汉中地区膨胀土工程特性及其滑坡变形机理基研究

发布时间：2018-01-28 00:04

本文关键词： 非饱和膨胀土降雨作用滑坡裂隙锚杆框架梁系统　出处：《西南交通大学》2014年博士论文　论文类型：学位论文

【摘要】：膨胀土作为一种特殊性质的土体,具有随着含水量不断变化表现出显著的吸水膨胀、失水收缩、浸水后承载力较大幅度衰减的特征。这些有别于其它类别土体的工程地质特性,使得其所组成的路堑边坡也呈现出特定的稳定性能。论文以十天高速陕西汉中勉县境内的武侯服务区附近膨胀土路堑边坡为研究对象,采用室内试验、理论分析、计算程序开发以及数值模拟等综合手段,较为深入的掌握了该地区膨胀土的基本特性,进而开展了考虑裂隙影响的降雨诱发膨胀土滑坡变形机理、预警性降雨阈值以及膨胀土滑坡防护措施的研究工作,取得了以下几个方面的研究成果和主要认识：(1)通过瞬态水力特性循环试验,得到了不同水力路径条件下汉中地区膨胀土的土-水特征函数曲线(SWCC),并基于该曲线数据推导得到了相应的渗透系数特征函数曲线(HCF)。试验结果表明,处于不同水力路径进程中的同一类型膨胀土,会呈现出差异明显的水力学特性,也即具有明显的“滞后效应”。从微观结构入手,探究了孔隙水赋存及渗流形式,揭示了非饱和膨胀土的“滞后效应”机理。(2)基于不同水力路径下不同含水量时的膨胀土抗剪强度试验结果表明,当土体由饱和状态进入非饱和状态后,所产生的基质吸力会对土体强度的提升产生积极影响。这种强度贡献形式,主要表现为通过转化为土体粘聚力的形式来实现。但不能就此认为膨胀土基质吸力越大或含水量越低,其强度会相应的持续加大。因为在其含水量的正常变动范围内,由于基质吸力贡献作用而存在一个强度峰值。通过对研究区饱和膨胀土样本进行固结试验,掌握了该地区饱和膨胀土在不同加载条件下的固结变形特征,得到了相应的固结变形模型方程,并将膨胀土排水固结变形情况予以程序实现。按照土样采集时所处的应力环境进行加载偏应力路径设置,完成了六级加载条件下的三轴蠕变试验。在试验数据分析的基础上提出了相应的蠕变模型方程。结合固结变形与蠕变变形模型方程,对膨胀土流变特性进行描述。(3)根据汉中地区膨胀土的XRD图谱,确定了其产生胀缩特性的主要亲水性矿物组份和含量,并通过微观结构扫描手段,确定了含水量变化时,土体矿物产生物化反应及土体颗粒排列与接触形式(面-面、点-面以及点-点三种形式)的规律。为了进一步分析非饱和膨胀土裂隙发育特征,基于Otsu理论的图像分割算法编写了裂隙识别程序,提出了可用于描述裂隙率与含水量的经验型函数关系式。(4)利用裂隙均布理论以及本文所得的裂隙率与含水量经验型函数关系式,通过数值模拟手段,对不同裂隙发育状况下的汉中地区膨胀土路堑边坡,进行了雨水入渗时坡体变形发展规律及潜在滑坡形态等方面的研究。较为深入的认识了降雨诱发膨胀土滑坡的机理。在此基础上,综合考虑蒸发进程、降雨持时以及降雨强度等因素的影响,提出了适用于汉中地区降雨诱发滑坡的预警性降雨阈值的经验公式。(5)针对研究区雨水作用下含裂隙膨胀土路堑边坡的工程特性,提出了锚杆框架梁式滑坡防治结构体系,并重点进行了相应的优化设计分析。
[Abstract]:As a kind of special soil properties of expansive soil, with water content changes showed significant swelling, shrinkage, bearing characteristics of large amplitude attenuation after immersion. These are different from other types of engineering geological characteristics of the soil, the slope of the road. Also showing a steady performance in particular. In ten days near the high-speed Shaanxi Mianxian province Hanzhoung Wuhou service area of expansive soil cutting slope as the research object, using laboratory test, theoretical analysis, numerical simulation and calculation procedures for the development of a comprehensive way, in-depth grasp of the basic characteristics of expansive soil in the area, and then carry out the deformation mechanism of expansive soil landslide induced by rainfall considering cracks the influence of rainfall warning threshold and protective measures of expansive soil landslide research work, has made the following aspects of research results and main conclusions: (1). A transient performance cycle test, the expansive soil in Hanzhoung area, different hydraulic path under the condition of soil water characteristic curve (SWCC), and based on the curve data derived permeability coefficient characteristic function of the corresponding curve (HCF). The experimental results show that in the same type of different hydraulic path in the process of expansive soil that will show obvious differences in hydraulic characteristics, which is obviously a "lag effect". Starting from the microscopic structure, explores the pore water storage and seepage, reveals the unsaturated expansive soil "lag effect" mechanism. (2) experimental results show that the strength of expansive soil based on different hydraulic path under different water content when the shear, when the soil is saturated state to unsaturated state, matrix suction generated will have a positive impact on the strength of soil improvement. The strength contribution form, mainly is through the transformation As the soil cohesion form. It can not be considered a more expansive soil matric suction or water content is low, the strength of the corresponding increase. Because in the normal range of moisture content, because the contribution of matrix suction and there is a peak intensity. By analyzing the saturated consolidation test the expansive soil samples, grasp the deformation characteristics of the area of consolidation of saturated expansive soil under different loading conditions, the model equations of deformation corresponding consolidation, and consolidation deformation of expansive soil will be program. According to the soil sampling when the stress environment loading deviatoric stress path set, completed three the triaxial creep test of six loading conditions. Based on the analysis of the test data on the creep model equations. Combining with the consolidation deformation and creep deformation model equation on the rheology properties of expansive soil Described. (3) according to the XRD of expansive soil in Hanzhoung area, the swelling characteristics of major hydrophilic mineral components and content were determined, and the micro structure of scanning method, to determine the change of water content, soil minerals to produce chemical reaction and soil particle arrangement and the contact form (face to face. Point to surface and point point) three forms of law. In order to further analyze the unsaturated expansive soil fissure characteristics, Otsu image segmentation algorithm developed fracture theory recognition program based on the proposed can be used to describe the fracture rate and type of experience type relationship moisture. (4) the use of uniform theory and fracture the fracture rate and water content of experience formula, by means of numerical simulation, expansive soil cutting slope of different crack growth under the condition of the Hanzhoung region, the rain infiltration when the slope deformation regularity and potential slip Study of slope shape. More in-depth understanding of the mechanism of rainfall induced landslide of expansive soil. On this basis, considering the evaporation process, rainfall duration, rainfall intensity and other factors influence, put forward the empirical formula of rainfall warning threshold for Hanzhoung area rainfall induced landslide value. (5) according to the project the characteristics of expansive soil slope with cracks under the effect of rain area, put forward the anchor frame beam structure of landslide prevention system, and analyzes the corresponding optimization design.

【学位授予单位】：西南交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU443;P642.22

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