 and 5，respectively. One group of tests was conducted in unsaturated slit with degree of saturation of 49% and the others in saturated silt soil. The effects of soil saturation and embedment ratios on the ultimate bearing capacity and the failure patterns of the enlarged base piles are discussed. It is found that the uplift ultimate bearing capacities of the enlarged base piles decrease 30%–50% while the degree of saturation of silty soils increases from 49% to 100%，but 8 and 12 times larger while embedment ratios increase from 1 to 5 in unsaturated slity soil and saturated slity soil，respectively. The failure pattern of the soil around the pile changed from inverted truncated cone slip-surface to local failure around the enlarged base with the increase of embedment ratio.