本文選題：起動標準　切入點：無機沙　出處：《浙江大學》2017年碩士論文　論文類型：學位論文

【摘要】：本文通過歸納排水管道因淤積產生的危害,整理前人關于管道沉積物自身物理特性、內部生化反應以及在各水力條件下沉積、輸移的研究,針對研究中存在的一些不足,考慮管道沉積物所存在的不均勻性、含有大量有機質等特點,本文采用微觀觀測和宏觀沖刷試驗相結合的方式,從以下幾個方面對排水管道沉積物起動規(guī)律展開研究:(1)選取真實管道沉積物,分析排水管道沉積物的堆積密度、顆粒級配、有機質含量等物理特性,探尋不同水流強度下試樣起動情況,并嘗試提出用特征粒徑作為泥沙起動判斷標準的方法。結果顯示沉積物具有非均勻性,在分級水流強度下分組起動。當達到臨界起動的剪切應力時,起動組分的推移質中值粒徑約在試樣整體中處于d54～d63的范圍。可用試樣整體的d60作為臨界起動的判別粒徑。(2)選取沉積現(xiàn)象不明顯的無機石英沙作為研究材料,通過配制營養(yǎng)液、引入微生物,并創(chuàng)造良好的溫度、溶解氧環(huán)境,觀察在外源有機物培養(yǎng)下生物活動對試樣產生的影響,包括采用掃描電子顯微鏡(Scanning Electron Microscopy,SEM)和激光共聚焦顯微鏡(Laser Scanning Confocal Microscope,LSCM)從微觀角度觀察無機沙表面形貌的變化以及通過明渠直流水槽的沖刷試驗從宏觀角度研究試樣沖蝕起動規(guī)律的變化。結果表明,生物活動在沙床表面和顆粒間生成生物膜,減小了表面粗糙度,增強了顆粒間的聯(lián)結,使整體抗侵蝕能力提高,臨界剪切應力增強;但在后期會因生物膜老化而減弱。定量分析生物膜的增強效果,并對希爾茲公式和起動概率做出修正。(3)選取真實管道沉積物作為研究材料,通過濕篩重構其顆粒間關系,觀察在適宜的溫度、溶氧環(huán)境下,沉積物內部生物活動對試樣產生的影響,包括通過SEM、LSCM從微觀角度觀察試樣表面形貌的變化、通過X射線計算斷層掃描(X-ray Computed Tomograpgy,XCT)觀察試樣內部結構的改變以及通過明渠直流水槽的沖刷試驗從宏觀角度研究試樣沖蝕起動規(guī)律的變化。結果表明,有別于無機沙營養(yǎng)液培養(yǎng),沉積物中的生物活動不僅產生生物膜,有助于增強抗侵蝕的能力,但同時也消耗有機物、產生氣體,使沉積物整體膨脹,削弱了抗侵蝕的能力。在現(xiàn)有理論的基礎上,定量分析生物活動對不同有機質含量沉積物的影響。
[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.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU992

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相關期刊論文 前10條

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本文編號：1644532