【作者】 解家毕；

【导师】 刘祖德；

【作者基本信息】 武汉大学 ， 岩土工程， 2004， 博士

【摘要】 建筑物倾斜是软弱地基上一种常见的工程问题，它是由地基不均匀变形产生的基础倾斜而引起的。由于受计算理论和施工、监测技术的限制，历史上许多有名的建筑物都是由于得不到合理纠正措施，而不得不任其倒塌和倾斜，一个典型的例子就是意大利的比萨斜塔。纠偏技术的出现和兴起，一方面是由于土力学理论的发展、地基处理技术及相应施工机械与监测技术的进步而使这些技术的实现成为可能，另一方面是受与日俱增的客观需求分不开。但到目前为止，人们对倾斜建筑物的纠偏工作还只停留在工程经验上，纠偏技术还没有形成一个较系统的理论体系，这使得纠偏工作带有很大的盲目性。 实践表明，建筑物基础沉降不仅受外荷载的影响，而且在很大程度上还取决于地基、基础和上部结构三者的刚度。比较精确的分析方法是在计算中同时考虑三者的刚度贡献，即采用共同作用分析方法。共同作用分析要求上部结构、基础和地基满足在接触部位的变形协调条件。由于上部结构和基础不仅结构型式多样，而且它们的刚度比地基的大得多，这些因素都增加了共同作用分析的难度。多高层建筑物的倾斜分析及纠偏处理比常规基础分析还要复杂，倾斜分析及纠偏处理必然要把建筑物上部结构、基础和地基作为一个整体来考虑，分析各部分刚度对基础和地基的变形等的影响；此外，各种纠偏技术的理论研究也是一个急需解决的问题。本文围绕桩基础纠偏这一课题，对上部结构、桩基础和地基的共同作用分析方法进行了探讨，用所提出的分析方法对深厚软弱地基上地面大面积堆载作用下的桩基础和地基的变形形态及建筑物的倾斜进行了模拟，并对一些常用的纠偏方法的力学机理和适用条件进行了探讨，论文主要包括以下几方面： (1) 本文主要采用非线性有限元法进行求解。文中提出了简缩积分单元格式，以避免不可压缩或近似不可压缩材料在数值积分中出现体积锁死现象；采用多孔介质弹性和修正剑桥本构模型来模拟土体，并对修正剑桥本构模型进行了改进，以反应土体在张拉与压缩时的不同屈服强度特征；采用有限变形应变-位移模式反映实际情况中可能出现的大变形情况。 (2) 分析了不同施工工艺对灌注桩承载力的影响，由于不同施工工艺所得到的灌注桩的桩-土界面特征及桩端的条件相差很大，灌注桩的承载力可能相差很大，通过实测资料证实了不同施工工艺所得到的桩的承载力的差别；建立了桩-土共同作用分析的界面元模型，模型能很好地反映接触面的张开、闭合及滑移等复杂接触特性;通过对实测资料的模拟验证了模型的合理性。 (3)推导了子结构法及多级子结构法的刚度和荷载的凝集过程，对多高层建筑物上部结构的施工过程及刚度、荷载的形成过程进行有限元分析转化，建立了多高层建筑上部结构一基础一地基共同作用分析方法。 (4)采用无限元模拟远场区域土体的反应、用有限元模拟临近建筑物的土体反应，建立了深厚软弱地基上基础分析的无限元与有限元边界祸合分析方法。采用所建立的共同作用分析模型模拟分析了深厚软弱地基上桩基础附近地面大面积堆载情况下地基和桩基础的变形形态，以及超载对桩侧摩阻力的分布影响。在软弱土层较厚的情况下，由于深层土层的压缩变形较大，若不考虑深层土体的压缩，则得到的沉降值偏小，特别是在地面有较大超载作用时，深层土层的压缩量可能是决定建筑物倾斜的关键因素。 (5)对深层掏土纠偏法的工作机理进行了探讨。由于钻孔掏土和软弱土层向孔内挤淤的力学过程描述十分复杂，用数值分析方法也很难模拟这一过程。为了简化掏土过程，采用控制掏土孔壁节点位移的方法来模拟掏土时软弱土层向孔内挤淤的过程，对掏土后地基和基础沉降及桩侧的摩阻力的变化进行了分析，探讨了掏土纠偏法在桩基础纠偏中的适用性。计算表明，当深层土体向掏土孔内挤淤时，有部分桩侧摩阻力要转化为负摩阻力;但掏土段深度受土层的力学性质限制，一般较软的土层才有可能向掏土孔内移动，因此，掏土纠偏的效果也受土层的力学特性限制。 (6)对截桩纠偏法的工作机理进行了探讨，分析了承台底不同桩体的截除对纠偏效果的影响。由于不同桩体距形心主轴的距离不等，截桩的纠偏效果也是不同的，计算表明，距形心主轴较远桩体的截除的纠偏效果更明显一些。 (7)对考虑孔隙水压力一位移藕合下的上部结构一基础一地基共同作用分析方法进行了探讨，引出了在黄土、膨胀土地基情况下考虑非饱和流的共同作用分析课题。对于非饱和渗流孔隙水压力一位移祸合分析问题，本文采用单相流理论，忽略孔隙气压力的变化及其对土体变形的影响，以孔隙水饱和度和孔隙水压力作为状态变量，给出了非饱和土的应力状态表达式、渗流特性，建立了非饱和流孔隙水压力一位移藕合分析的有限元程式。 (8)采用饱和渗流孔隙水压力一位移祸合分析方法对建筑物的沉降和大面积堆载作用下的基础和地基的变形及建筑物的倾斜进行了模拟。 (9)对井点降水引起的地面沉降问题进行了探讨，采用非饱和流孔隙水压力一位移祸合分析方法对井点降水纠偏法进行模拟，对降水纠偏法在桩基础中的适用性进行了探讨。由于更多还原

