本文選題：宏細(xì)觀多尺度 + 沉井下沉　； 參考：《東南大學(xué)》2015年碩士論文

【摘要】：隨著計(jì)算機(jī)技術(shù)的發(fā)展,大量學(xué)者開始采用數(shù)值分析法對(duì)巖土工程問題進(jìn)行模擬分析,并取得了大量成果。巖土工程中廣泛采用有限差分法和離散元法兩種數(shù)值分析方法,但兩者都存在各自的缺點(diǎn)。國(guó)內(nèi)外學(xué)者提出了通過兩種方法耦合分析來彌補(bǔ)兩種方法的缺點(diǎn)的設(shè)想,從此,離散-連續(xù)耦合分析方法成為了目前國(guó)內(nèi)外學(xué)者的研究熱點(diǎn)。本文提出了三維離散元-有限差分法耦合分析方法,并完成pFC3D和FLAC3D耦合計(jì)算程序。采用其計(jì)算程序?qū)Τ辆鲁吝^程、沉樁過程、沉箱-墊層-樁復(fù)合基礎(chǔ)加載過程進(jìn)了宏細(xì)觀多尺度耦合分析,主要的研究工作及結(jié)論如下：(1)提出了離散元-有限差分法耦合算法,通過模擬壓縮試驗(yàn)、直剪試驗(yàn)、三軸試驗(yàn)三種室內(nèi)試驗(yàn),證明本文所提出的離散元-有限差分法耦合計(jì)算方法能夠使耦合界面法向力和切向力準(zhǔn)確地傳遞,并且保證在顆粒與差分網(wǎng)格的宏細(xì)觀參數(shù)相互匹配的情況下,離散元和有限差分網(wǎng)格耦合建模能夠保證本構(gòu)關(guān)系相同,兩者之間變形協(xié)調(diào)。(2)對(duì)沉井下沉過程進(jìn)行數(shù)值模擬,探究沉井下沉過程機(jī)理。數(shù)值模擬結(jié)果表明,沉井下沉過程中,沉井側(cè)壁土壓力分布曲線有明顯的拐點(diǎn),在刃腳附近出現(xiàn)應(yīng)力松弛區(qū)域,致使沉井側(cè)壁土壓力減小并逐漸趨于主動(dòng)土壓力,在刃腳附近側(cè)壁土壓力甚至小于主動(dòng)土壓力；采用“土拱效應(yīng)”理論,對(duì)沉井側(cè)壁土壓力進(jìn)行計(jì)算,計(jì)算結(jié)果更加接近實(shí)際情況。(3)對(duì)沉樁過程進(jìn)行數(shù)值模擬,探究沉樁過程機(jī)理。數(shù)值模擬結(jié)果表明,沉樁尺寸對(duì)沉樁擠土效應(yīng)影響很大,樁周土體位移隨著樁徑的增大而增大,且樁周土體位移沿遠(yuǎn)離樁軸方向迅速衰減；振動(dòng)沉樁可以有效的減小樁體在沉樁過程中樁側(cè)摩阻力以及樁端阻力,但并不是沉樁振動(dòng)頻率越高越好,其振動(dòng)頻率應(yīng)該根據(jù)土體性質(zhì)進(jìn)行調(diào)整,以達(dá)到最佳振動(dòng)頻率。(4)對(duì)沉箱-墊層-樁復(fù)合基礎(chǔ)加載過程進(jìn)行數(shù)值模擬,分析了墊層厚度對(duì)沉箱-墊層-樁復(fù)合基礎(chǔ)受力特性的影響。數(shù)值模擬結(jié)果表明,墊層厚度越大,基礎(chǔ)沉降越大,樁頂刺入量越大,土體荷載分擔(dān)比越高；在加載過程中,隨著荷載的增大,土體荷載分擔(dān)比逐漸下降,樁荷載分擔(dān)比逐漸升高；其他條件相同情況下,樁頂刺入墊層程度與樁位置有關(guān),內(nèi)部基樁刺入量小,外部基樁刺入量相對(duì)較大。通過對(duì)三種基礎(chǔ)形式的離散元-有限差分法耦合計(jì)算分析,較好地從宏細(xì)觀多尺度分析了三種基礎(chǔ)在建造或加載等過程的特性,驗(yàn)證了本文提出的離散元-有限差分法耦合計(jì)算的實(shí)用性。
[Abstract]:With the development of computer technology, a large number of scholars began to use numerical analysis method to simulate and analyze geotechnical engineering problems, and achieved a lot of results. Finite difference method and discrete element method are widely used in geotechnical engineering, but both have their own shortcomings. Scholars at home and abroad have put forward the idea of two methods coupling analysis to make up for the shortcomings of the two methods. Since then, the discrete-time continuous coupling analysis method has become the research hotspot of scholars at home and abroad. In this paper, the coupling analysis method of 3D discrete element-finite-difference method is presented, and the pFC3D and FLAC3D coupling calculation program is completed. The process of sinking, piling and loading of caisson cushion pile composite foundation are analyzed by using its calculation program. The main research work and conclusions are as follows: (1) the discrete element finite difference method (DFDM) coupling algorithm is proposed. The three indoor tests are simulated compression test, direct shear test and triaxial test. It is proved that the discrete element finite difference method presented in this paper can accurately transfer the normal and tangential forces at the coupled interface, and ensure that the particles and the meso-macro parameters of the difference mesh can match each other. The coupling modeling of discrete element and finite difference grid can guarantee the same constitutive relation. The deformation coordination between them can be used to simulate the sinking process of caisson and to explore the mechanism of sinking process of caisson. The numerical simulation results show that there is an obvious inflection point in the lateral wall earth pressure distribution curve of the caisson during the sinking process, and the stress relaxation area appears near the edge of the caisson, which results in the decrease of the side wall earth pressure of the caisson and gradually tends to the active earth pressure. The soil pressure of side wall near the edge foot is even smaller than that of active earth pressure, and the "soil arch effect" theory is used to calculate the lateral wall earth pressure of caisson, and the calculated results are closer to the actual situation. Explore the mechanism of piling process. The numerical simulation results show that the piling size has a great influence on the pile-squeezing effect, the soil displacement around the pile increases with the increase of the pile diameter, and the soil displacement around the pile decays rapidly along the direction away from the pile axis. Vibration piling can effectively reduce the pile side friction and pile tip resistance in the process of piling, but it is not that the higher the vibration frequency, the better, the vibration frequency should be adjusted according to the soil properties. The loading process of caisson-cushion-pile composite foundation is numerically simulated to reach the optimum vibration frequency. The influence of cushion thickness on the mechanical characteristics of caisson-cushion-pile composite foundation is analyzed. The numerical simulation results show that the greater the cushion thickness, the greater the foundation settlement, the greater the pile top impinging, the higher the load-sharing ratio of soil, and the lower the load-sharing ratio of soil is during the loading process with the increase of load. Under the same conditions, the degree of pile top penetration into the cushion is related to the pile position, the internal pile penetration is small, and the external pile penetration is relatively large. By means of the coupled calculation and analysis of three basic forms of discrete element and finite difference method, the characteristics of the three foundations in the process of construction or loading are well analyzed from the macro and mesoscale view. The practicability of the discrete-time finite-difference method proposed in this paper is verified.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU473

