浸水及固结过程对湿陷性黄土桩基力学特性影响的机理分析

依托兰州南绕城高速公路项目,通过模拟该地区年降雨量的实际情况在自重湿陷性黄土场地上进行现场浸水载荷试验。设置了桩基在自重无荷载情况下浸水和浸水完成后在土体固结过程中对其进行加卸载这两种工况。实验结果表明,在模拟两次非连续性降雨情况下,桩在自重湿陷时负摩阻力的变化值较小并且其影响范围在地表以下7 m左右。由于在整个实验过程中负摩阻力均出现多峰值状态,从而出现多个中性点,为便于设计者设计施工,提出等效中性点概念,等效中性点位于桩的0.257~0.40桩长范围内。而等效中性点的位置比《建筑桩基技术规范》给出的参考值范围小很多,可为以后兰州地区桩基设计提供参考。

Mechanism Analysis of Influence of Immersion and Consolidation Process on Mechanical Properties of Collapsible Loess Pile Foundation

Based on Lanzhou South Ring Highway project,the field tests of piles were performed in a collapsible loess site by simulating the actual situation of the area"s annual rainfall.The tests were performed under pile load-free immersion state and in the consolidation process of loading and uninstalling test.The results show that the pile"s negative friction in the self-weight collapsible change value smaller and it"s sphere of influence in the 7M below the surface by simulating two discontinuity rainfall. There appear multiple peaks due to negative frictional resistance throughout the process of test, leading to more neutral points, for ease of design and construction, proposed the concept of equivalent neutral point.Equivalent neutral points are in the range of 0.257 to 0.40 times of the pile length.The locations of equivalent neutral points are smaller than the range proposed by <>.The results can provide references for the later design of pile foundation in Lanzhou area.