【作者】 王志华；

【导师】 辛全才；

【作者基本信息】 西北农林科技大学 ， 水利水电工程， 2009， 硕士

【摘要】 在我国西北黄土地区的高含沙河流上,水库建成之后的短短几年内坝前就会淤积一层厚厚的泥沙,在坝前形成天然的防渗铺盖,起到防渗作用。特别是对于中、小型水利工程,当坝基覆盖层深厚,缺乏采用垂直防渗设施的条件或其造价昂贵难以实现时,坝前泥沙淤积不失为一种良好的防渗手段。不但可以起到防渗效果,而且对于中、小型水利工程可以不做地基防渗处理起到降低工程造价的作用。本文以西北黄土地区范沟水库为研究对象,分析了坝前泥沙淤积对其渗流场与应力场的影响,进行了渗流场与应力场的耦合分析,取得的主要研究成果如下:1、阐述了我国西北地区高含沙河流的形成机理、高含沙河流给工程带来的主要问题、水库淤积的横断面形态和水库淤积泥沙粒径的分布。为研究泥沙淤积对中小型水库渗流场与应力场的影响提供了理论依据。2、泥沙淤积对渗流场和边坡稳定的影响分析结果表明:坝前泥沙淤积到一定厚度后,土石坝的浸润线明显下降,同时土石坝的渗漏量明显减小,土石坝上下游边坡随泥沙高度的增加安全系数也逐渐增大,说明对于高含沙河流上的中小型土石坝来说泥沙淤积能起到防渗铺盖的作用,可以利用坝前泥沙淤积做为防渗手段。研究其对应力场的影响分析结果表明,随着泥沙高度的增加,水库在正常水位情况下运行,坝体的位移与应力都有所增加,由于影响比较明显,考虑运用泥沙淤积做为防渗手段时,应该考虑泥沙对应力场的影响。3、探讨了渗流场与应力场的耦合机理,针对应力场对土体孔隙率的影响,渗流场引起应力场的变化进行了量化分析,探讨了考虑应力场变化影响的渗透系数的计算方法,考虑渗流场和应力场的相互作用,得到岩土介质渗流场和应力场耦合的数学模型以及考虑两场耦合作用的有限元计算格式。4、介绍了渗流场与应力场耦合分析在geo-studio软件中实现的步骤。以范沟水库为例进行渗流场与应力场耦合分析,对计算结果进行了分析,表明渗流场与应力场之间的影响比较大,在工程实践中应该考虑渗流场与应力场的耦合作用。更多还原

【Abstract】 In the high-sandiness river of the loess zone in north-west of China,Sediment deposition is formed in front of the dam just a few years after the reservoir built,it formed impervious blanket in front of the dam then play a role in anti-seepage.Especially for small and middle hydraulic engineering,sedimentation in front of the dam is a excellent means of impermeable when the overburden of the dam foundation is too thick so that it lack of facility for the use of vertical anti-seepage conditions or the cost is expensive. It not only have anti-seepage effect but also for small and middle hydraulic engineering cannot make seepage treatment for foundation reducing project cost.Taking the FanGOU reservoir in the loess zone in north-west of China as example,the paper analysised the impact on seepage field and stress field by sedimentation in front of the dam and made couple analysis of seepage field and stress field. The main research result as follow:1、Described the formation mechanism of the high-sandiness river of the loess zone in north-west of China,the main problem caused by high-sandiness river,the reservoir cross-section shape of sedimentation and the distribution of the sedimentation particle size in reservoir.It provide theoretical basis for studying the impact on seepage field and stress field by sedimentation.2、The analysis result of the impact on seepage field by sedimentation show:when the sedimentation is a certain thickness,the saturation line decreased significantly and seepage discharge of the dam reduced obviously.it show sedimentation can play a role in anti-seepage as impervious blanket,we can use sedimentation as anti-seepage mean in small and middle earth-rock dam in high-sandiess river.the analysis result of the impact on stress field by sedmentation show:with the hight of the sedimentation,the displacement and stress of the dam increased when the reservoir operation in normal water level,the impact is significant so we should consider the impact on stress field by sedimentation when we use sedimentation as anti-seepage mean.3、The paper studied couple mechanism of seepage field and stress field,and the influence of the stress field on the soil porosity ratio and the seepage on the stress field are analysed quantificationally.The method to determine the coefficient of permeability considering the varity of stress field is investigated.The mathematical coupling model soil seepage field with stress field and the scheme of FEM calculation considering the effect of two fields’coupling are suggested.4、Introduce the realization step in software GEO-STUDIO of the seepage field and stress field coupling analysis.Taking FanGou reservoir as example,the paper made coupling analysis of seepage field and stress field.The results of the analysis show the impact between seepage field and stress field is relatively great.In engineering pratice we should consider coupling effect of seepage field and stress field.更多还原