溶洞地区桩基础应力扩散角的影响因素数值分析

Numerical Analysis of Factors Influencing Stress Spread Angle of Pile Foundation in Karst Cave Area

岩溶地区修建变电站,当基础下有较大规模的溶洞且分布位置较浅时,会对工程的设计、施工及运营等产生很大的影响。现行对岩溶地区桩基础稳定性分析的方法主要有:定性评价法、半定量评价法、定量评价法;其存在依赖工作者工程经验、分析方法适用性不强,分析理论方法不完备等不足。有限元数值分析法是一种十分成熟的数值分析方法,与其他方法相比它几乎适用于所有的计算领域,具有适用性强、处理非均质、非线性、复杂边界问题方便等突出优点。应用有限元分析软件,模拟在随机分布的岩溶地基情况下桩底竖向应力扩散角的情况,并分别分析了溶洞跨度、顶板厚度、桩宽对桩底应力扩散角的影响。分析结果表明桩底竖向应力扩散角随着溶洞跨度的增加而扩大,随着顶板厚度的增加而减小,随着桩宽的增加而先减小后扩大再减小的变化规律。

In the case of the pile of power transmission tower in karst area,if there is a large scale of karst cave and its distribution position are shallow, it will have a great influence on both design, construction and operation of the tower and the whole project. The existing methods for stability analysis of pile foundations in karst areas includes qualitative evaluation, semi-quantitative evaluation and quantitative evaluation. Those methods are either dependent on workers＇ engineering experience, or using analytical methods that are lack of applicability, or using analysis theories and methods that are incomplete. Finite element numerical analysis is a very mature method of numerical analysis. Compared with other methods, it is almost applicable to all fields of calculation. It has the advantages of strong applicability and easy to deal with nonhomogeneous, nonlinear and complex boundary problems.In this paper, finite element analysis software is applied to simulate the vertical stress distribution of the base at the bottom of the pile under random distribution of karst foundation. The influence of cave span, roof thickness and pile width on the vertical stress distribution of the base at the bottom of the pile is analyzed respectively. The analysis results show that the affected area of vertical stress distribution of the base at the bottom of the pile increases with the increase of the span of the cave,decreases with the increase of the thickness of the roof, and decreases first and then increase and then decreases with the increase of the pile width.