本文選題：多年凍土區(qū) + 埋地式輸氣管道�。� 參考：《蘭州交通大學(xué)》2017年碩士論文

【摘要】：我國凍土區(qū)域分布較為廣泛,作為世界第三大凍土國,凍土區(qū)面積約占國土面積的75%。在這些凍土區(qū)域中,尤其是多年凍土區(qū),儲(chǔ)藏著豐富的石油天然氣資源。隨著我國經(jīng)濟(jì)社會(huì)不斷向前發(fā)展,因埋地式管道有著成本相對(duì)較低、運(yùn)量大、占地少、建設(shè)周期短等優(yōu)點(diǎn),在多年凍土區(qū)敷設(shè)埋地式輸氣管道作為目前乃至今后長距離輸送油氣資源的主要方式仍將不可避免的要穿越這些區(qū)域。然而,在多年凍土區(qū),尤其是在青藏高原這樣平均海拔高、多年凍土面積分布廣泛、多年凍土層厚度大、自然條件十分惡劣、地質(zhì)條件十分復(fù)雜的多年凍土區(qū)敷設(shè)埋地式正溫輸氣管道,國內(nèi)尚無成熟的經(jīng)驗(yàn)技術(shù)以供借鑒參考,同時(shí)對(duì)于多年凍土區(qū)埋地式管道與其周圍多年凍土之間相互作用機(jī)理的研究仍處于逐步探索階段,管道周圍多年凍土的力學(xué)特征、熱穩(wěn)定性及管道的工程特性是研究多年凍土區(qū)埋地式正溫輸氣管道工程的關(guān)鍵問題所在。本文以青藏高原多年凍土區(qū)正溫埋地式輸氣管道某區(qū)段管道及周圍土體為研究對(duì)象,針對(duì)該區(qū)段沿線多年凍土退化引起的病害,結(jié)合該區(qū)段多年凍土特征,考慮未來氣候升溫環(huán)境因素及傳熱學(xué)基本理論,利用大型有限元數(shù)值計(jì)算軟件ANSYS對(duì)不同管道中心埋深、不同管內(nèi)介質(zhì)輸送溫度以及有無保溫措施并考慮冰水相變過程條件下管道周圍土體的非穩(wěn)態(tài)溫度場分布情況進(jìn)行了數(shù)值求解,得到了不同條件下管道周圍土體的溫度場分布趨勢(shì),同時(shí)也利用ANSYS熱力間接耦合方法計(jì)算了管道在不同條件下其內(nèi)部等效應(yīng)力的分布情形。本文的主要結(jié)論如下:(1)通過對(duì)不同條件下高海拔多年凍土區(qū)埋地式正溫輸氣管道周圍土體溫度場的數(shù)值計(jì)算,分析發(fā)現(xiàn)該區(qū)段多年凍土熱穩(wěn)定性較差,埋設(shè)正溫輸氣管道對(duì)管道周圍多年凍土賴以保持穩(wěn)定的凍土環(huán)境威脅極大;(2)管道中心埋深對(duì)管道周圍多年凍土的溫度場分布規(guī)律影響較大,一般來說,在管內(nèi)介質(zhì)管內(nèi)介質(zhì)輸送溫度一定時(shí),管道中心埋深越大,在計(jì)算時(shí)間內(nèi)管道底部的多年凍土融化深度也就越大:管道中心埋深分別為2.0m、2.5m、3.0m時(shí),在管內(nèi)介質(zhì)輸送溫度為10℃和16℃條件下,計(jì)算第50年其管道底部的多年凍土融化深度分別為2.76m、3.21m、3.68m和2.84m、3.35m、3.76m,在正溫輸氣管道設(shè)計(jì)、施工敷設(shè)時(shí)管道中心埋深要經(jīng)濟(jì)、合理;(3)隨著管內(nèi)介質(zhì)管內(nèi)介質(zhì)輸送溫度的升高,管道底部下方土體最大融化厚度也就越大:管道中心埋深2.0m時(shí),在管內(nèi)介質(zhì)輸送溫度為10℃和16℃條件下,管道底部下方土體最大融化厚度分別為43cm和50cm;管道中心埋深2.5m時(shí),在管內(nèi)介質(zhì)輸送溫度為10℃和16℃條件下,管道底部下方土體最大融化厚度分別為38cm和47cm;管道中心埋深3.0m時(shí),在管內(nèi)介質(zhì)輸送溫度為10℃和16℃條件下,管道底部下方土體最大融化厚度分別為35cm和43cm;在實(shí)際操作中應(yīng)控制管內(nèi)介質(zhì)輸送溫度,盡量避免過高的管內(nèi)介質(zhì)輸送溫度;(4)使用45mm厚的聚氨酯泡沫作為管道外壁保溫措施,可以有效減小正溫輸氣管道熱量對(duì)管道周圍多年凍土的熱擾動(dòng),直接表現(xiàn)為有保溫措施時(shí)管道周圍多年凍土的融化范圍較無保溫措施時(shí)極小:45mm厚的聚氨酯泡沫作為管道外壁保溫措施,管道中心埋深2.0m時(shí),在管內(nèi)介質(zhì)輸送溫度為10℃和16℃條件下,管道底部下方土體最大融化厚度分別為0mm和43.7mm;管道中心埋深2.5m時(shí),在管內(nèi)介質(zhì)輸送溫度為10℃和16℃條件下,管道底部下方土體最大融化厚度分別為0mm和35.3mm;管道中心埋深3.0m時(shí),在管內(nèi)介質(zhì)輸送溫度為10℃和16℃條件下,管道底部下方土體最大融化厚度分別為0mm和30.5mm;(5)在埋地式正溫輸氣管道敷設(shè)、運(yùn)營的前10~20年內(nèi),正溫管道熱量對(duì)管道周圍多年凍土的熱擾動(dòng)最大,在此期間應(yīng)注意加強(qiáng)管道周圍土體的溫度監(jiān)測(cè)與管道維護(hù);(6)不同條件下,由于管道內(nèi)部壓力、自重、上覆土體自重以及由于周圍土體溫度變化產(chǎn)生的荷載在管道中產(chǎn)生的等效應(yīng)力最大值位于管道底部內(nèi)側(cè);(7)不同管道中心埋深時(shí)其管道底部內(nèi)側(cè)等效應(yīng)力隨計(jì)算時(shí)間的增加逐漸增大,等效應(yīng)力最大值在計(jì)算的第30年;(8)在管道管內(nèi)介質(zhì)輸送溫度為16℃、無保溫措施情況下,管道中心埋深越大,由于管道內(nèi)部壓力、自重、上覆土體自重以及由于周圍土體溫度變化產(chǎn)生的荷載在管道中產(chǎn)生的等效應(yīng)力也就越大;在計(jì)算的第30年,管道中心埋深3.0m情況下管道底部內(nèi)側(cè)等效應(yīng)力為203MPa,管道中心埋深為2.5m、2.0m時(shí)其等效應(yīng)力分別為172MPa、149MPa,分別是管道中心埋深為2.0m、2.5m時(shí)等效應(yīng)力的1.36倍和1.18倍;(9)管道中心埋深相同、管道管內(nèi)介質(zhì)輸送溫度為16℃情況下,采取45mm聚氨酯泡沫作為保溫措施可以有效減小由于管道內(nèi)部壓力、自重、上覆土體自重以及由于周圍土體溫度變化產(chǎn)生的荷載在管道中產(chǎn)生的等效應(yīng)力,以管道中心埋深3.0m時(shí)管道底部內(nèi)側(cè)的等效應(yīng)力值為135MPa最大,而管道中心埋深為2.0m、2.5m時(shí)其等效應(yīng)力分別為78.3MPa和94.7MPa,分別是無保溫措施時(shí)其管道底部內(nèi)側(cè)等效應(yīng)力的兩種管道中心埋深的52.6%、55.1%和58.7%。
[Abstract]:The permafrost region is widely distributed in China. As the third largest permafrost in the world, the 75%. of the permafrost area accounts for the land area. In these frozen soil areas, especially in the permafrost regions, the rich oil and natural gas resources are stored. With the continuous development of the economy and society in China, the buried pipeline has relatively low cost and a large amount of transportation. There are few advantages, such as short period of construction and short construction period. In permafrost area laying buried gas pipeline as the main way of transporting oil and gas in long distance will inevitably pass through