【摘要】：吸力式筒形基礎(chǔ)在海洋工程中已獲得越來越廣泛的應(yīng)用,其安裝過程的數(shù)值模擬及理論研究對(duì)指導(dǎo)工程實(shí)踐具有重要意義。在大型通用有限元軟件ABAQUS平臺(tái)上建立了二維軸對(duì)稱模型,基于任意拉格朗日-歐拉算法(Arbitrary Lagrangian-Eulerian formulation, ALE)技術(shù),解決了大變形網(wǎng)格畸變問題,成功模擬了黏性土中吸力筒的沉貫過程。在數(shù)值模型中通過編寫子程序VUFIELD表達(dá)土體的不排水抗剪強(qiáng)度和彈性模量隨土體深度變化。采用西澳大學(xué)的離心機(jī)試驗(yàn)數(shù)據(jù)及理論計(jì)算,對(duì)模型進(jìn)行驗(yàn)證。利用已驗(yàn)證數(shù)值模型分析了不同吸力下沉貫阻力、土塞高度并討論了筒壁摩擦特性對(duì)吸力筒沉貫的影響。數(shù)值計(jì)算結(jié)果表明,ALE技術(shù)能有效模擬吸力筒貫入過程,很好地解決了由于土體大變形而引起的網(wǎng)格畸變問題。貫入方式對(duì)貫入阻力影響很大,吸力式貫入阻力明顯低于壓力式貫入阻力。進(jìn)一步研究發(fā)現(xiàn),隨著最終吸力值的增大,沉貫阻力會(huì)顯著降低,土塞高度會(huì)顯著提高。對(duì)吸力筒內(nèi)壁摩擦特性的研究表明,內(nèi)壁摩擦阻力是導(dǎo)致沉貫阻力改變的主要因素；相比吸力式貫入方式,壓力式貫入受筒壁摩擦特性的影響更為顯著。通過理論推導(dǎo)建立了吸力筒內(nèi)壁摩擦力解析模型,并對(duì)沉貫過程中滲流作用對(duì)筒內(nèi)壁摩擦阻力的影響進(jìn)行了研究。從筒內(nèi)土體微元段受力平衡的角度出發(fā),充分考慮土體受力和變形狀態(tài)以及滲流作用,推導(dǎo)了吸力筒貫入過程中土-筒摩擦應(yīng)力計(jì)算的解析模型。并通過有限元程序ABAQUS建立吸力筒沉貫及土體滲流數(shù)值模型,對(duì)解析模型進(jìn)行對(duì)比和驗(yàn)證。針對(duì)滲流速度、土-筒摩擦系數(shù)和筒體長(zhǎng)徑比進(jìn)行了討論分析。結(jié)果表明,滲流作用會(huì)顯著降低土體的豎直有效應(yīng)力,從而減小筒內(nèi)壁摩擦阻力。通過對(duì)滲流速度的分析,發(fā)現(xiàn)應(yīng)根據(jù)滲流速度判斷滲流體系,從而合理選取不同滲流理論獲得準(zhǔn)確的筒內(nèi)壁摩擦力結(jié)果。土-筒摩擦系數(shù)增大會(huì)造成土-筒法向正應(yīng)力的增大,進(jìn)而使得摩擦應(yīng)力進(jìn)一步增大。增大筒體長(zhǎng)徑比會(huì)增加土-筒摩擦應(yīng)力,但筒內(nèi)壁總摩擦力會(huì)隨著筒長(zhǎng)徑比呈現(xiàn)倒拋物線的變化形式,存在最小值。由于理論推導(dǎo)是建立在筒內(nèi)土體豎直有效應(yīng)力沿徑向均勻分布的假設(shè)基礎(chǔ)上的,因而在使用該解析模型時(shí),應(yīng)考慮筒體長(zhǎng)徑比滿足一定的限定條件。由于海洋工程問題的復(fù)雜性,以及試驗(yàn)研究的高成本和不確定性,通過本研究可以看出,數(shù)值模擬仍然是對(duì)海洋工程及其基礎(chǔ)構(gòu)筑物研究的有效方法。大變形有限元模擬技術(shù)對(duì)吸力筒的研究取得了一定的成功,但應(yīng)得到進(jìn)一步的改進(jìn),比如對(duì)于特殊土體采用合適的本構(gòu)模型；提高ALE數(shù)值計(jì)算的速度等。數(shù)值模擬對(duì)吸力筒的研究還應(yīng)進(jìn)一步考慮土體微細(xì)觀和特細(xì)觀特性等。
[Abstract]:Suction cylindrical foundation has been more and more widely used in marine engineering. Numerical simulation and theoretical study of its installation process are of great significance to guide engineering practice. Based on the Arbitrary Lagrangian-Eulerian formation (ale) technique, a two-dimensional axisymmetric model is established on the platform of Abaqus. The problem of large deformation mesh distortion is solved, and the sinking process of suction cylinder in clay is successfully simulated. In the numerical model, the undrained shear strength and elastic modulus of soil are expressed by the subprogram VUFIELD with the variation of soil depth. The model is verified by the centrifuge test data and theoretical calculation of the University of Western Australia. By using the verified numerical model, the penetration resistance of different suction sinking forces and the height of soil plug are analyzed and the influence of friction characteristics of cylinder wall on the penetration of suction cylinder is discussed. The numerical results show that ale technique can effectively simulate the penetration process of suction cylinder and solve the problem of grid distortion caused by large deformation of soil. The penetration resistance of suction type is obviously lower than that of pressure type. It is found that with the increase of the ultimate suction value, the penetration resistance decreases significantly and the plug height increases significantly. The study of friction characteristics of suction cylinder shows that the friction resistance of inner wall is the main factor leading to the change of sinking