【作者】 武君；

【导师】 仵彦卿；

【作者基本信息】 上海交通大学 ， 环境科学， 2008， 博士

【摘要】 尾矿坝的安全稳定性对周围生态环境和人民生命财产安全都具有非常重要的影响。淤堵的发生会导致尾矿坝的排水不畅,从而影响其稳定性与安全性。淤堵的形成机理与控制等的研究是解决这一问题的关键。本文在国家自然科学基金“变饱和介质中变形-渗流-化学过程耦合模型研究”（批准号:10572090）资助下,通过现场调查与观测、实验室ICP-AES、XRD和SEM-EDS分析、室内砂柱试验等方法,探讨了引起尾矿坝淤堵的主要物质、淤堵形成机理、淤堵过程与渗流之间的相互作用,取得了以下主要研究成果:（1）对金堆城钼业公司栗西尾矿坝进行的现场调查结果表明,尾矿坝库水及辐射井出水主要为SO₄^2-—Ca²⁺和SO₄^2--HCO₃^-—Ca²⁺型水,pH值为6.8-7.5。淤堵物质中铁元素的含量最高,2个淤堵样品铁元素含量分别为54.35%和40.24%。淤堵物质主要是氢氧化铁及其转化产物组成的混合物质,结构松散,并呈团簇状分布。（2）亚铁氧化试验结果表明,亚铁的氧化服从一级动力学方程,氧化速率与pH值联系密切,pH值越高,氧化速率越快;亚铁初始浓度越大,氧化速率也越快。（3）以不同粒径石英砂（5#砂,粒径0.20-0.50 mm;6#砂,粒径0.10-0.20 mm;8#砂,粒径0.076-0.15 mm）为填充介质,通过上流式运行方式向试验柱内连续输入亚铁溶液,同时不断调节溶液层pH值在6.8-7.5间变动,在自然供氧条件下,溶液层中的亚铁不断发生氧化反应,逐渐生成淤堵物质,淤堵物质不断积累堵塞出水口是引起淤堵的主要原因。当输入的亚铁溶液浓度为100 mg/L时,5#石英砂柱、6#石英砂柱及8#石英砂柱分别经过20、23和26天运行,淤堵发生;当输入的亚铁溶液浓度为10 mg/L时,5#石英砂柱、6#石英砂柱及8#石英砂柱分别经过54、51和77天运行,淤堵发生。试验结果表明,淤堵的发生与亚铁输入浓度有关,浓度越高,淤堵发生的时间越短;同时淤堵的发生也与填充介质性能存在一定关系。各淤堵试验过程中,渗透系数只在最后阶段发生突变,显著降低。同时进行了尾矿砂柱淤堵试验,当输入的亚铁溶液浓度为100 mg/L和10 mg/L时,分别经过42和105天运行,淤堵发生。试验过程呈现两个变化阶段:第一阶段尾矿砂层缓冲能力不断饱和;第二阶段亚铁不断氧化生成淤堵物质,导致淤堵发生。渗透系数的变化类似于石英砂柱淤堵试验。各淤堵试验结束后对淤堵物质进行分析,淤堵物质铁元素含量均高于37%。分析结果表明淤堵物质呈松散的团簇状结构,氢氧化铁是其初始主要成分。（4）采用交替式输入溶液运行方法进行的淤堵试验中,弥散系数的变化可分为两个阶段。第一阶段随着淤堵的不断发生,淤堵物质的积累造成多孔介质系统异质性增强,引起弥散系数逐渐增大;第二阶段,淤堵物质在多孔介质中的积累逐渐达到相对稳定平衡的状态,孔隙分布又逐渐趋于均匀,导致弥散作用减弱,相应地弥散系数从最大逐渐减小。（5）假定亚铁离子已经氧化形成氢氧化铁淤堵物质,开展了一系列砂柱试验,获得了浓度与渗透系数、弥散系数等量之间的关系,建立了多孔介质淤堵过程的渗流和溶质运移耦合模型。（6）对6#石英砂柱淤堵试验出水的亚铁、总铁和可过滤性总铁的浓度变化尝试采用混沌理论和分形理论进行了模拟。更多还原

