本文選題：疏浚 + 懸浮物　； 參考：《重慶交通大學(xué)》2014年碩士論文

【摘要】：為了維護(hù)航道的通航標(biāo)準(zhǔn)及改善泥沙淤積狀況，一般需要定期對航道進(jìn)行疏浚作業(yè)，然而在施工過程中容易因泥沙攪動、外泄而產(chǎn)生懸浮泥沙，并在水流作用下擴(kuò)散到周邊區(qū)域，導(dǎo)致以施工區(qū)為中心的附近水域混濁度增加，同時，泥沙中攜帶的有毒、有害物質(zhì)也會使水體的使用質(zhì)量下降�；诖�，在疏浚環(huán)境影響評價過程中，針對不同的水域及水質(zhì)污染的特點(diǎn)，選擇相應(yīng)的底泥水質(zhì)模型對疏浚導(dǎo)致的懸浮污染物的影響范圍作出預(yù)測及評估，從而選擇正確的清淤處理方案，是非常必要的，同時對水環(huán)境的保護(hù)以及環(huán)保疏浚的開展具有十分重要的指導(dǎo)意義。 本文基于FLUENT軟件，模擬工程區(qū)域泥沙懸浮擴(kuò)散狀況；并以數(shù)值模擬的預(yù)測結(jié)果為依據(jù)，分析比對兩種疏浚方式（絞吸式和抓斗式）在不同疏浚期下（枯水期和雨水期）懸浮泥沙的濃度分布及擴(kuò)散范圍，確定最佳施工方案。通過對絞吸式溢流沉淀池中泥沙沉降過程的模擬，比對分析不同進(jìn)水口流速下對泥沙的沉降效果及出水水質(zhì)的影響，揭示泥沙顆粒的沉降規(guī)律。 研究結(jié)果表明：通過兩種疏浚形式（絞吸式和抓斗式）分別在汛期和旱期施工時懸浮擴(kuò)散對施工區(qū)域的影響對比表明，沿三維方向所選大部分監(jiān)測斷面在旱期施工時所產(chǎn)生的泥沙濃度值是低于汛期的。以一個疏浚點(diǎn)所產(chǎn)生的懸浮擴(kuò)散為基點(diǎn)，通過折算出超水質(zhì)標(biāo)準(zhǔn)的擴(kuò)散面積對比分析表明，汛期均大于旱期，即利用兩種疏浚形式分別進(jìn)行疏浚作業(yè)時，在汛期施工所產(chǎn)生的泥沙懸浮擴(kuò)散對施工區(qū)周邊水域的影響比旱期更大，即確定旱期為最佳疏浚期。根據(jù)兩種疏浚形式下在最佳施工期內(nèi)各個監(jiān)測斷面最大泥沙濃度和區(qū)域平均濃度的對比分析表明，在所選監(jiān)測斷面z=10、20、30、40、50，抓斗式疏浚方式無論從泥沙濃度最大值還是區(qū)域濃度平均值均高于絞吸式疏浚方式，在斷面y=-9、-7、-5、-3、-1及x=14、13、12、11上，由于絞吸式釋放源強(qiáng)比抓斗式更大，除靠近疏浚源附近斷面y=-9及x=14處采用抓斗式挖泥船疏浚時泥沙濃度最大值相比于絞吸式較小外，其余監(jiān)測斷面無論從泥沙濃度最大值還是區(qū)域濃度平均值均大于絞吸式疏浚方式，即確定絞吸式疏浚為最佳疏浚形式。 基于FLUENT軟件對絞吸式疏浚方式下泥水處理構(gòu)筑物溢流沉淀池中泥沙沉降過程進(jìn)行模擬，并選取四個備選流速，對不用進(jìn)水口流速下泥沙沉降效果及出水泥沙濃度進(jìn)行比對分析，，結(jié)果表明：隨著進(jìn)口水水流流速的減小，沉淀池內(nèi)的異重流、短流現(xiàn)象較嚴(yán)重，導(dǎo)致泥沙顆粒沉降效果受到影響，出水水質(zhì)較差；隨著進(jìn)水口水流流速的增加，沉淀池進(jìn)水口處異重流的強(qiáng)度得到改善，但沉淀池內(nèi)水力停留時間縮短，沉淀效果也會受到影響。所以在進(jìn)水口流速的選取上應(yīng)綜合考慮上述兩方面的因素，既要從流態(tài)上減輕異重流的影響，還需從理論上考慮泥沙顆粒在池內(nèi)的水力停留時間，才能從本質(zhì)上改善泥沙顆粒的沉降效果。 本研究針對性較強(qiáng)，為長江航道疏浚工程的開展提供了理論支持，并為三峽航道綠色施工技術(shù)研究提供了技術(shù)保障，研究具有重要的使用價值和現(xiàn)實(shí)意義。
[Abstract]:In order to maintain the navigation standard of the channel and improve the silt condition, it is generally necessary to dredge the channel regularly. However, in the process of construction, the suspended sediment is easily caused by the agitation of sediment, and it is diffused to the surrounding area under the action of water, which leads to the increase of turbidity in the surrounding waters of the construction area and the sediment in the sediment. In the process of environmental impact assessment of dredging, according to the characteristics of different water and water pollution, the corresponding sediment water quality model is selected to predict and evaluate the influence range of the suspended pollutants caused by dredging, so as to select the correct clearing treatment side. The case is very necessary, and is of great guiding significance for the protection of water environment and the development of environmental dredging.
