【作者】 任权；

【导师】 王家鼎；

【作者基本信息】 西北大学 ， 地质工程， 2008， 硕士

【摘要】 黄土具有孔隙大、松散、遇水易变形的特点,公(铁)路沿线的黄土滑坡、振(震)陷等地质灾害频繁发生,危害严重,极大地阻碍了交通事业的快速发展,并对黄土地区的经济建设和社会发展造成巨大的影响。为此本文在总结国内外有关黄土微观结构、滑带土、土动力学的研究现状的基础上,以黄土地区公(铁)路沿线滑坡为研究对象,结合室内试验,利用定性及定量、半定量分析方法,对列车“长持时、小振幅”振动引起黄土滑坡滑带土微结构的变化进行了较为深入的研究,取得了一些较有价值的研究成果。首先,在对黄土滑坡分布“群体性”特点概括总结的基础上,笔者提出一种新的群体组合类型:公(铁)路沿线型,由此引出本文的主要研究内容,即:列车振动引起黄土滑坡滑带土微观结构变化;其次,笔者在现场勘察的基础上采集大量滑带土样品,并将长持时的正弦荷载通过动三轴仪施加在样品上,研究了滑带土在这种荷载之下的动力特征,结果表明,滑带黄土在一定的固结应力下固结稳定后,不同动应力条件下产生的累积残余应变、动抗剪强度随着振次、固结应力、动应力的变化呈现一定的规律性变化,且滑带黄土仅在较大主应力比条件下表现出振陷性;此外,为研究滑带土体在动荷载作用下的微观结构变化,对试验前后土样进行扫描电镜试验,从扫描电镜照片可以看出原状滑带黄土结构疏松,孔隙形状不规则,完好的单个集粒比较少见,集粒之间相互凝结成块,接触关系多为支架接触,接触模式主要为棱角—棱边接触,滑带黄土经振陷试验后,其结构明显变得密实,孔隙破碎严重且表现出一定的定向性,镜下可见大孔隙明显减少,颗粒接触关系主要为镶嵌接触,接触模式为棱边—棱边接触;最后,利用分形理论,GIS软件等对黄土微结构变化进行定量分析,结果表明,滑带土孔隙微观结构具有一定的分形特征,且各种孔隙微观结构参数随着动应力、主应力比的变化呈现规律性变化,并在此基础上,建立滑带土体微观机构参数同宏观力学性质的线性相关关系。更多还原

【Abstract】 Due to the characteristics of the loess own structure, physical and mechanical properties, the loess landslides, seismic subsidence, dynamic loess settlement and other geological disasters along the highway and railway road occurred frequently and caused seriously endangering, they greatly hinder the rapid development of transport and then bring tremendous impact on the loess region’s economic construction and social development.Based on the present research situation about micro-structure of loess, loess landslide slide-zone soil and soil dynamics at home and abroad, taking the loess landslide along the highway and railway as research subject, combined with laboratory tests, using qualitative and quantitative or semi-quantitative analysis method, the research on the micro-structure change of the slide-zone soil in loess landslide caused by train-induced "minor amplitude and long-term" vibration are carried out. The research work has accomplished with the following achievements.Firstly, on the basis of "group" feature of loess landslides in distribution, a new type of combination of the groups: Loess Landslide along the Highway or Railway, which leads to the main content of this paper, namely: train-induced vibrations caused micro-structural changes of Loess landslide slide-zone soil; Secondly, by imposing long time-sustained sinusoid loading on natural loess specimens which collected on Typical highway Landslide in dynamic triaxial test, characteristic of loess residual strain(dynamic subsidence) has been studied. The result shows that under different dynamic stress conditions, different samples’ cumulate residual strain, dynamic shear strength exhibited regularly changes in the pattern of the change of vibratory times, consolidation stress and dynamic stress, also have their own peculiarity. And the slide-zone soil shows its vibration deformation behaviors only under greater main stress ratio;In addition, there are some scanning electron microscopy (SEM) test on these samples after dynamic triaxial test have been done. The SEM photo shows that undisturbed slide-zone loess have loose structure, irregular pore shape and lesser complete aggregate grain, and these grain intercoagulated and been massive shape, The contact relationship among the soil framework grain are mainly bracket contact, contact mode are mainly corner to edge contact; But after the dynamic triaxial test ,the structure of the samples become more compact and stable, loess pore break up and show the characteristic of orientation, and the quantity of soil macropore decreased significantly, and the contact relationship are mainly mosaic contact, contact mode are mainly edge to edge contact; Finally, Based on the Fractal theory and image-processing techniques such as Photoshop、Arcview、ArcMap, this paper researched the change of pore microstructure of loess under this type of dynamic load, the result shows that the pore microstructure of loess have the character of fractal, and the relation between microstructure parameter of loess sample and the load under different load condition have been studied, the research indicated that these parameters shows regular change along with the dynamic stress, main stress ratio, at last the linear relationship between these parameters and macro-mechanical properties of the slide-zone soil was founded due to the above result.更多还原