【相似文獻(xiàn)】

相關(guān)期刊論文 前5條

1 邱澤華,張寶紅;用力矩模型解釋摩擦試驗(yàn)加載過程中的非線性變化[J];巖石力學(xué)與工程學(xué)報(bào);2004年02期

2 施漢仁;沈高;孫力彤;;高層建筑結(jié)構(gòu)施工加載過程對(duì)內(nèi)力計(jì)算的影響[J];山西建筑;2006年17期

3 孫世永;;考慮加載過程砂井地基平面應(yīng)變等效方法研究[J];路基工程;2010年05期

4 鄭貴平;趙興東;劉建坡;李元輝;;巖石加載過程聲波波速變化規(guī)律實(shí)驗(yàn)研究[J];東北大學(xué)學(xué)報(bào)(自然科學(xué)版);2009年08期

5 ;[J];;年期

相關(guān)會(huì)議論文 前1條

1 李紀(jì)漢;劉曉紅;方亞如;郝晉升;耿乃光;;巖石加載過程中聲發(fā)射效應(yīng)的各向異性[A];第五屆全國(guó)構(gòu)造物理、第三屆全國(guó)高溫高壓學(xué)術(shù)討論會(huì)論文摘要[C];1992年

相關(guān)碩士學(xué)位論文 前2條

1 徐健;基于多尺度研究方法的深基礎(chǔ)建造及加載過程特性分析[D];東南大學(xué);2015年

2 嚴(yán)向峰;激光加載過程中金屬熔化的數(shù)值計(jì)算[D];沈陽航空航天大學(xué);2013年

，

本文編號(hào)：1962936