【Abstract】 The deviation of building is a usual engineering incident of soft subgrade. It is caused by the leaning of foundation that is the result of the uneven deformation of subgrade. Because of the lack of theory and the limitation of construction and monitoring technic, many well-known constructions in the history have not been rectified up to now. A representative case is the leaning tower of Pisa. Some of them had collapsed. The springing up of deviation rectifying technic of building is a result of the development of the theory of soil mechanics and the improvement in foundation treatment, construction machinery and monitoring technic. Another cause is that there are so many leaning building today. By far, many deviation-rectifying measures are just resting on the experience of engineers. Little improvement has been done on the theory. This makes the work much arbitrary.Many engineering practices have proved that foundation settlement rests with not only external load but also mainly the stiffness of subgrade, foundation and superstructure. The much more accuracy analysis method is to take the three parts into account at the same time. This method is called interaction analysis method. The interaction analysis between superstructure, foundation and subgrade needs the three keeping continuity on the contact surface. Because of the diversified structural models of superstructure and foundation and the longing odds stiffness of the three parts, it is sophisticated to do so. It is more complicated to find the deviation causation of building than normal foundation design analysis. Say nothing of deviation rectifying. Superstructure, foundation and subgrade interact with each other and are in an indivisibility system. The effect of deviation rectifying is greatly influenced by the stiffness of superstructure and foundation. New theory needs to be established for this rising subject. This dissertation is about the interaction analysis method between superstructure, pile foundation and subgrade. It deals mainly with the incline analysis and deviation rectifying method of a high building resting on thick and soft soil.The major content of this dissertation is as follows:(1) It uses nonlinear finite element method to take the three parts of building into account. A reduced integration element is developed to avoid volumetric locking when the material behavior is (almost) incompressible. The constitutive model of soil is an extension of the Modified Cambridge Clay Model. The extension version can depict the different yield character of soil under tension and compression. And it uses porous elastic model toexpress the relation of stress and strain before plasticity. Finite deformation formulation is used to describe the deformation of material.(2) It probes into with the influence of ultimate capacity of single pile that is poured by different construction technics. Because the contact performance of soil and piles lies mainly on the construction technics. The range of variation of ultimate capacity of single pile is great. A contact interaction model is developed to simulate the interaction between pile and soil. The contact model can simulate easily the closing, opening and slipping between two surfaces. It uses the contact model to study the affecting "factor of ultimate capacity of single pile poured by the construction technics.(3) The derivation of the stiffness development of superstructure and multilevel superstructure is given out; this derivation process can be used to simulate the construction process of building. The substructuring method is used to take the stiffness of superstructure into account in interaction analysis of foundation.(4) Infinite element is developed to consider the effect of far field, and the vicinity field of foundation it uses finite element. Finite elements and infinite elements must satisfy deformation continuity at joined position. An engineering example is analyzed using the interaction method developed in this dissertation. The deformation of soil and piles is sim更多还原