【作者】 周海林；

【导师】 刘宝琛； 王星华；

【作者基本信息】 中南大学 ， 道路与铁道工程， 2002， 博士

【摘要】 振动注浆是处理软弱地基的一种新的施工方法，该方法首先通过振动机具的冲击振动，在砂土地基内形成软化区，然后利用注浆管将浆液压入砂土中。在该施工工艺中，振动是取得较好施工效果的关键技术之一。本文着重进行振动力作用下饱和砂土地基的响应分析，从有限元计算、解析分析和工程经验三个角度进行研究，三种方法各有优缺、互为补充，以期为施工工艺提供良好的施工参数。 本文首先采用目前国内较先进的微机控制动三轴仪，利用其可以适时采集和储存数据的优势，对砂土的实验过程进行了细致的分析，研究该过程中孔隙水压力发展、轴向应变发展以及它们与应力路径之间的关系，对饱和砂土的剪胀、剪缩和卸载体缩等多个方面进行了研究，探索了砂土的动力特性，分析了影响砂土抗剪强度的各种因素，这些因素既包括土本身的特性(土的密度、结构、级配、透水性以及初始状态等)，又包括动荷载的特征(振动力幅值大小和振动频率等)。这些试验成果为有限元计算提供参数和为动本构模型的选取和改进提供依据。 本文得到一个饱和砂土的动本构模型，该模型可以综合考虑广义塑性模型与粘弹性模型的优点，并且计算简单，可以较好地反映饱和砂土的动力特性。该模型借鉴了散粒体模型的计算思路，利用广义塑性模型中的一些简化计算概念，形成了自己的计算模式，能较好地反映四个特征区域的应力应变关系和试验当中出现的剪胀和剪缩现象。本文同时介绍了该饱和砂土动本构模型的参数选取，并利用已有的动三轴实验数据对该模型进行验证。 本文使用变分法推导出竖向点振源作用下饱和地基的u-w型有限元运动方程，该方程因考虑了孔隙水的可压缩性，在计算中可以得到孔隙水压力。并在推导过程中得出了用有限元格式表达的能量方程。对于砂土在进入到破坏阶段，往往伴随着大应变的出现，已有的小应变理论已经不能满足工程计算的要求，本文在以上分析得到的能量方程的基础上，利用虚功原理推导出在振动力作用下的大应变有限元方程，并得到合理的数值解。考虑到反射波在计算区域内经多次反射、透射和散射对计算结果可能产生较大的影响，在上述饱和砂土有限元模型的基础上，建立了一种新的动力无限元计算模型，该模型能满足工程计算的要求。 本文编制了动力分析程序YEHUA．FOR以及配套的静力非线性程序和基频计算程序，这些程序是以饱和砂土振动理论为基础，结合我院杨果林博士原有的塑性动力分析程序编制而成。该程序通过合适的数据读入语句，可以利用目前使用较为广泛的通用程序中的可视化窗口进行前处理，读入其生成的数据文件，使得数据输入大为直观和简化。该程序可以求解饱和砂土连续介质，包 博士学位论文括岩土、隧道与地下结构物在平面应力、平面应变和轴对称情况下的非线性瞬时动态问题。利用该计算程序，结合一个算例进行分析，得到了在不同振动力幅值、振动频率下饱和砂土的响应，以及在振动作用过程中，饱和砂土内的孔隙水压力的发展过程和软化区域的扩展过程。 本文采用可压缩多孔介质模型，引用了流体饱和两相多孔介质的动力控制方程，利用传递矩阵方法，借鉴有限元思想进行耦合计算，获得了在半空间饱和砂土一定埋深处施加竖向动荷载问题的Laplace－Hankel变换解，并将该解数值化。基于连续介质力学的混合物理论建立的多孔介质理论和动力控制方程，假设砂土满足各向同性并处于弹性小应变状态，竖向振动力将在饱和砂土内部产生三种波，分析了这些波的弥散曲线和特征衰减曲线，从波传播的角度，研究了振动力参数和土性参数对振动范围的影响。 根据砂土在振动力作用下可能发生液化和液化程度具有模糊性的特点，利用模糊逻辑和神经网络的互补技术，形成具有很强非线性映射和自适应学习功能的专家预测系统一模糊神经网络。该网络是一种前向多层网络，它把传统的模糊逻辑控制器的基本元件和功能与具有分布学习能力的连接式组合到结构中，输入和输出节点分别代表输入状态和输出状态及预测。本文利用 Matlab中 FZZZy具箱编程，通过有限的实验数据和输入专家知识对该系统进行训练，可以解诀砂土液化的预测难题，算例的检测结果表明其效果较好。可以利用该系统从工程经验角度研究振动力参数和土性参数对振动效果的影响。更多还原

