渐进展开理论在土中渗流及物质运移中的研究
发布时间：2018-07-16 14:54
【摘要】：岩土介质是自然界中广泛存在的非均匀多孔介质。固态颗粒的不同形状大小、孔隙的空间排布形式以及土体内部复杂组分等因素构成了岩土介质典型的非均质特性。与其相关的渗流以及物质运移现象是岩土工程领域研究的基础课题之一。目前主要研究手段是从宏观体入手,采用唯象方法。但宏观单元表现出的性质本质上是微观尺度物理化学现象的反映。以该思路出发,应从微观角度充分考虑孔隙特征,并将孔隙内发生的各种物理化学过程与宏观体的渗流以及物质运移联系起来。这样将更为本质地对这一课题进行研究。 基于以上考虑,本文借助双尺度渐进展开方法,针对多孔介质基本物理量弯曲度、土体内渗流现象以及物质运移现象,开展了从微观到宏观的理论展开分析及数值计算工作,并得到下列成果： (1)分别采用几何路线方法和双尺度渐进展开方法,针对圆形颗粒及方形颗粒多孔介质,建立了相应的弯曲度-孔隙率模型关系。提出多孔介质弯曲度与孔隙率的自然对数成线性关系。不同介质弯曲度模型间的差异主要体现在自然对数前的特征系数。针对不同颗粒形状的多孔介质,计算得出了特征系数的下限值。所求模型与玻璃颗粒的多孔介质实测值对比,发现有着较好的吻合程度,验证了本文方法的合理性。对于自然土体,通过实际情况分析了物理吸附(吸湿水)、化学吸附以及颗粒排列三个对土体弯曲度影响比较大的因素并进行了计算,得到了土体中弯曲度的影响因素,并定量得到了不同影响因素下的模型。 (2)基于Navier-Stokes方程,得到多孔介质渗透率的双尺度计算解答。计算结果显示,对于渗透率的计算,排列形式几乎没有影响,而颗粒形状、颗粒大小以及孔隙率却存在着较为显著的影响,颗粒大小、孔隙率与渗透率之间是正相关的。同时将该解答应用于砂土、高岭土、伊利土以及海洋粘土渗透率预测计算中。 (3)通过对弥散方程的尺度扩展,得到了强扩散模型、弱扩散模型、弥散模型、均质化不适用四种模型以及不同模型间的界限阈值。同时得到有效扩散系数的双尺度计算解答。计算显示,对于有效扩散系数的计算,颗粒大小以及排列形式几乎没有影响,而颗粒形状与孔隙率却存在着较为显著的影响。另一方面,可将该解答应用于土体的有效扩散系数预测计算中。与渗透率的双尺度解答对比发现,在渗流与扩散的参量影响因素中,相同的是孔隙率对于渗透率及有效扩散系数的影响都为正向的,颗粒排列都没有影响,所不同的是,颗粒大小对渗透率的结果有影响,而与有效扩散系数最终值无关。 (4)弯曲度随孔隙率的变化而变化,但现有的一些渗流模型中将弯曲度视为一定值,这种处理方式是有失妥当的。通过本文建立的弯曲度-孔隙率关系式,对Bruschke and Advani理论模型进行了修正,修正后的模型与修正前相比,与渗透率双尺度计算解有着更为良好的吻合程度。 (5)通过对有效扩散系数与弯曲度间关系的理论推导以及本文建立的弯曲度-孔隙率模型,提出了有效扩散系数与分子扩散系数比值的上限。该上限值存在的本质原因是不同形状颗粒的弯曲度存在着最小值。所得模型能较好的包含非饱和土体中的相关实测数据。
[Abstract]:Geotechnical medium is a widely distributed heterogeneous porous medium in nature. The different shapes and sizes of solid particles, the spatial arrangement of pores, and the complex components in the soil form the typical heterogeneity of the rock and soil medium. The related seepage and material migration are the basic subjects in the field of geotechnical engineering. At present, the main research means is to start with macroscopic bodies and adopt phenomenological methods. However, the nature of the macro unit is essentially a reflection of the microscopic physical and chemical phenomena. In this way, the pore characteristics should be fully considered from the microscopic point of view, and the various physical and chemical processes occurring in the pores and the percolation and objects of the macroscopic bodies should be taken into consideration. Qualitative migration is linked, so that this subject will be studied in a more essential way.
Based on the above considerations, with the help of the two scale progressive expansion method, the theoretical analysis and numerical calculation are carried out from microcosmic to macroscopic, and the following results are obtained in view of the basic physical quantity bending of porous media, the phenomenon of seepage in the soil and the phenomenon of material migration.
(1) the relationship between the bending degree and porosity model of the circular particles and the square particle porous media is established by using the geometric route method and the double scale progressive expansion method. The linear relationship between the natural logarithm of the porosity and the porosity of the porous medium is put forward. The difference between the bending models of different medium is mainly reflected before the natural logarithm. The lower limit of the characteristic coefficient is calculated for porous media with different particle shapes. The model is compared with the measured value of the porous media of the glass particles. It is found that there is a good degree of anastomosis and the rationality of the method is verified. Physical adsorption (hygroscopic water) and chemistry are analyzed for natural soil. Three factors which have large influence on the soil bending degree are calculated by adsorption and particle arrangement, and the influence factors of the bending degree are obtained, and the models under different influence factors are obtained.