these areas. However, in permafrost regions, especially in the Qinghai Tibet Plateau, the plateau is all above sea level, and permafrost area is widely distributed for many years. It is still in the stage of gradual exploration for the study of the interaction mechanism between buried pipelines and permafrost around permafrost regions, which have no mature experience technology for reference in the permafrost regions with large soil thickness, very bad natural conditions and complicated geological conditions. The mechanical characteristics of permafrost around the road, the thermal stability and the engineering characteristics of the pipeline are the key problems in the study of the buried pipeline project in the permafrost region. This paper takes the pipeline and the surrounding soil in a certain section of the pipeline and the surrounding soil in the permafrost region of the permafrost region of the Qinghai Tibet Plateau as the research object, aiming at the retreat of permafrost along the section. Combined with the characteristics of permafrost in this section, considering the future climate warming environmental factors and the basic theory of heat transfer, the large finite element numerical calculation software ANSYS is used for the buried depth of different pipeline centers, the temperature of the medium in different pipes, the insulation measures and the consideration of the soil around the pipeline under the condition of the phase change process of ice water. The distribution of the unsteady temperature field is numerically solved, and the temperature distribution trend of the soil around the pipe under different conditions is obtained. At the same time, the distribution of the internal equivalent stress of the pipeline under different conditions is calculated by using the ANSYS thermal indirect coupling method. The main conclusion of this paper is as follows: (1) through the high altitude under different conditions The numerical calculation of the soil temperature field around the buried positive temperature gas pipeline in permafrost region shows that the thermal stability of the permafrost in this section is poor, and the threat of the permafrost surrounding the permafrost around the pipeline is greatly threatened by the buried positive temperature pipeline. (2) the distribution of the temperature field around the permafrost around the pipeline center depth. In general, the deeper the buried depth of the pipe is, the greater the depth of the permafrost melting at the bottom of the pipe in the calculation time. When the buried depth of the pipe center is 2.0m, 2.5m, 3.0m, the pipeline bottom is calculated for fiftieth years under the conditions of the medium transport temperature of 10 and 16. The depth of permafrost melting in the Ministry is 2.76m, 3.21M, 3.68m and 2.84m, 3.35M, 3.76M. In the design of the positive temperature gas pipeline, the buried depth of the pipe center should be economical and reasonable. (3) the maximum melting thickness of the soil body below the bottom of the pipe is greater as the medium pipe inside the tube is transported. The pipe center buried depth 2.0m, in the pipe. The maximum melting thickness of the soil under the bottom of the pipeline is 43cm and 50cm under the conditions of the internal medium transport temperature of 10 and 16, and the maximum melting thickness of the soil below the bottom of the pipe is 38cm and 47cm under the buried depth of 2.5m in the pipe center, when the pipeline center is buried at the temperature of 10 and 16, and the medium is transported in the pipe center when the depth is 3.0m. Under the conditions of 10 C and 16 C, the maximum thicknesses of the soil under the