建筑物精确掏土纠倾设计的孔周土应力和变形特性

At present, the building rectification is short of theoretical research. The proposal take the under-excavation (watering) rectifying method as an example. From theoretical and experimental studies, the soil plasticity zone evolution mode and the deformation property around the excavation hole will be illustrated, so the precise under-excavation rectifying design method will be established. The main research including: (1) To establish the typical site data base through exploring and the random field model of the site soil is obtained. Take the soften model to simulate the failure of the soil, the whole rectification process analysis are done which considering the superstructure-ground interaction. And the plastic evolution rule and deformation properties around the excavation zone are studied. (2) Based on the soil plastic mechanics and strength theory, the shape of the plastic zone is studied and the plastic radius is deduced under the non-uniform stress state. The relationship equation between the excavation radius and stress from foundation is established. The influence of some key parameters to the rectifying results and speed such as excavation hole separation distance and its distance to the foundation are studied. (3) The model and site experiment are carried out to simulate the yield and failure mechanisms around the excavation hole and compare the results with the theoretical study. So the precise design method for under-excavation rectifying method is established and provide theoretical support to the rectifying engineering projects.

目前建（构）筑物纠倾理论研究不足。项目以掏土（灌水）纠倾为例，从理论及试验两方面，揭示土体塑性区演化模式及孔周土变形特性，建立精确掏土纠倾设计方法。研究主要有：(1)建立典型地基现场勘探数据库，构建地基土随机场模型，以土体软化模型模拟土体失效，进行上部结构-地基共同作用下掏土（灌水）纠倾全过程分析，研究掏土区土体塑性区演化规律及变形特性。（2）基于土体塑性力学强度理论，研究非均匀应力场条件下，掏土孔周边非圆形塑性区形状，求得塑性区尺寸的解析解，建立掏土孔半径与基底应力关系方程，研究掏土孔间距及与基底距离等关键参数对纠倾效果和回倾速度的影响。（3）采用模型箱及原位场地相结合进行掏土（灌水）纠倾试验，研究掏土孔的屈服及塌孔破坏机制，并与理论分析结果进行对比，从而建立精确掏土纠倾设计方法，为掏土纠倾工程提供理论支撑。

地基承载力不足或上部结构荷载不均匀等原因，建筑物出现倾斜情况，大多数可通过纠倾技术回正从而正常使用。建（构）筑物的纠倾方法有抬升法、迫降法以及二者的混合应用。迫降方法中的掏土纠倾法在建（构）筑物纠倾工程中的应用最为广泛，其受力机理也颇为复杂，理论研究明显不足，本项目主要针对掏土法进行研究。研究掏土纠倾法孔周土塑性区发展演化规律、掏土孔破坏机制及掏土纠倾的精确设计方法，从而解决纠倾工程的设计及实施以工程经验为主，工程风险高的问题，特别是近年来出现了体型巨大的高层建筑及整体性差的历史建筑（包括文物建筑）的纠倾工程，对纠倾技术提出了更高的要求。.本项目通过掏土纠倾试验、数值分析、解析方法等方面深入探讨了掏土纠倾法的掏土孔破坏机制、掏土影响范围及掏土孔塑性区半径等问题。主要研究结论如下：（1）采用模型箱试验进行了三种不同掏土孔间距的掏土纠倾试验，研究掏土孔的屈服及塌孔破坏机制，得到了掏土孔的三种破坏模式：立式椭圆形破坏、卧式椭圆破坏及近似圆形破坏。掏土孔周边土体发生土压力转移，土压力从孔上部转移至孔侧土体，说明有土拱效应形成，可通过孔侧土压力达到破坏状态确定建议孔间距。（2）采用有限元分析手段，对掏土孔周边应力及变形进行了分析，并得到了掏土孔的影响范围，通过影响范围的贯通，从而确定最大的掏土孔间距，从而实现掏土纠倾设计提供依据。（3）基于土体塑性力学强度理论，研究非均匀应力场条件下，掏土孔周边非圆形塑性区形状，得到了掏土区土体塑性区演化规律及变形特性，提出了掏土孔塑性区半径计算公式。（4）对顶升纠倾法也进行了一些初步研究，阐明了顶升纠倾法的整套技术体系，并重点研究了托换结构刚度变化对上部结构受力和变形的影响。