【作者】 林涛；

【导师】 钱会；

【作者基本信息】 长安大学 ， 水文学及水资源， 2018， 硕士

【摘要】 本文依托国家自然科学基金项目“重塑黄土渗透性变化规律及其机制研究”,以陕西省泾阳县南塬修石渡剖面黄土为研究对象,在对剖面逐米取样的基础上利用Mastersize-2000型激光粒度仪和GUANTA-200型环境扫描电子显微镜等仪器,对修石渡剖面黄土的粒度组成、微观结构特征以及物理性质指标进行了系统研究。结合该剖面黄土颗粒粒度的分布规律和室内土工试验测得的基本物理性质指标,对该剖面黄土的结构特征及孔隙分布进行了深入分析,获得了剖面微观结构随埋深变化的规律。主要研究成果归纳如下:（1）对修石渡剖面黄土颗粒组成进行了分析,得出剖面黄土的颗粒组成主要以粗粉砂为主,黏粒次之,其中黄土层的粗粉砂含量大于53.32%,而古土壤层的粗粉砂含量在45.25%;古土壤层中黏粒含量高于黄土层,且黏粒含量有随深度增加的趋势。（2）通过分析整个剖面土体的微观结构图像,对骨架颗粒的组成单元体、接触方式、以及胶结类型进行了描述与分析,总结了黄土的微观结构特征随埋深的变化规律,认为骨架颗粒的接触方式、胶结类型及其组成的单元体是决定黄土孔隙类型的主要因素;剖面土体的骨架颗粒单元体由粗碎屑物和集粒以不同赋存比例共同组成,其中在L₁和L₂层黄土骨架颗粒单元体仅由粗碎屑物单独组成,其他地层均以二者共同存在的形式组成了黄土骨架颗粒单元体。（3）修石渡剖面土体结构类型变化、波动幅度整体随埋深的增加而逐渐变小,离石黄土的结构类型随埋深的波动变化均比坡头黄土和马兰黄土小,但在黄土-古土壤接触带的土体结构类型差异大,波动性较大。（4）利用IPP6.0图像处理软件反复统计计算,将得到的孔隙面积比与孔隙率进行对比验证,最终确定微观结构定量分析过程中图像的最佳放大倍数为800X、阈值为灰度分布曲线峰值的左侧一格;根据孔隙面积比是孔隙二维截面的特征,将孔隙面积比作为微观结构研究中的主要评价指标,并利用线性方程对剖面土体水平面和垂直面的孔隙面积比与深度进行拟合,发现两者存在线性关系且孔隙面积比随埋深增加呈减小趋势,垂直面上的孔隙面积比曲线随深度的变化更具有规律性。（5）剖面土体在水平面和垂直面中的孔隙主要以微孔隙和小孔隙为主,其中黄土中微孔隙的含量小于古土壤,随着埋深增加微孔隙含量显著增大,大、中、小孔隙含量均减少。（6）通过对孔隙的分型维数进行分析,得出土体的孔隙分布密度随着深度逐渐变小,集团化程度逐渐降低,分布越分散,孔隙越复杂。更多还原

【Abstract】 This paper relies on the project of national natural science foundation of China"reconstructing the law and mechanism of loess permeability change",taking the loess section of the south Jingyang Plateau in ShaanXi province（Xiushiduadu Village）as the research object,this paper started with the research methods of macroscopic mechanics and microstructure.By usingMastersize-2000 laser particle size analyzer and GUANTA-200Environmental Scanning Electron Microscope and other instruments,systematic study of the grain size composition,microstructure characteristics and physical properties of loess in Xiushidu section.Combined with the distribution law of loess granularity and the basic physical properties measured by laboratory geotechnical tests,the structural characteristics and pore distribution of the loess were analyzed in detail,and the law of the microstructure change with depth was obtainedThe main conclusions are as follows:（1）According the results of particle size analysis of loess particles,the composition of loess is mainly composed of coarse silt,followed by clay,in which the coarse silt content in loess layer was 53.23%,while the coarse silt content in paleosol layer was 45.25%,the content of clay in ancient soil layer is more than loess layer,and the clay content increases with depth.the microstructure of the soil was observed and photographed by ESEM,and the skeleton shape,structure type,cementation form and pore characteristics of the soil were described.（2）By analyzing the microstructure images of the whole section loess,the description and analysis of the basic unit element,contact mode,and cementation type of the skeleton particles were analyzed.The variation of microstructure characteristics of loess with depth were summarized.The basic unit element in loess microstructuren composite can be sumed up as granular unit and aggregated unit,other strata were composed of loess matrix particles in the form of their common existence,only L₁ and L₂ layers of loess skeleton particles are composed of coarse clastic elements.（3）The fluctuation amplitude of the type of soil structurewith the increase of the buried depth in the section decreases gradually,the structural type of the soil from thelishi loess was less fluctuating than the Malan loess.Moreover,the soil structure types of the loess-paleosoil contact zone are large and volatile.（4）The pore area ratio by using IPP6.0 image processing software and porosity were verified.Finally,the optimal magnification and threshold value of the microstructure image were determined respectively as the 800X andthe first number of the peak value of grayscale distribution curve respectively.According to the pore area ratio as a feature of the two-dimensional cross-section of the pore,the ratio of the pore area is taken as the main evaluation parameter in the microstructural study process.The pore area ratio of horizontal plane and vertical plane of soil sample is fitted with linear equation,the pore area ratio decreased with the increase of buried depth.（5）The horizontal plane and vertical plane of the loess were mainly micro-pores and small pores,In loess strata in the content of micro pore less than ancient micropore content in soil formation,with the increase of loess sample depth,the pore size and pore size decreased with the increase of buried depth.（6）By analyzing the fractal dimensions of the pores,the pore distribution of the soil tends to disperse with increasing depth.The lower the degree of collectivization,the smaller the distribution density and the more complicated the pores.更多还原