resistance, and the pressure penetration is more significantly affected by the friction characteristics of cylinder than the suction penetration. Based on the theoretical derivation, an analytical model of friction force on the inner wall of suction cylinder is established, and the influence of seepage on friction resistance of inner wall of suction cylinder is studied. From the point of view of the stress balance of the micro-element section of the soil in the tube, the stress and deformation state of the soil and the seepage flow are fully considered, and an analytical model for the calculation of the soil-tube friction stress in the process of suction cylinder penetration is derived. The numerical models of suction tube penetration and soil seepage are established by finite element program Abaqus, and the analytical model is compared and verified. The seepage velocity, the friction coefficient of soil-cylinder and the ratio of length to diameter are discussed and analyzed. The results show that the vertical effective stress of soil can be significantly reduced by seepage and thus the friction resistance of the inner wall of the cylinder will be reduced. Through the analysis of the seepage velocity, it is found that the seepage system should be judged according to the seepage velocity, and the accurate friction results of the inner wall of the cylinder can be obtained by reasonably selecting different seepage theories. The increase of the friction coefficient of soil-tube will cause the normal stress of soil-cylinder to increase, and further increase the frictional stress. Increasing the ratio of length to diameter of the tube increases the friction stress, but the total friction force of the inner wall of the cylinder changes in the form of inverted parabola with the ratio of length to diameter of the tube, and there is a minimum value. Since the theoretical derivation is based on the assumption that the vertical effective stress is uniformly distributed along the radial direction of the soil in the tube, the length to diameter ratio of the cylinder should be taken into account when the analytical model is used. Due to the complexity of ocean engineering problems and the high cost and uncertainty of experimental research, it can be seen from this study that numerical simulation is still an effective method for the study of ocean engineering and its infrastructure. The finite element simulation technique of large deformation has achieved some success in the study of suction cylinder, but it should be further improved, such as adopting appropriate constitutive model for special soil mass, increasing the speed of ale numerical calculation, and so on. The study of suction cylinder by numerical simulation should further consider the microcosmic and special mesoscopic characteristics of soil.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU476;P75

【參考文獻(xiàn)】

相關(guān)期刊論文 前3條

1 朱儒弟,高恒慶,馬小兵,何生厚,王運(yùn)安,洪學(xué)福;海上平臺(tái)桶形基礎(chǔ)模型壓力壓貫與負(fù)壓沉貫試驗(yàn)研究[J];海岸工程;1999年01期

2 丁紅巖,劉振勇,陳星;吸力錨土塞在粉質(zhì)粘土中形成的模型試驗(yàn)研究[J];巖土工程學(xué)報(bào);2001年04期

3 金書成;張永濤;楊炎華;黎冰;;飽和砂土地基中吸力式桶形基礎(chǔ)水平承載力研究[J];巖土力學(xué);2013年S1期

相關(guān)會(huì)議論文 前1條

1 童景盛;王勝利;敖運(yùn)安;;側(cè)壓力系數(shù)研究與實(shí)踐[A];第21屆全國(guó)結(jié)構(gòu)工程學(xué)術(shù)會(huì)議論文集第Ⅰ冊(cè)[C];2012年

，

本文編號(hào)：2130114