基于随机场理论的单裂隙非饱和渗透系数研究

发布时间：2018-04-16 23:35

本文选题：裂隙 + 随机场　；参考：《哈尔滨工业大学》2013年硕士论文

【摘要】：膨胀土在我国二十多个省份都有发现，其中主要分布在河南、广西和湖北等省份。因为膨胀土遇水膨胀失水收缩，因此它极易发育裂隙。裂隙可诱发边坡失稳、基坑坍塌等工程事故。其主要原因是裂隙的存在使得降雨入渗，造成承载力降低。为了给工程设计和地质灾害评估提供良好的依据，对于土体抑或岩体中裂隙的水力特性进行研究是很有必要的。裂隙的非饱和水力特性主要包括持水曲线和渗透系数曲线两部分。本文主要从理论分析和试验量测两个方面对单裂隙饱和-非饱和渗透系数进行了深入的研究，，同时也发展了一种考虑圈闭效应的数值方法。数值方法方面，运用随机场数据生成方法生成服从一定随机场参数的裂隙开度数据，然后利用毛细定律并考虑圈闭效应，得到了随机单裂隙的持水曲线和渗透系数曲线。并将程序得到的持水曲线与相同开度分布参数的单裂隙试验结果进行了对比，对比发现圈闭效应较好的解释了试验得到的持水曲线有较大残余含水量的问题。理论分析方面，建立了裂隙开度的随机场模型；并求解了随机单裂隙饱和-非饱和渗透系数的上限解和下限解；同时研究了裂隙开度分布随机场参数对单裂隙渗透系数的影响。研究发现单裂隙饱和渗透系数在两种极限工况条件下都受裂隙开度均值的影响最大；两种工况条件下渗透系数开始出现下降时对应的基质吸力都取决于裂隙所能取得的最大开度值；裂隙离散尺寸越大，渗透系数下降段的斜率越大。试验仪器方面，研制了进气值较高、渗透系数较大的新型毛细栅栏。该毛细栅栏的饱和渗透系数为1.80×10-3m/s，进气值为0.55kPa。利用新型毛细栅栏对稳态非饱和渗流试验装置进行改进，从而测量得到了单裂隙的非饱和渗透系数。发现单裂隙的非饱和渗透系数随着基质吸力的改变分为三个阶段变化：平稳段、急剧下降段和缓慢下降至零段。通过对试验结果和理论分析的对比，发现理论分析结果能够很好反映试验中裂隙渗透系数的变化趋势和范围；通过试验结果与数值结果的对比发现这两种方法的结果基本吻合。
[Abstract]:Expansive soil has been found in more than 20 provinces of China, mainly in Henan, Guangxi and Hubei provinces.Because expansive soil shrinks when water expands and loses water, it is easy to develop fissures.Cracks can induce slope instability, foundation pit collapse and other engineering accidents.The main reason is that the existence of cracks causes rainfall infiltration, resulting in the reduction of bearing capacity.In order to provide a good basis for engineering design and geological hazard assessment, it is necessary to study the hydraulic characteristics of fractures in soil or rock mass.The unsaturated hydraulic characteristics of fractures mainly include water retention curve and permeability coefficient curve.In this paper, the saturation-unsaturated permeability coefficient of a single fracture is studied from two aspects: theoretical analysis and experimental measurement. At the same time, a numerical method is developed to consider the trap effect.In terms of numerical method, the random field data generation method is used to generate crack opening data from certain random field parameters, and then the water holdup curve and permeability coefficient curve of random single fracture are obtained by using the law of capillary and considering the trap effect.The results of single fracture test with the same opening distribution parameters are compared with the results obtained by the program. It is found that the trap effect can explain the problem that there is a large residual water content in the water retention curve obtained by the test.In theoretical analysis, the random field model of fracture opening is established, the upper and lower bound solutions of random single fracture saturation-unsaturated permeability coefficient are solved, and the influence of random field parameters of fracture opening distribution on single fracture permeability coefficient is studied.It is found that the saturation permeability coefficient of single fracture is most affected by the mean of crack opening under two kinds of limit working conditions.When the permeability coefficient begins to decrease, the matrix suction depends on the maximum opening value obtained by the fracture, and the larger the size of the fracture is, the bigger the slope of the descending section of the permeability coefficient is.A new type of capillary fence with high air intake value and high permeability coefficient has been developed.The saturation permeability coefficient of the capillary fence is 1.80 脳 10 ~ (-3) m / s and the air intake value is 0.55 KPA.A new type of capillary fence is used to improve the steady unsaturated seepage test device, and the unsaturated permeability coefficient of a single fracture is obtained.It is found that the unsaturated permeability coefficient of a single fracture can be divided into three stages with the change of the matrix suction: steady phase, sharp descent stage and slow down to zero stage.By comparing the experimental results with the theoretical analysis, it is found that the theoretical analysis results can well reflect the variation trend and range of the fracture permeability coefficient in the test, and the comparison between the experimental results and the numerical results shows that the results of the two methods are basically consistent.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU43;TU443

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