摘要
对群桩基础工作性能的研究一直是岩土工程领域的一个热点,但由于群桩基础无法进行现场载荷试验,而实验室模型试验又很难模拟群桩工作的实际状态,因此数值模拟分析方法的研究是十分必要的。本文首先回顾了以往的一些研究竖向荷载作用下群桩工作性状的方法,并对国内外的研究现状作了深入细致的研究。在此基础上,对单桩和群桩的工作性状做出了比较明确的阐述。然后介绍了ANSYS有限元程序的模拟方法,即采用三维实体建模的方法;采用ANSYS有限元程序中SOLID45单元对桩体、土体进行单元划分;在桩—土界面上采用ANSYS有限元程序提供的Targe170和Conta174单元来模拟接触面的力学性能;通过使用ANSYS有限元程序中的DP模型来模拟土的非线性。最后通过模拟分析得到群桩荷载—位移曲线及相应有关数据,通过对这些数据的分析来研究群桩基础的工作性状,并对某工程实例和模型试验的结果加以分析对比,说明ANSYS有限元程序能够很好的模拟群桩的工作性状。
本文研究了群桩的几何特性,主要指桩数、桩距、承台对于竖向荷载作用下群桩的受力性能的影响,从中总结出群桩的几何特性在何种状态下更有利于发挥承载能力,此外,论文还研究了群桩基础的承台效应、侧阻效应、端阻效应以及群桩基础的破坏模式、破坏特征及承载能力,以达到更加安全、经济的目的。
Research on the effect of pile-group foundation is a focus all along in geotechnical engineering. However, since the field prototype test of pile-group foundation is impossible, it is of necessity to research by numerical simulation method.
Performance of pile-group is simulated by ANSYS FEM (Finite Element Method) program in this paper. Previous methods to study performance of pile- group under vertical loads are reviewed and present research development in and out of China is discussed in detail. Based on the above work, performances of single pile and pile-group foundation are clearly stated. The simulation method of ANSYS FEM program id introduced, that is, three-dimensional solid modeling method. Pile and soil are discretized into SOLID45 elements in ANSYS FEM program. On pile-soil interface, mechanics properties of contact surface are simulated by Targe170 and Conta174 Elements provided by ANSYS FEM program. Soil nonlinearity is simulated by DP model in ANSYS FEM program. Finally, load-displacement curves of pile group and related data are obtained by simulation analysis. Performance of pile-group foundation is studied by analyzing the calculated results. Compared with an engineering example and model test results, the ANSYS FEM program can well simulate performance of pile group.
The research in this paper is to study the influence of geometry properties mainly about pile number、pile diameter、cap size on vertical load behavior of pile-group. By comparison with vertical load behavior of single pile and pile with cap, the state in which the geometry properties of pile group are more advantageous to develop bearing capacity is concluded to obtain a safer and more economical design.
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