生物作用下排水管道沉积物起动规律研究

发布时间：2018-03-21 15:51

本文选题：起动标准　切入点：无机沙　出处：《浙江大学》2017年硕士论文　论文类型：学位论文

【摘要】：本文通过归纳排水管道因淤积产生的危害,整理前人关于管道沉积物自身物理特性、内部生化反应以及在各水力条件下沉积、输移的研究,针对研究中存在的一些不足,考虑管道沉积物所存在的不均匀性、含有大量有机质等特点,本文采用微观观测和宏观冲刷试验相结合的方式,从以下几个方面对排水管道沉积物起动规律展开研究:(1)选取真实管道沉积物,分析排水管道沉积物的堆积密度、颗粒级配、有机质含量等物理特性,探寻不同水流强度下试样起动情况,并尝试提出用特征粒径作为泥沙起动判断标准的方法。结果显示沉积物具有非均匀性,在分级水流强度下分组起动。当达到临界起动的剪切应力时,起动组分的推移质中值粒径约在试样整体中处于d54～d63的范围。可用试样整体的d60作为临界起动的判别粒径。(2)选取沉积现象不明显的无机石英沙作为研究材料,通过配制营养液、引入微生物,并创造良好的温度、溶解氧环境,观察在外源有机物培养下生物活动对试样产生的影响,包括采用扫描电子显微镜(Scanning Electron Microscopy,SEM)和激光共聚焦显微镜(Laser Scanning Confocal Microscope,LSCM)从微观角度观察无机沙表面形貌的变化以及通过明渠直流水槽的冲刷试验从宏观角度研究试样冲蚀起动规律的变化。结果表明,生物活动在沙床表面和颗粒间生成生物膜,减小了表面粗糙度,增强了颗粒间的联结,使整体抗侵蚀能力提高,临界剪切应力增强;但在后期会因生物膜老化而减弱。定量分析生物膜的增强效果,并对希尔兹公式和起动概率做出修正。(3)选取真实管道沉积物作为研究材料,通过湿筛重构其颗粒间关系,观察在适宜的温度、溶氧环境下,沉积物内部生物活动对试样产生的影响,包括通过SEM、LSCM从微观角度观察试样表面形貌的变化、通过X射线计算断层扫描(X-ray Computed Tomograpgy,XCT)观察试样内部结构的改变以及通过明渠直流水槽的冲刷试验从宏观角度研究试样冲蚀起动规律的变化。结果表明,有别于无机沙营养液培养,沉积物中的生物活动不仅产生生物膜,有助于增强抗侵蚀的能力,但同时也消耗有机物、产生气体,使沉积物整体膨胀,削弱了抗侵蚀的能力。在现有理论的基础上,定量分析生物活动对不同有机质含量沉积物的影响。
[Abstract]:Through summing up the harm caused by siltation of drainage pipeline, this paper collates the previous researches on the physical characteristics, internal biochemical reaction, deposition and transportation under various hydraulic conditions of pipeline sediment, aiming at some shortcomings in the research. Considering the heterogeneity of pipeline sediment and the large amount of organic matter, this paper combines microscopic observation with macroscopic scour test. In this paper, the starting law of sediment in drainage pipeline is studied in the following aspects. (1) selecting real pipeline sediment, analyzing the physical characteristics of sediment accumulation density, particle gradation, organic matter content, etc. This paper probes into the starting condition of the sample under different flow intensity, and tries to put forward the method of using the characteristic particle size as the criterion of sediment starting. The results show that the sediment is non-uniform. When the shear stress of critical starting is reached, The median particle size of bed load of the starting component is approximately within the range of d54 / d63 in the whole sample. Using d60 of the whole sample as the critical starting particle size, the inorganic quartz sand which is not obvious deposition phenomenon is selected as the research material, and the nutrient solution is prepared. Microbes were introduced, and good temperature and dissolved oxygen environment were created to observe the effects of biological activities on the samples under the culture of exogenous organic compounds. Scanning electron microscope (SEM) and laser confocal microscope (Laser Scanning Confocal microscopeLSCM) were used to observe the surface morphology of inorganic sand from a microscopic point of view. The results show that, Biological activity forms biofilm on the surface of sand bed and between particles, which reduces the surface roughness, strengthens the connection between particles, enhances the overall anti-erosion ability and enhances the critical shear stress. However, the biofilm aging will weaken in the later stage. Quantitative analysis of the enhancement effect of biofilm is made, and the Shields formula and starting probability are revised. The real pipeline sediment is selected as the research material, and the relationship between the particles is reconstructed by wet sieve. The effects of biological activities within sediment on the specimen were observed at appropriate temperature and dissolved oxygen environment, including the microscopic observation of the surface morphology of the sample from the point of view of SEMN LSCM. X-ray Computed TomograpgyXCTs were used to observe the change of internal structure of the sample and to study the change of the erosion starting law of the sample from the macroscopic point of view through the scour test of the open channel direct current flume. The results show that it is different from the culture of inorganic sand nutrient solution. Biological activities in sediments not only produce biofilms that help to enhance their ability to resist erosion, but also consume organic matter, produce gases, cause the sediment to expand as a whole, and weaken its ability to resist erosion. The effects of biological activities on the sediments with different organic matter contents were quantitatively analyzed.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU992

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