| Summary: | 碩士 === 逢甲大學 === 水利工程所 === 94 === Settling behaviors of stagnant muddy lake is investigated in this study. A large-size water tank and three settling columns with different size were used as settling facilities. Three kinds of material, which including standard kaolin and clay sampled from Shimen reservoir and Agongdian reservoir, are used, respectively, to mix with water and become muddy water with different concentration as the experimental material. During an experiment the settling behaviors were recorded and concentration profiles at different time were taken. It is found that framework phenomena will not arise in the water without anion and cation, even if the initial concentration of the muddy water is higher than the critical concentration that framework occur. When framework arises, it is not necessarily that a concentration interval with uniform settling velocity occurs. Framework interval with uniform settling velocity can occur when the initial concentration is higher than a specific concentration. According to our experimental results, the minimum initial concentration which framework occurs for Shimen clay is 25g/L; and 60g/L is the minimum concentration for framework interval with uniform velocity occurs. The minimum initial concentration that muddy water settling without particle sorting and large particles do not settle first is 180g/L. For scale effects of settling column, lateral size do not affect the settling velocity and the concentration profile in the stagnant case. The effect of vertical scale on settling behavior is the duration of settling for framework interval with uniform velocity. No matter what size the settling column is, the trend of settling velocity curve is all the same. Once the layer with uniform concentration of muddy water disappears, the framework interval with uniform settling velocity comes to an end.
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