基于CT扫描对植被发育斜坡土体大孔隙和渗透性的研究

发布时间：2018-03-12 06:49

本文选题：植被发育斜坡　切入点：滑坡　出处：《昆明理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：山区流域植被发育斜坡的失稳往往尾随强降雨发生,降雨入渗引起的地下水位上升是导致斜坡失稳的主要原因,而饱和渗透系数是评价土体的渗透特性的主要参数,大孔隙分布规律及其结构特征是影响土体渗透性的关键因素,因此对植被发育斜坡土体大孔隙和渗透性展开研究是很有必要的。本文以头寨沟植被发育斜坡土体为研究对象,采用现场调查、现场试验、室内试验和送样分析等手段对植被发育斜坡区域地质特征、气候特征和土体的物理性质等进行全面分析；利用CT扫描技术和图像处理技术获得该区土体大孔隙尺寸分布规律和形状特征；利用环刀法测定土体饱和渗透系数,并与毛细管束模型预测的饱和渗透系数进行对比研究。具体的工作和得到的结论如下：(1)对试验点植被发育斜坡区域地质调查、气象监测和土体物理性质等进行分析。得到结论：头寨沟滑源区较坡脚降雨量偏大,而气温偏低；试验点土体天然密度、干密度和比重较草本植被区土体偏小,天然含水率和孔隙比却偏大；试验点土体有机质含量比农业土壤高6-10倍,土体中根系主要分布于表层50cm范围内,微生物类型以细菌为主,微生物总量随深度有递减的趋势；试验点土体粘粒的矿物成分主要是石英、蒙脱石和斜长石等,个别样品还含有少量高岭石。(2)运用CT扫描技术获得土体大孔隙分布特征和形状特征。得到结论：CT扫描技术用于分析土体大孔隙精度较高；大孔隙度随深度增加有减小的趋势,各孔径级别的大孔隙数量随孔径级别增加呈指数规律递减；随深度增加土体大孔隙形状越狭长；大孔隙等效直径越大其轮廓越粗糙。(3)优先流的观察,饱和渗透系数的测定以及与预测结果的对比分析。得到结论：优先流的主要通道为动物洞穴、根土间隙、干缩裂缝和腐烂根系通道等大孔隙；环刀法测定的饱和渗透系数随深度增加呈递减的趋势；根据毛细管束模型预测所得的饱和渗透系数与实测值存在一定偏差,但两者在同一数量级内；修正后的毛细管束模型预测值精度明显提高,修正后的预测值与实测值的均方根误差由0.64减小到0.41。
[Abstract]:The instability of vegetation development slopes in mountainous areas is often followed by heavy rainfall. The rise of groundwater level caused by rainfall infiltration is the main cause of slope instability, and the saturation permeability coefficient is the main parameter to evaluate the permeability characteristics of soil. The distribution law of macropores and its structural characteristics are the key factors affecting soil permeability. Therefore, it is necessary to study the macroporosity and permeability of soil on the slope of vegetation development. This paper takes the soil mass of Touzhaigou vegetation development slope as the research object. By means of field investigation, field test, laboratory test and sample delivery analysis, the geological characteristics, climate characteristics and physical properties of soil in the slope region of vegetation development are comprehensively analyzed. By using CT scanning technique and image processing technique, the size distribution and shape characteristics of macroporous soil in this area are obtained, and the saturated permeability coefficient of soil is measured by using the annular knife method. And compared with the saturated permeability coefficient predicted by the capillary beam model. The concrete work and the conclusion obtained are as follows: 1) the regional geological survey of the vegetation development slope in the experimental site. The results of meteorological monitoring and physical properties of soil are as follows: the rainfall in Touzhaigou sliding source area is higher than that in the foot of slope, but the temperature is lower, and the natural density, dry density and specific gravity of soil in the test site are smaller than that in herbaceous vegetation area. The content of organic matter in the soil is 6-10 times higher than that in the agricultural soil, the root system of the soil is mainly distributed in the surface layer of 50cm, the microorganism type is mainly bacteria, and the total amount of microorganism is decreasing with the depth of the soil, and the content of organic matter in the soil is 6-10 times higher than that of the agricultural soil. The mineral composition of clay in the soil of the test site is mainly quartz, montmorillonite and plagioclase, etc. Some samples also contain a small amount of kaolinite. 2) the distribution and shape characteristics of macropores in soil are obtained by CT scanning technique. It is concluded that the accuracy of macroporosity analysis is high, and the macroporosity tends to decrease with the increase of soil depth. The number of macropores at each pore size level decreases exponentially with the increase of pore size level; with the increase of depth, the shape of macropore is longer and narrower; the larger the equivalent diameter of macropore is, the rougher the contour is. It is concluded that the main channels of preferential flow are animal caves, root soil gaps, dry shrinkage cracks and rotting root channels. The saturation permeability coefficient measured by the annular knife method is decreasing with the increase of the depth, the saturation permeability coefficient predicted by the capillary bundle model has a certain deviation from the measured value, but both of them are in the same order of magnitude. The precision of the modified capillary bundle model is improved obviously, and the root mean square error between the predicted value and the measured value is reduced from 0.64 to 0.41.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P642.2

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