【Abstract】 The safety and stability of the tailings dam are very critical for the ecosystem of the surroundings and the life and fortune of the people. However, clogging of the tailings dam will bring about difficulty for water drainage to have great influence on the stability and safety of the tailings dam. Therefore, the mechanism and control of the clogging are of important value in solving this problem. Financially supported by“A Model of CoupledDeformation-Seepage-Chemical Processes in Variably Saturated Media”（National Natural Science Foundation of China, Grant No. 10572090）, this dissertation has studied the main clogging materials, the mechanism of the clogging, and the interaction between the clogging and seepage by carrying out the field investigation and laboratory sand column experiments and using analysis methods such as ICP-AES, XRD and SEM-EDS, and the main research results are as follows.（1） The results of field investigation on Lixi tailings dam of Jinduicheng Molybdenum Group Mining Corporation show the water types of the samples from the tailing pond and the effluent of the radial wells are SO₄^2-—Ca²⁺ and SO₄^2--HCO₃^-—Ca²⁺. The pH of the samples ranges from 6.8 to 7.5. Iron is the dominant element in the clogging materials, and the contents of two clogging samples are 54.35% and 40.24%, respectively. The analysis results show that the clogging materials are a mixture of iron hydroxide and its converted products, and the clogging materials commonly exist in an amorphous form with a cluster microstructure when viewed under SEM.（2） The results of ferrous iron oxidation experiments show that the ferrous iron oxidation follows first order kinetics, and the oxidation process is strongly dependent on pH, a higher pH resulting in a higher oxidation rate. Moreover, results also indicate that a higher concentration of ferrous iron causes a higher oxidation rate.（3） Columns were packed with different clean quartz sands including 5# sand （particle size 0.20-0.50 mm）, 6# sand （particle size 0.10-0.20 mm）, and 8# sand （particle size 0.076-0.15 mm）, respectively. The ferrous iron solution was continuously pumped using a peristaltic pump from the bottom to the top of the experimental column. The results of clogging experiments using quartz sand columns indicate that ferrous iron in the solution layer is oxidized and the clogging materials are gradually formed under the conditions of adjusting the pH of the solution layer as 6.8-7.5 and the natural oxygen supply. The clogging materials accumulated and clogged the outlet to cause the clogging according to the results of the experiments. When the inlet concentration of ferrous iron solution was 100 mg/L, clogging completely occurred for 5# sand column experiment, 6# sand column experiment, and 8# sand column experiment operated for 20, 23, and 26 days, respectively. When the inlet concentration of ferrous iron solution was 10 mg/L, clogging completely occurred for 5# sand column experiment, 6# sand column experiment, and 8# sand column experiment operated for 54, 51, and 77 days, respectively. The results show that the occurrence of clogging bears relation with the inlet concentration of ferrous iron solution, a higher concentration resulting in a shorter stage to occur clogging. Moreover, the occurrence of clogging is in connection with the properties of porous media. The change in the hydraulic conductivity of different clogging experiments has the similar trend that the hydraulic conductivity decreases significantly at the last stage.Furthermore, the clogging experiments of tailings sand column were carried out. When the inlet concentration of ferrous iron solution was 100 mg/L and 10 mg/L, clogging completely occurred for tailings sand column experiments operated for 42 and 105 days, respectively. Results have shown that there are two stages during the experiment, the buffer capacity of the tailings sand layer is gradually attenuated at the first stage, and then the ferrous iron is continuously oxidized into the clogging materials to cause the clogging at the second stage. The change in the hydraulic conductivity of tailings sand column experiments is similar to that of quartz sand column experiments.Clogging materials were analyzed after clogging experiments, and iron contents of clogging materials are higher than 37%. The clogging materials are found to exist in the loose cluster microstructure, and iron hydroxide may be the main initial compound according to the results of XRD and SEM.（4） The results of the tracer tests indicate that there are two stages for the change in the dispersion coefficient during the clogging experiment by alternately introducing the solution. The clogging materials accumulate in the porous media to result in stronger heterogeneity, so the dispersion coefficient increases at the first stage. When the accumulation of clogging materials is gradually relatively stable, and pore distribution becomes homogeneous, so the dispersion coefficient decreases at the second stage.（5） Based on the hypothesis that the ferrous iron has been oxidized into the iron hydroxide, a series of sand column experiments are carried out. The relationship between concentration and other parameters such as the hydraulic conductivity, the dispersion coefficient and so on is acquired. The flow and transport models during clogging process are coupled according to the sand column experiment results.（6） The chaos theory and fractal theory are applied to simulate the change in the concentrations of ferrous iron, total iron and filtered total iron of the effluent during the clogging experiments of 6# quartz sand column.更多还原