边坡泥化夹层宏细观参数关系及应变软化本构特性研究

发布时间：2018-12-22 08:15

【摘要】：软弱夹层的存在是引起顺层边坡失稳破坏的关键性因素之一,而泥化夹层作为最常见的次生型软弱夹层,抗剪强度指标极低,常常是导致斜坡失稳的主控因素。泥化夹层的核心问题是强度问题,然而,在具体的工程应用当中存在一个普遍的问题,即当工程实际中层间泥化夹层厚度较薄时,难以通过室内常规直剪试验或三轴压缩试验来获取其强度指标。为解决这一实际工程问题,论文拟从泥化夹层细观结构出发,结合室内单轴压缩试验及数字散斑变形测量技术,获取其压缩变形特性及破坏特征,然后采用离散元方法建立泥化夹层数值模型,研究其应变软化本构特征,并对其强度进行预测。具体的研究内容包括以下几个方面： (1)通过SEM电镜扫描对泥化夹层原状样进行细观扫描,结合阈值分割技术对扫描图片进行二值化处理,然后利用matlab统计分析对其细观结构进行量化,主要获取了后续离散元建模过程中所需的泥化夹层孔隙率。 (2)采用数字散斑成像技监测记录泥化夹层单轴压缩试验过程中的变形破坏机制,并利用应变破坏准则和土力学中土的极限平衡条件研究获得泥化夹层的剪切强度特征。 (3)利用PFC颗粒流程序语言,建立泥化夹层离散元模型,分别对数值单轴压缩试验及直接剪切试验进行了参数敏感性分析,主要研究了颗粒刚度、颗粒间摩擦系数、接触粘结强度、竖向应力、加载速率等因素对数值试样应力应变本构关系的影响。结合室内单轴压缩试验的结果对泥化夹层颗粒流模型中的细观力学参数进行了标定,得到比较能真实反映泥化夹层真实状态和力学性能的数值模型。 (4)利用数值直接剪切试验和反复剪切试验对泥化夹层剪切破坏细观机制及其应变软化特性进行较为深入的研究,并对其峰残强度参数进行预测。随着西部大开发步伐的大力推进和西部山区公路的大量修建,泥化夹层可能导致的路基边坡稳定性问题日益突出,本论文研究旨在为实际工程中的边坡稳定性评价提供参数依据。
[Abstract]:The existence of weak intercalation is one of the key factors leading to the instability of bedding slope. As the most common secondary weak interlayer, the shear strength index is very low, which is often the main controlling factor of slope instability. The core problem of mud interlayer is strength problem. However, there is a general problem in concrete engineering application, that is, when the thickness of clay interlayer is thin in engineering practice, It is difficult to obtain the strength index by conventional direct shear test or triaxial compression test. In order to solve this practical engineering problem, this paper intends to obtain the compression deformation characteristics and failure characteristics of the mudded sandwich mesoscopic structure, combined with indoor uniaxial compression test and digital speckle deformation measurement technology. Then the numerical model of mudded intercalation is established by discrete element method. The constitutive characteristics of strain softening are studied and its strength is predicted. The specific research contents include the following aspects: (1) Meso-scanning of mudded interlayer raw samples by SEM scanning electron microscope, and binarization processing of scanned images with threshold segmentation technology, Then the meso-structure was quantified by matlab statistical analysis, and the porosity of mudded intercalation was obtained in the process of subsequent discrete element modeling. (2) the deformation and failure mechanism of mudded interlayer during uniaxial compression test is recorded by digital speckle imaging, and the shear strength characteristics of mudded interlayer are obtained by using strain failure criterion and limit equilibrium condition of soil in soil mechanics. (3) based on the PFC program language, a discrete element model of mudded intercalation is established, and the parameter sensitivity of numerical uniaxial compression test and direct shear test are analyzed respectively. The stiffness of particles and the friction coefficient between particles are studied. The influence of contact bond strength, vertical stress and loading rate on the stress-strain constitutive relationship of numerical specimens. Combined with the results of laboratory uniaxial compression tests, the meso-mechanical parameters of the mudded interlayer particle flow model are calibrated, and a numerical model which can truly reflect the true state and mechanical properties of the mudded interlayer is obtained. (4) using numerical direct shear test and repeated shear test, the meso-mechanism of shear failure and strain softening characteristics of mudded intercalation were studied, and the peak and residual strength parameters were predicted. With the rapid development of the western region and the construction of a large number of highways in the western mountainous areas, the stability of the subgrade slope caused by the mud intercalation may become increasingly prominent. The purpose of this paper is to provide parameter basis for slope stability evaluation in practical engineering.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU43

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