基于桩身材料统计损伤的基桩稳定性分析方法研究

This program explores the pile buckling stability analysis method based on pile material damage under varied conditions through several ways such as model tests, numerical simulation and theoretical analysis, etc. Firstly, the statistical damage constitutive model describing the damage characteristics of pile material is built according to pile material property tests considering initial defection conditions. Meanwhile, statistical parameters included in the model are inversed from experimental results. Secondly, the model piles are made from concrete incorporated with air-entraining agent. Then, the laboratory model test plans are designed based on orthogonal tests. Thus, the loading-transfer mechanism, the buckling development laws of the whole pile structure system and failure mode are obtained. On the other hand, numerical simulations are carried out to obtain the effect of several influence factors, such as initial defects, pile material, size, etc., on the critical buckling load of piles and stable calculated length. Then, the total potential energy equation of pile-soil system is derived on the basis of statistical damage constitutive model considering pile material damage and the homotopy analysis method is adopted to get the solution. Finally, a set of design method of the buckling stability of piles considering the damage characteristics of pile material are put forward on the basis of model tests, simulations tests and theoretical research results.

本项目通过室内模型试验、数值模拟试验及理论分析等方式，探讨不同工况下基于桩身材料损伤的基桩屈曲稳定性分析方法。首先，通过考虑不同初始缺陷条件的桩身材料性质试验，结合连续介质的损伤理论建立描述桩身材料损伤特性的统计损伤本构模型，并根据实测结果反演模型中包含的统计参数。其次，用混凝土掺入引气剂制作模型桩，基于正交试验设计理论制定室内模型试验方案，研究模型桩荷载传递机理、桩身结构体系的屈曲变形发展规律以及破坏模式。与此同时，开展数值模拟试验，得到初始缺陷、桩材、尺寸等对基桩屈曲临界荷载及稳定计算长度的影响。然后，基于考虑桩身材料损伤的统计损伤本构模型，建立考虑桩身材料损伤的桩土体系总势能方程，并利用同伦分析方法求解。最后，综合模型试验、数值模拟及理论研究成果，提出一套考虑桩身材料损伤特性的基桩屈曲稳定性设计计算方法。

为解决处于高山、边坡等复杂地形地貌处基桩的承载机理、变形特性及破坏模式等屈曲稳定性问题，本项目采用室内试验、理论模型计算、数值分析等手段对该问题进行了深入系统地研究。其中，采用室内模型试验，探究了斜坡效应对基桩屈曲稳定性及屈曲失稳破坏模式的影响规律，并通过试验数据拟合得到了斜坡基桩屈曲临界荷载计算公式；理论研究方面，基于能量法和突变理论，并结合统计损伤理论，将桥梁桩基简化为单桩模型，以某工程实例建立计算模型，同时考虑斜坡效应及界面摩阻效应的影响，得到了陡坡段桥梁桩基临界荷载和计算长度，并通过算例验证其合理性；数值研究方面，通过ADINA和ABAQUS大型有限元数值计算平台，探究了影响基桩屈曲稳定的主要因素，并通过与理论计算结果的对比，进一步验证了理论计算方法的合理性。综上所述，本项目的研究成果可对相关工程中的基桩屈曲稳定性设计提供相应的参考，进一步提高工程中基桩的经济性、耐久性及安全性。