非饱和黄土的强度特性及非线性本构模型研究

【作者】 王朝阳；

【导师】 倪万魁；

【作者基本信息】 长安大学 ， 地质工程， 2004， 硕士

【摘要】 本文以非饱和黄土为研究对象，以直剪、非饱和土三轴试验和CT试验为手段，对非饱和黄土的抗剪强度、结构强度特性及变形、损伤演化过程、土体孔隙的扩展等特性进行了系统的试验研究和深入的理论分析，并在此基础之上建立了非饱和土的非线性损伤本构模型。 首先，对非饱和黄土进行了土的吸力测试、抗剪强度试验、结构强度和非饱和土三轴试验。用非饱和土的抗剪强度公式与饱和土抗剪强度公式求得的数值进行了比较，指出用非饱和土力学的强度参数更接近于实际，对工程建设有一定的指导意义。在试验的基础之上，对非饱和Q₃黄土的结构强度进行了研究，提出了用土的结构强度表示土体抗剪强度的表达式，为计算非饱和土的抗剪强度提供了一种简便实用的方法。应用非饱和土三轴仪，对非饱和黄土进行了控制吸力的三轴试验，在试验的基础之上，建立了非饱和黄土的非线性模型。该模型参数确定简单，模型中参数都有确定的物理意义，是邓肯—张模型的推广。 其次，应用非饱和黄土的三轴CT扫描仪，进行了原状Q₃、Q₂黄土的三轴试验过程的动态、定量、无损的CT扫描，结合CT图像、数据与应力应变关系，对非饱和黄土的剪切过程分4个阶段进行了深入分析研究。提出了非饱和黄土的初始损伤应力和应变门槛值的确定方法，并且定义了基于CT数的损伤变量。这一工作为非饱和黄土损伤本构关系的研究奠定了基础，具有非常重要的意义。 最后，以复合体损伤理论为基础，提出了非饱和黄土的非线性损伤本构模型，该模型包含13个变形参数，都可由试验测定，可全面地反映原状非饱和黄土的力学特性，为损伤力学在土体工程中的应用开辟了新的途径。首次将CT的损伤检测数据应用于损伤模型中，是对CT无损检测技术在土体损伤模型中应用的一个尝试。更多还原

【Abstract】 Focused on the unsaturated loess, the characteristics of the unsaturated loess such as shear strength, structural strength, deformation, damage evolution, porosity evolution were scheduled systematic experimental study and deep theory analysis in this paper by means of direct shear, unsaturated triaxial tests and computerized tomography. According to the above test results, a nonlinear damage constitutive model of unsaturated soil was developed.Firstly, a series of unsaturated loess tests were carried out under matric suction testing, shear strength, structural strength, unsaturated triaxial tests. In the trial above the foundation, the numerical value that the shearing strength formula with unsaturated soil was obtained with the saturated soil shearing strength formula had carried on the comparison, and points out with the unsaturated soil strength parameter more is close to in reality, and the construction have the fixed guidance meaning to the engineering. According to the research of the structural strength of unsaturated Q3’s loess, this paper put forward with shearing strength by expressed with structural strength, for the shearing strength of unsaturated soil of calculation has provided one kind of simple and convenient practical method. Apply three apparatuses in the unsaturated soil, and has carried on three trials of control suction, and has built the nonlinear model of unsaturated loess above the foundation of trial to unsaturated loess. This model parameter is defined simply, and the parameter all has definite physics meaning in the model, is Duncan -zhang model generalization.Secondly, with a triaxial test instrument for unsaturated loess which can work with computerized tomograph carried original Q3 and Q2 loess testing on instantaneously, quantificationally and undamaged scanning. Combining CT images, data and stress-strain curve, this paper divided shearing process into 4 period with respectively analyzing studying. The author has put forward how to decided initial damage stress and strain threshold value of the unsaturated loess and defined damage variable by CT’s number. This work has established the foundation for the damage constitutive model of the unsaturated loess, which has the very important meaning.Finally, based on the composite damage theory, this paper suggested a nonlinear damage constitutive model of unsaturated loess, which include 13 deformed the parameter by testing. This model can reflect the mechanics property of unsaturated loess of original state completely, and opened up the new way for damage mechanics the application in the soil engineering aspect. This thesis applied the damage data testing by CT machine to the damage model for the first time, which is a try that the undamaged CT technique used to the damage constitutive model.更多还原