竖向荷载作用下倾斜桩的荷载传递性状及承载力研究

Load transfer and bearing capacity of inclined pile under vertical load

桩基可能会因各种原因导致桩体发生倾斜,桩身的垂直度往往超过《建筑桩基技术规范》的允许值,如何确定这些倾斜程度并不很大的倾斜桩的承载力一直是工程实践中的难题。对天津某高层建筑工程不同垂直度的倾斜桩进行了现场载荷试验,试验结果表明小倾斜度下桩的承载力并不一定下降。在试验成果基础上利用有限元分析软件ABAQUS进行模拟,分析了不同垂直度、不同土质条件下桩的荷载传递及承载力受垂直度变化的规律。有限元分析结果表明,当桩的垂直度不大于4%时,当桩身具有足够的抗弯强度和刚度时,相同荷载下其沉降反而小于竖直桩,但会在桩身产生一定的弯矩,桩顶自由的单桩也会产生一定水平位移。承台有助于减小倾斜桩的水平位移与挠曲。

Inclination of piles may occur due to different reasons.Most inclinations of piles are beyond the limitation imposed by the Technical Code for Building Pile Foundations（JGJ94—94）.How to determine the bearing capacity of inclined piles is a tough problem in practice.Field load tests on 6 inclined piles with different degrees of inclination were performed and their bearing capacities were compared.It was shown by test results that the bearing capacity did not necessarily decrease when the degree of inclination decreases if the inclination was within a small range.Based on modeling one of the load-test results of inclined piles,the required characteristics of soil for FEM analysis were obtained to conduct numerical analysis.The load transfer and bearing capacity of piles with different degrees of inclination under different soil conditions were studied.It was shown by numerical analysis that under the same vertical load the settlement of piles with the degree of inclination no more than 4 percent was even smaller than that of a vertical pile,but comparatively large bending moment would be produced,thus for inclined pile,enough rigidity and strength were required to resist these bending moment and lateral displacement.Lateral displacement and bending of inclined pile could be reduced with the introduction of pile cap.