坡表碎石土质量密度及渗透特性的空间变异性研究

发布时间：2018-04-30 14:40

本文选题：碎石土 + CT技术　；参考：《湘潭大学》2015年硕士论文

【摘要】：堆积碎石土作为一种常见的地质体在我国中南及西北地区广泛分布,往往因降雨侵蚀或工程活动诱发地质灾害(如滑坡和泥石流等)给我国带来巨大的经济损失和人员伤亡。然而,因碎石土的物质组成复杂及其不规则的结构分布,给其工程性质与细观结构的研究带来了极大的困难。本文以湖南昭山地区某堆积碎石土斜坡为研究坡体,基于图像处理技术和室内试验研究坡表碎石土质量密度的空间变异特性,采用高倍光学显微镜观察碎石土中细小黏粒的细观孔隙特征,基于Darcy定理对碎石土进行室内饱和渗透试验,并采用CT层析技术获取碎石土试样的孔隙特征,试图探讨碎石土的孔隙特征与其渗透系数的相关性,进而加深我们对这种复杂岩土材料的了解,为今后碎石土降雨滑坡类似工程问题提供参考。主要研究成果如下:1.研究坡体碎石土的含石量在49.75%~77.63%之间,沿坡面向下降低,其中0~10mm粒径区间的颗粒含量沿坡面向下显著增加,20~60mm粒径区间的颗粒含量沿坡面向下呈减小趋势,而10~20mm粒径区间内变化不明显;圆度频率主要分布在0.7~0.9区间内,累计频率的平均值为77.3%;块体长短轴比的平均值位于1.4~1.497之间,且沿坡面向下有变小趋势;碎石复杂度沿坡面向下有增加趋势。2.试验表明,相同质量细小黏粒土体的孔隙度与含水率之间呈二次曲线相关;孔隙数目、孔隙复杂度以及孔隙变异度随着含水率的增加而减小,表明含水率越小孔隙的扭曲程度越高,孔隙就越复杂,且孔隙数含量越多,越有利于表层雨水下渗。3.正交试验结果分析表明,对碎石土孔隙特征及其渗透系数影响的主次顺序为:含石量干密度级配类型;碎石土的孔隙度、孔隙数目和渗透系数随含石量增加而增加,而孔隙变异度和孔隙复杂度随含石量的增加而减小;结合碎石土的孔隙特征分析,发现碎石土的渗透系数与其孔隙特征值之间存在指数递减关系。
[Abstract]:As a common geological body, the accumulative gravel soil is widely distributed in the central, southern and northwest regions of China. It often brings huge economic losses and casualties to our country because of rainfall erosion or engineering activities induced geological disasters (such as landslides and debris flows). However, because of its complex composition and irregular structural distribution, it is very difficult to study its engineering properties and mesostructures. Based on image processing technique and laboratory test, the spatial variation characteristics of mass density of gravel soil on slope surface are studied in this paper, which is based on the slope of a pile of gravel in Zhaoshan area, Hunan Province. High power optical microscope was used to observe the microscopic pore characteristics of fine clay in gravel soil. The laboratory saturated permeability test was carried out on the basis of Darcy's theorem, and the pore characteristics of gravel soil sample were obtained by CT tomography. This paper attempts to discuss the correlation between pore characteristics and permeability coefficient of gravel soil, and then to deepen our understanding of this complex rock and soil material, and to provide reference for similar engineering problems of rainfall landslide of gravel soil in the future. The main research results are as follows: 1. The content of stone in the gravel soil of slope body is between 49.75% and 77.63%, and the content of particles in the 0~10mm particle size range increases significantly along the slope surface, and the particle content of the grain size range of 200.60 mm decreases along the slope surface. But the variation of 10~20mm particle size range is not obvious, the roundness frequency is mainly distributed in 0.7 ~ 0.9 region, the average value of cumulative frequency is 77.3%, the average value of the long and long axis ratio of block is between 1.4 and 1.497, and there is a tendency to decrease along the slope. The gravel complexity increased along the slope. 2. 2. The results show that the porosity of fine clay soil of the same mass is conic with water content, and the number of pores, the complexity of pores and the variation of porosity decrease with the increase of water content. The smaller the water content is, the higher the distortion degree of pore is, the more complex the pore is, and the more the content of pore number is, the more favorable to surface Rain Water's infiltration. 3. The results of orthogonal test show that the primary and secondary order of influence on pore characteristics and permeability coefficient of gravel soil is as follows: dry density gradation type of rock content, porosity, number of pores and permeability coefficient of gravel soil increase with the increase of stone content. The porosity variation and pore complexity decrease with the increase of stone content, and the relationship between permeability coefficient and pore characteristic value is found to be exponentially decreasing according to the analysis of pore characteristics of gravel soil.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU43

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