【Abstract】 Vibrating grouting method is a new way to treat weak foundation. The sand of foundation is made destructive by vibrating load at first, and as a result its strength is weakened in this destructive area. Under the condition of high pressure, the grout is easier to be poured into the foundation. From what is said above, we know that vibration is important to the grouting method. In this paper, the author studies the sand response under the vibrating load carefully to provide the vibrating grouting method with good parameters.At first, the sand is studied through the dynamic tri-axial experiment, in which we use a computer-controlled system which is advanced in our country. With the data recorded by computer, the author studies the experiment progress in detail, which includes the development of pore press, strain, strength of the sand, etc. Connecting the development of these phenomena with the development of stress path, the author finds new mechanism which can explain the phenomena in the experiment. What is more, according to the dynamic test of the sand, there appears a steady state at the last phase of the development of strain and stress path, in which the strength of the sand is studied because it is an important parameter in evaluating the stability of sand against liquefaction.Secondly, the dynamic constitutive relation was studied through the dynamic tri-axial test. According to the different behavior of stress status in the experiment, the progress is divided into four phases. A new sand constitutive relation connecting the relationship between stress and strain with the stress path is set up to reflect these phases, at the same time the phenomenon of shear contraction, shear dilatation and unloading shrink are taken into account in this constitutive relation. Extracting the merit of the nonlinear model and plastic-elastic model, it is simple and effective. The computation results show that the dynamic constitutive relation can reflect most of the phenomena in the process of experiment . Thirdly, because there is local large deformation in the sand breakage under vibrating load in the destructive phase, small deformation theory is not appropriate; therefore, large deformation analysis theory is applied to this process. Based on the research of many predecessors, the author sets up a computation pattern of the saturated sand deduced from energy theory. In this pattern a new kind of infinite boundary element is developed to reduce wave reflection on the boundary. By this method, a simple and convenient numerical way is worked out and dissipation of the pore press, damping can be taken into account. It can not only solve the problem of material nonlinearity, but also be suitable for the problem of large deformation.Based on the work of Dr. Yang Guolin, a finite element program is worked out according to the finite element theory. The data to be imputed can be generated by software Super-Sap93, which can simplify the work of data preparation. In this program, the material nonlinearity and geometry nonlinearity are taken into account; what is more, it can calculate two-dimensional stress, strain and axial symmetry problems of foundation, tunnel, etc. Aftercontrasting tri-axial experiment data with the computational result of the program, we can see that the program works well.Fourthly, with the finite element program, the author analyzes the relationship between the load magnitude or frequency and range of breakage or pore pressure. This can provide appropriate parameters for the method of vibrating grouting.Fifthly, adopting the compressible porous medium, the author adduced dynamic theory of liquid saturated porous medium to analyze the displacement and force in the sand when there is dynamic load below the earth surface. Supposed to be axial symmetry, the problem is put into the cylindrical coordinate, and through the Laplace-Hankel transformation, the equations are turn into differentia equations of constant coefficient. In the analyzing progress, dynamic transfer matrix is used t更多还原