细颗粒泥沙静水沉降实验研究

发布时间：2018-02-11 08:57

本文关键词： 细颗粒泥沙絮凝絮体形态密度沉速　出处：《西北农林科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：研究细颗粒粘性泥沙絮凝形成-发育的机理和沉降-淤积运动规律是泥沙运动力学的一个重要课题;对于深入认识水库泥沙淤积、海岸滩涂演变及港口航道维护具有重要意义。目前,很多学者从理论和实践两方面对细颗粒泥沙絮凝沉降进行了研究,但仍有很多问题尚未解决。本文以渭河杨凌河段洪水淤积体为沙洋,运用Ipp图像处理软件、借助分形理论,对絮凝体显微镜图片进行了分析研究,简化了传统计算絮凝体有效密度的计算方法。采用二维数字图像计盒维数的计算方法,运用MATLAB软件,计算了絮凝体的分形维数。从微观方面探讨了絮凝体的有效密度、孔隙率、直径、分形维数在不同含沙量、电解质条件下的变化规律。从宏观方面对细颗粒粘性泥沙絮凝沉降过程进行了试验研究。考虑到天然水体中多含有阳离子,且阳离子对细颗粒泥沙絮凝沉降影响较大,为此,以冈恰洛夫公式为基础,引入离子浓度参数,拟合了絮凝体沉速公式。得出如下结论:(1)在含沙量较小(50g?L、70g?L)时,絮凝体有效密度随着时间呈现出先增大再减小的趋势;当含沙量为(100g?L、150g?L)时,絮凝体有效密度随着时间变化表现为先减小再增大的趋势。(2)在其它影响因素不变条件下,随着电解质强度的增大,絮凝体分形维数呈现出先增加后减小的趋势。(3)絮凝体沉降过程可划分为絮团沉降和絮网沉降两个阶段。并且,在同一电解质条件下,随着含沙量的增大,絮凝体沉降速度逐渐减小并趋于稳定。(4)阳离子化合价对絮凝体沉降速度的影响远大于电解质强度的影响。(5)泥沙粒径对絮体沉降的影响与泥沙浓度、电解质条件密切相关。(6)本文拟合的絮凝体沉速公式与实测计算值更加符合。
[Abstract]:It is an important subject of sediment movement mechanics to study the mechanism of formation and development of fine granular viscous sediment flocculation and the law of sedimentation and silt movement. The evolution of coastal beach and the maintenance of port channel are of great significance. At present, many scholars have studied the flocculation settlement of fine sediment in theory and practice. However, there are still many problems to be solved. In this paper, using the flood silt in Yang Ling reach of the Weihe River as the sand ocean, using the Ipp image processing software, with the help of fractal theory, the microscopic images of flocculants are analyzed and studied. The traditional method of calculating the effective density of flocculant is simplified. The fractal dimension of flocculant is calculated by using MATLAB software and the calculation method of two-dimensional digital image box-counting dimension. The effective density and porosity of flocculant are discussed from the microscopic point of view. The variation law of diameter and fractal dimension under different sediment content and electrolyte condition. The flocculation and settling process of fine granular viscous sediment in macroscopical aspect has been studied. Considering that there are many cations in natural water body, The effect of cations on the flocculation settlement of fine sediment is great. Therefore, based on the Gangcharov formula and introducing the ion concentration parameters, the settling velocity formula of the flocculation is fitted. The conclusion is as follows: 1) the sediment content is less than 50 g? L,70g? When L), the effective density of flocculants increased first and then decreased with time, and when the sediment content was 100g? L,150g? When L), the effective density of flocculants varies with time, which decreases first and then increases. (2) under the condition of constant other influencing factors, with the increase of electrolyte strength, The fractal dimension of flocculants shows a tendency of increasing first and then decreasing. The flocculation settling process can be divided into two stages: flocculation settling and flocculation net settling. Moreover, under the same electrolyte condition, with the increase of sediment content, the flocculation settling process can be divided into two stages. The effect of cationic valence on the settling velocity of flocculant is much greater than that of electrolyte strength.) the influence of sediment particle size on flocs sedimentation and sediment concentration is much greater than that of electrolyte strength. Electrolyte conditions are closely related. 6) the formula of flocculant sedimentation velocity fitted in this paper is more in agreement with the measured results.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV149

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