群桩水平承载特性的现场试验研究及数值分析

Field experimental study and numerical analysis on horizontal bearing characteristics of pile group

本文设计了一套适用于现场试验的加载、测量和数据采集系统,分析水平荷载作用下群桩基础的受力情况以及周围土体的变形性状。同时,借助于PLAXIS 3D有限元分析软件对现场试验的群桩基础进行了数值模拟,将数值模拟结果与现场试验结果进行对比分析,验证了数值模拟结果的可靠性,并对水平受荷桩的承载性能做了进一步探讨。研究结果表明:在水平荷载作用下,桩身上部弯矩值较大且变化明显,对水平荷载作用较为敏感;桩身最大变形发生在桩顶,沿埋深增加其变形逐渐减小,桩周上部土体比下部土体较早进入塑性阶段;群桩基础中存在显著的群桩效应,各排桩受力不均匀,后排桩承担的荷载较大,前排桩承担的荷载较小;随荷载增加,群桩基础的影响范围越来越大,背荷面的影响范围远远大于受荷面的影响范围,加载方向的影响范围(5.9d~7.5d)明显大于正交于加载方向的影响范围(2.8d~3.9d),其中d为桩径。

A loading, measurement and data acquisition system suitable for field test was designed to analyze the stress of pile group foundations under horizontal load and the deformation behavior of surrounding soil in this paper. The finite element method(FEM) analysis software PLAXIS 3 D was used to simulate pile group foundations field test, and the numerical simulation results were analyzed and compared with the field test results to verify the reliability of simulation results, and the bearing characteristics under horizontal load were further discussed. According to the study results, under the horizontal load, the bending moment value of the upper of piles is large and changes are obvious, which suggests that piles are relatively sensitive to horizontal load;the maximum deformation of pile shaft occurs at the top of pile and the deformation gradually decreases with the increase of burial depth, and the upper soil around the pile enters the plastic stage earlier than the lower soil;there is a significant pile group effect, and the pile stress in each row is uneven that the pile load on rear row is greater than that on front row. With the load increases, the influence range of pile group becomes larger and larger, where the influence range in the loading-opposite side is much greater than that of the loading side, and the influence range in loading direction from 5.9d to 7.5d is obviously larger than that of piles perpendicular to the loading direction from 2.8d to 3.9d(d to be pile diameter).