(2) a double scale solution of porous medium permeability is obtained based on the Navier-Stokes equation. The calculation results show that there is little influence on the arrangement form for the calculation of permeability, but the particle size, particle size and porosity have a more significant influence. The particle size, porosity and permeability are positively correlated. The solution is applied to the prediction of sand, kaolin, illite and marine clay permeability.
(3) by extending the dispersion equation, the strong diffusion model, the weak diffusion model, the dispersion model, the homogenization of the four models and the threshold values between different models are not applied. The effective diffusion coefficient is obtained by the double scale calculation solution. The calculation shows that the size and arrangement of the effective diffusion coefficients are almost the size and the arrangement form. On the other hand, the solution can be applied to the prediction of effective diffusion coefficient of soil. In comparison with the double resolution of permeability, it is found that the same is the porosity for permeability and effective diffusion coefficient in the factors affecting the permeability and diffusion parameters. All the effects are positive. The particle size has no effect on the particle size, and the size of the particles has an effect on the results of the permeability, but it has nothing to do with the final value of the effective diffusion coefficient.
(4) the bending degree varies with the change of porosity, but in some existing seepage models, the bending degree is considered as a certain value. This method is inappropriate. The Bruschke and Advani theoretical model is corrected by the formula of the curvature porosity and porosity established in this paper. The modified model is compared with the correction before the correction, and the double scale of the permeability is compared with the permeability. The calculated solution has a better degree of anastomosis.
(5) through the theoretical deduction of the relationship between the effective diffusion coefficient and the bending degree and the model of the curvature porosity established in this paper, the upper limit of the ratio of the effective diffusion coefficient to the molecular diffusion coefficient is put forward. The essential reason for the existence of the upper limit is that the bending degree of different shapes of particles has the minimum value. And the relevant measured data in the soil.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU43;O357.3
本文编号：2126735
[Abstract]:Geotechnical medium is a widely distributed heterogeneous porous medium in nature. The different shapes and sizes of solid particles, the spatial arrangement of pores, and the complex components in the soil form the typical heterogeneity of the rock and soil medium. The related seepage and material migration are the basic subjects in the field of geotechnical engineering. At present, the main research means is to start with macroscopic bodies and adopt phenomenological methods. However, the nature of the macro unit is essentially a reflection of the microscopic physical and chemical phenomena. In this way, the pore characteristics should be fully considered from the microscopic point of view, and the various physical and chemical processes occurring in the pores and the percolation and objects of the macroscopic bodies should be taken into consideration. Qualitative migration is linked, so that this subject will be studied in a more essential way.
Based on the above considerations, with the help of the two scale progressive expansion method, the theoretical analysis and numerical calculation are carried out from microcosmic to macroscopic, and the following results are obtained in view of the basic physical quantity bending of porous media, the phenomenon of seepage in the soil and the phenomenon of material migration.
(1) the relationship between the bending degree and porosity model of the circular particles and the square particle porous media is established by using the geometric route method and the double scale progressive expansion method. The linear relationship between the natural logarithm of the porosity and the porosity of the porous medium is put forward. The difference between the bending models of different medium is mainly reflected before the natural logarithm. The lower limit of the characteristic coefficient is calculated for porous media with different particle shapes. The model is compared with the measured value of the porous media of the glass particles. It is found that there is a good degree of anastomosis and the rationality of the method is verified. Physical adsorption (hygroscopic water) and chemistry are analyzed for natural soil. Three factors which have large influence on the soil bending degree are calculated by adsorption and particle arrangement, and the influence factors of the bending degree are obtained, and the models under different influence factors are obtained.
(2) a double scale solution of porous medium permeability is obtained based on the Navier-Stokes equation. The calculation results show that there is little influence on the arrangement form for the calculation of permeability, but the particle size, particle size and porosity have a more significant influence. The particle size, porosity and permeability are positively correlated. The solution is applied to the prediction of sand, kaolin, illite and marine clay permeability.
(3) by extending the dispersion equation, the strong diffusion model, the weak diffusion model, the dispersion model, the homogenization of the four models and the threshold values between different models are not applied. The effective diffusion coefficient is obtained by the double scale calculation solution. The calculation shows that the size and arrangement of the effective diffusion coefficients are almost the size and the arrangement form. On the other hand, the solution can be applied to the prediction of effective diffusion coefficient of soil. In comparison with the double resolution of permeability, it is found that the same is the porosity for permeability and effective diffusion coefficient in the factors affecting the permeability and diffusion parameters. All the effects are positive. The particle size has no effect on the particle size, and the size of the particles has an effect on the results of the permeability, but it has nothing to do with the final value of the effective diffusion coefficient.
(4) the bending degree varies with the change of porosity, but in some existing seepage models, the bending degree is considered as a certain value. This method is inappropriate. The Bruschke and Advani theoretical model is corrected by the formula of the curvature porosity and porosity established in this paper. The modified model is compared with the correction before the correction, and the double scale of the permeability is compared with the permeability. The calculated solution has a better degree of anastomosis.
(5) through the theoretical deduction of the relationship between the effective diffusion coefficient and the bending degree and the model of the curvature porosity established in this paper, the upper limit of the ratio of the effective diffusion coefficient to the molecular diffusion coefficient is put forward. The essential reason for the existence of the upper limit is that the bending degree of different shapes of particles has the minimum value. And the relevant measured data in the soil.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU43;O357.3
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