Based on the FLUENT software, this paper simulated the sediment suspension diffusion in the engineering area, and based on the prediction results of the numerical simulation, analyzed the concentration distribution and spread range of the suspended sediment in the two dredging modes (winch and grab) during the different dredging period (the dry period and the rainwater period), and determined the best construction scheme. The simulation of sediment settling process in a flow sedimentation tank is compared to analyze the effect of sediment settlement and water quality at different inlet flow velocity, and the settlement law of sediment particles is revealed.
The results show that the influence of the suspension diffusion on the construction area during the construction of two types of dredging (winch and grab) during the construction of the flood season and the drought period, respectively, shows that the concentration of most of the monitoring sections along the three dimensional direction is lower than the flood season. For the base point, the contrast analysis of the diffusion area of the converted water quality standard shows that the flood season is greater than the drought period, that is, when the dredging operation is carried out by two kinds of dredging, the influence of the suspended sediment diffusion on the surrounding waters of the construction area is greater than that in the drought period, that is to determine that the period of the drought is the best dredging period. According to the two dredging period, the dredging period is determined as the best dredging period. The comparison and analysis of the maximum sediment concentration and regional average concentration of each monitoring section in the best construction period shows that in the selected monitoring section z=10,20,30,40,50, the method of grab dredging is higher than the method of dredging from the maximum value of the sediment concentration or the regional concentration, and in the section y=-9, -7, -5, -3, -1 and x=14,13,12,11 As the suction type release source is stronger than the grab type, the maximum value of the sediment concentration is smaller than that of the winch in the dredging of the grab dredger near the section y=-9 and x=14 near the dredging source, and the maximum value of the sediment concentration or the average value of the regional concentration is greater than that of the stranded suction dredging, that is to determine the suction suction. Type dredging is the best form of dredging.
Based on the FLUENT software, the sediment deposition process in the overflow sedimentation tank of the mud water treatment structure under the suction dredging is simulated, and four alternative flow velocities are selected to compare the sediment settlement effect and the cement sand concentration at the flow velocity without the inlet. The results show that with the decrease of the flow velocity of the imported water flow, the difference in the sedimentation tank is different. Heavy flow and short flow phenomenon are serious, which results in the effect of sedimentation of sediment particles, and the water quality is poor. With the increase of flow velocity of the inlet, the strength of the gravity flow at the inlet of the sedimentation tank is improved, but the hydraulic retention time in the sedimentation tank is shortened and the precipitation effect will be affected. Therefore, the selection of the flow velocity of the intake should be integrated. Considering the above two factors, we should not only reduce the influence of the flow in the flow state, but also consider the hydraulic retention time of the sediment particles in the pool theoretically, in order to improve the sedimentation effect of the sediment particles in essence.
This study is more pertinent and provides theoretical support for the development of the dredging project of the Yangtze River channel, and provides technical support for the green construction technology research of the Three Gorges waterway. The research is of great use value and practical significance.
【學(xué)位授予單位】：重慶交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：X82;U616

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本文編號：1972161