自重湿陷性黄土场地的桩基浸水载荷试验

Submerged static load test of pile foundation in collapsible loess area

在自重湿陷性黄土场地上进行了钻孔灌注桩(桩径为0.8 m,桩长为18 m,浸水坑边长为20 m)大型原位浸水载荷试验,设置了天然状态下和浸水状态下的2种工况,对试验结果进行了对比分析。研究结果表明:在模拟历史上月最大降水量3倍的试验浸水量条件下,浸水主要影响区域在地表下8.5 m以内;浸水试桩侧摩阻力分布呈"单峰"形态,负摩阻力分布在桩身3～9 m的区域,其强度为-0.5～-2.2 kPa,较土体饱和条件下的数值明显偏小;天然状态和浸水状态下桩基承载能力差异较小,未浸水试桩的极限荷载是浸水条件下的1.06倍;但变形差异显著,浸水试桩在极限荷载下的变形是未浸水条件下的7.76倍。因此,建议在对应条件下可采用按沉降量控制的桩基设计方法。

The large scale field tests of filling piles were performed in a collapsible loess site（In the tests,the diameter and length of test piles are 0.8 m and 18 m respectively,the side length of immersion pit is 20 m）.The tests were performed under natural content and immersion state,of which the results were compared and analyzed.The results show that the influence depth of immersion is limited in the range from the surface to 8.5 m beneath the surface.The form of side friction curve is ＂single peak＂,the distribution of negative friction is 3~9 m from the top of the pile,the strength is-0.5^-2.2 kPa,the results are obviously smaller than the ones in the saturate condition.The difference of pile bearing capacity in the nature and immersion state is small,the bearing capacity in the nature state is 1.06 times of which in the immersion states,but the difference of the deformation is apparently,the deformation（at the maximum load） in the immersion state is 7.76 times of which in the nature state.So the deformation control method should be used in the corresponding conditions.1 tab,8 figs,11 refs.