bottom of the pipe are 35cm and 43cm, respectively. In the actual operation, the medium transport temperature should be controlled to avoid the high temperature in the tube, and (4) the use of 45mm thick polyurethane foam as the insulation of the outer wall of the pipeline can effectively reduce the heat of the positive temperature gas pipeline. When the thermal disturbance of permafrost around the pipe is measured, the melting range of permafrost around the pipe is less than that without heat preservation measures when there is heat preservation measures. The 45mm thick polyurethane foam is used as the insulation measure of the outer wall of the pipeline. When the pipeline center is buried deep for 2.0m, the medium bottom soil under the bottom of the pipe is under the condition of the medium transport temperature of 10 and 16. The maximum thicknesses of the body melt are 0mm and 43.7mm, and the maximum melting thickness of the soil below the bottom of the pipe is 0mm and 35.3mm under the condition of the medium transport temperature of 10 and 16 C in the pipe center, when the pipeline center is 10 and 16 C. The maximum melting of the soil below the bottom of the pipe under the buried depth of the pipeline is at the temperature of 10 and 16. The thickness is 0mm and 30.5mm, respectively. (5) during the first 10~20 years of buried positive temperature pipeline, the heat disturbance of the positive temperature pipeline is the greatest. During this period, the temperature monitoring and maintenance of the soil around the pipeline should be strengthened. (6) under different conditions, due to the internal pressure of the pipe, weight and overlying soil The maximum value of the equivalent stress generated by the weight and the change of the surrounding soil temperature is located inside the bottom of the pipe. (7) the equivalent stress at the bottom of the pipe gradually increases with the increase of the calculation time, and the maximum equivalent stress is thirtieth years in the calculation, and (8) the medium transport temperature in the pipe pipe. Under the condition of 16 degrees centigrade, the greater the depth of the pipe center is, the greater the buried depth of the pipe center, the greater the equivalent stress produced in the pipe due to the pressure inside the pipe, the weight of the self weight, the weight of the overlying soil and the load of the surrounding soil temperature. In the thirtieth year calculation, the equivalent stress at the bottom of the bottom of the pipe under the buried depth of 3.0m in the pipeline is 203MP. A, the buried depth of the pipe center is 2.5m, and the equivalent stress of 2.0m is 172MPa, 149MPa respectively, which is 1.36 times and 1.18 times the equivalent stress at the pipe center depth of 2.0m and 2.5m respectively. (9) the pipeline center buried depth is the same, the medium transport temperature in the pipe is 16 C, and the 45mm polyurethane foam can effectively reduce the pipe due to the pipeline. Internal pressure, self weight, weight of overlying soil mass and the equivalent stress produced by the load produced by the surrounding soil temperature change, the equivalent stress value at the bottom of the bottom of the pipe is 135MPa maximum when the pipe center is buried deep 3.0m, while the buried depth of the pipe center is 2.0m, and the equal effect force is 78.3MPa and 94.7MPa respectively, respectively, when 2.5m is no heat preservation. The equivalent stress of two pipes at the bottom of the pipeline is 52.6%, 55.1% and 58.7%. at the bottom of the pipeline.
【學(xué)位授予單位】：蘭州交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TE973

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