本文選題：海底管線　切入點(diǎn)：自沉過程　出處：《天津大學(xué)》2014年碩士論文

【摘要】：海底管線是連接油井與平臺、平臺與陸上儲運(yùn)設(shè)施的油氣輸送工具,具有安全、穩(wěn)定、經(jīng)濟(jì)、輸送量大等優(yōu)點(diǎn),是海洋油氣輸運(yùn)系統(tǒng)的重要組成部分。海底管線的鋪設(shè)方式分為裸置與埋置兩種,不論采取何種方式,海底管線在鋪設(shè)后,由于自重作用將開始自沉過程,管線逐漸嵌入海床土體,最終達(dá)到管土平衡的狀態(tài)。由于海底環(huán)境與陸上不同,在自沉過程中,海底管線受多種荷載的聯(lián)合影響,易產(chǎn)生較大的變形而失穩(wěn),造成巨大的經(jīng)濟(jì)損失和環(huán)境污染,因此海底管線的安全性和穩(wěn)定性在海洋油氣開發(fā)中尤為重要。通過有限元軟件ABAQUS,應(yīng)用Mohr-Coulomb本構(gòu)關(guān)系,建立深海海底管土相互作用模型,模擬海底裸置與埋置管線的自沉過程。通過設(shè)置初始地應(yīng)力平衡,管土接觸,重力、浮力施加,土體排水固結(jié)等分析步,計(jì)算裸置和埋置管線、土體豎直方向的位移,并通過大量計(jì)算,探究管線和土體相關(guān)參數(shù)的變化對自沉過程的影響。計(jì)算結(jié)果顯示,對于裸置管線,土體呈現(xiàn)沉降趨勢,且參數(shù)的改變使土體越容易發(fā)生塑性屈服,土體的豎直方向位移量越大;對于埋置管線,土體呈現(xiàn)隆起趨勢,且當(dāng)管線埋深較淺、管線上方土體重量不大時(shí),參數(shù)的改變使管線的平均密度與周圍土體的密度相差越大、土體越容易發(fā)生塑性屈服,土體的豎直方向位移量越大。同時(shí)通過在裸置管線模型中設(shè)定生死單元的方式使部分土體失效,模擬海底懸跨管線的自沉過程,并探究懸跨長度對自沉過程的影響。計(jì)算結(jié)果顯示,當(dāng)管線懸跨長度較小時(shí),土體豎直方向位移與管線未懸跨時(shí)的數(shù)值相接近,略有增長;一旦管線懸跨長度過大,管線兩端支撐土體即被壓潰,管線將產(chǎn)生大變形,十分危險(xiǎn)。因此在海底管線安裝與維護(hù)中,一定要采取有效措施降低懸跨長度,保證管線運(yùn)營安全。
[Abstract]:Submarine pipeline is an oil and gas transportation tool connecting oil well and platform, platform and onshore storage and transportation facilities. It has the advantages of safety, stability, economy and large transportation capacity. It is an important part of offshore oil and gas transportation system.The laying mode of submarine pipeline can be divided into naked and buried. No matter what way, after laying the submarine pipeline, the self-sinking process will begin due to self-gravity, and the pipeline will be embedded into the seabed soil gradually, and finally reach the state of pipe and soil balance.Because the submarine environment is different from the land, during the process of self-sinking, the submarine pipeline is affected by the combination of various loads, and it is easy to produce large deformation and instability, resulting in huge economic losses and environmental pollution.Therefore, the safety and stability of submarine pipelines are particularly important in offshore oil and gas development.By using the finite element software Abaqus and applying the Mohr-Coulomb constitutive relation, the model of the deep sea bottom tube-soil interaction is established, and the self-sinking process of the submarine bare and buried pipelines is simulated.By setting the initial geostress balance, pipe-soil contact, gravity, buoyancy, soil drainage and consolidation, the displacement of the bare and buried pipelines and the vertical direction of the soil is calculated, and a large number of calculations are carried out.To explore the influence of pipeline and soil related parameters on self-sinking process.The calculation results show that for the bare pipeline, the soil presents a settlement trend, and the change of parameters makes the soil more prone to plastic yield, and the vertical displacement of the soil is larger; for the buried pipeline, the soil shows a uplift trend.When the buried depth of the pipeline is shallow and the weight of the soil above the pipeline is small, the variation of the parameters makes the difference between the average density of the pipeline and the surrounding soil mass greater, the more prone to plastic yield of the soil, the larger the vertical displacement of the soil.At the same time, by setting the birth and death element in the model of bare pipeline, the partial soil is invalid, and the self-sinking process of submarine overhanging pipeline is simulated, and the influence of the length of suspended span on the self-sinking process is explored.The calculation results show that the vertical displacement of soil is close to that of the pipeline when the length of the suspended span is small, and increases slightly; once the length of the suspended span of the pipeline is too large, the soil supported at both ends of the pipeline will be crushed.The pipeline will be deformed and very dangerous.Therefore, in the installation and maintenance of submarine pipelines, effective measures must be taken to reduce the length of suspension span to ensure the safety of pipeline operation.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：P756.2;TE832

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