加载次序对湿陷性黄土中基桩承载力检测的影响  

Influences of loading sequences on bearing capacity test of piles in collapsible loess

作　　者：夏力农[1,2] 苗云东[2] 刘小平[1] 

机构地区：[1]长沙学院土木工程系,长沙410003 [2]湘潭大学土木工程与力学学院,湘潭411100

出　　处：《岩土力学》2009年第S2期318-322,共5页Rock and Soil Mechanics

摘　　要：湿陷性黄土地区基桩承载力检测中桩顶荷载是在土体沉降后施加的,桩基使用条件下是桩顶荷载施加之后再出现土体沉降。简要分析了这两种加载次序之间桩土相互作用差异的机制。采用有限元方法分析了这种差异。计算结果表明,在这两种加载次序中,桩顶荷载的增加都会引起沉降增加,中性点下降,下拉力减小。结果还表明,与桩顶荷载先施加的相比,桩顶荷载后施加得到的中性点的位置比较低,桩基沉降比较小,下拽力也较小,这些差异随着桩顶荷载的增大而更加明显。在两种加载次序的各个加载阶段,桩周摩阻力的分布与发挥也会出现细微的变化。这会使湿陷性黄土地区桩的承载力检测结果略微偏于不安全。Load on pile top is acted after the settlement of soil surrounding the pile in bearing capacity test of piles in collapsible loess,and it is acted before the settlement of soil on general working condition of pile foundation.Different mechanisms of pile-soil interaction between such two loading sequences are simply analysed.Finite element method is used to calculate the differences.Analysis results show that settlement of pile increases,neutral point goes down and dragload induced by negative skin friction reduces as the load on pile top increases in both loading sequences.It also shows that comparing with load on pile top acted before in general working condition,loading sequence of bearing capacity test in collapsible loess would make the neutral point position in pile lower,settlement of pile smaller and the dragload in pile smaller.The differences of neutral point position,settlement and dragload in the two loading sequences increase gradually as working load increases.At every stage in both loading sequences,there exists small differences on distribution and development of skin friction along the piles.This will cause the testing result of bearing capacity of piles relatively unsafe in collapsible loess zone.

关 键 词：湿陷性黄土 桩 承载力检测 负摩阻力 加载次序 

分 类 号：TU444[建筑科学—岩土工程]