【摘要】：隨著濱海地區(qū)經(jīng)濟(jì)的快速發(fā)展,土地資源日趨緊張,吹填造陸工程越來越多。新吹填場(chǎng)地的地質(zhì)條件具有淺層新吹填土欠固結(jié)、中深部海底沉積層軟弱的特征。因此,吹填場(chǎng)地中進(jìn)行基礎(chǔ)工程建設(shè),樁基礎(chǔ)受負(fù)摩擦力的影響顯著,且呈現(xiàn)淺層欠固結(jié)土自重固結(jié)和下臥層在堆載下壓縮沉降的綜合作用。對(duì)新吹填場(chǎng)地中的樁基受力特性開展研究,揭示綜合效應(yīng)下的樁基負(fù)摩擦力作用機(jī)理,評(píng)估其負(fù)摩擦力發(fā)生發(fā)展過程,并提出相應(yīng)的計(jì)算分析方法,可以為我國(guó)快速發(fā)展的填海造地區(qū)域的工程建設(shè)提供理論和技術(shù)支撐,不僅有很強(qiáng)的科學(xué)意義還有顯著的實(shí)用價(jià)值。本文結(jié)合實(shí)際工程,通過現(xiàn)場(chǎng)試驗(yàn)、數(shù)值模擬等方法研究了大面積吹填場(chǎng)地中樁基的受力變形特性,并總結(jié)出吹填場(chǎng)地中單樁負(fù)摩擦力受力模式和簡(jiǎn)化計(jì)算方法,取得了如下成果:(1)對(duì)大面積吹填場(chǎng)地中樁基受力特性進(jìn)行長(zhǎng)期原位測(cè)試,分析樁身負(fù)摩擦力的產(chǎn)生和發(fā)展規(guī)律。采用滑動(dòng)測(cè)微計(jì)對(duì)兩根試驗(yàn)樁的樁身應(yīng)變進(jìn)行長(zhǎng)期監(jiān)測(cè),從而得到樁身軸力分布特征和樁側(cè)摩阻力變化情況�，F(xiàn)場(chǎng)試驗(yàn)結(jié)果表明,新吹填場(chǎng)地中的樁基在施工完成后開始逐步受到負(fù)摩擦力作用,其樁身軸力和中性點(diǎn)深度隨時(shí)間不斷增大,沉樁完成1年后仍未穩(wěn)定。樁身淺部受到明顯的負(fù)摩擦力作用,其中吹填土層內(nèi)的負(fù)摩擦力隨深度的增加而增大,下臥原狀土層內(nèi)的負(fù)摩擦力隨深度減小。(2)考慮飽和土流固耦合的Biot固結(jié)理論,對(duì)吹填場(chǎng)地中樁基的長(zhǎng)期受力特性進(jìn)行數(shù)值模擬分析。根據(jù)試驗(yàn)樁的靜載荷試驗(yàn)結(jié)果進(jìn)行反分析,確定數(shù)值計(jì)算的土層參數(shù)參數(shù),并結(jié)合地質(zhì)勘察報(bào)告和試驗(yàn)樁現(xiàn)場(chǎng)試驗(yàn)結(jié)果進(jìn)行驗(yàn)證。應(yīng)用驗(yàn)證后的計(jì)算參數(shù)對(duì)兩根試驗(yàn)樁負(fù)摩擦力的長(zhǎng)期發(fā)展性狀進(jìn)行預(yù)測(cè)評(píng)估。計(jì)算結(jié)果表明,該吹填場(chǎng)地中樁基的軸力和中性點(diǎn)深度在沉樁3年以后可基本達(dá)到穩(wěn)定,穩(wěn)定狀態(tài)下的負(fù)摩擦力分布仍表現(xiàn)為:吹填土層內(nèi)隨深度增大、下臥原狀土層內(nèi)隨深度減小。(3)考慮樁基設(shè)計(jì)和使用的不同工況,應(yīng)用上述數(shù)值方法對(duì)吹填場(chǎng)地中樁基受力性狀進(jìn)行參數(shù)分析。針對(duì)樁頂受力和樁周堆載共同作用下的樁基工作狀態(tài),分析了堆載條件和樁長(zhǎng)對(duì)樁身負(fù)摩擦力的影響規(guī)律。針對(duì)吹填場(chǎng)地的特點(diǎn),通過參數(shù)分析研究了吹填土層厚度和負(fù)摩擦力消除措施對(duì)樁身受力的影響,并比較了吹填土層和地面堆載作用下樁基負(fù)摩擦力的差異,進(jìn)一步驗(yàn)證了吹填場(chǎng)地中負(fù)摩擦力發(fā)展和分布特點(diǎn)。(4)根據(jù)現(xiàn)場(chǎng)試驗(yàn)和數(shù)值分析結(jié)果,提出了吹填場(chǎng)地中單樁負(fù)摩擦力的簡(jiǎn)化計(jì)算方法。由測(cè)試和數(shù)值分析考慮到現(xiàn)行規(guī)范方法計(jì)算吹填土中樁基中性點(diǎn)和最大負(fù)摩擦力的結(jié)果偏差較大,根據(jù)原位測(cè)試和數(shù)值分析結(jié)果提出了簡(jiǎn)化的樁身負(fù)摩擦力分布模式——吹填土層內(nèi)負(fù)摩擦力隨深度增加而下臥土層內(nèi)隨深度減小,進(jìn)而推導(dǎo)出樁基中性點(diǎn)和軸力的計(jì)算公式。與規(guī)范方法計(jì)算結(jié)果、數(shù)值分析預(yù)測(cè)結(jié)果的比較分析表明,該方法可以簡(jiǎn)便而準(zhǔn)確的確定吹填場(chǎng)地內(nèi)樁身受力性狀,可為工程設(shè)計(jì)計(jì)算提供參考。
[Abstract]:With the rapid economic development in coastal areas, land resources are increasingly tense, and more and more land reclamation projects are carried out by dredger. The geological conditions of new dredger fill sites are characterized by underconsolidation of shallow new dredger fill and weak sedimentary layers in the middle and deep seabed. The comprehensive effect of self-weight consolidation of under-consolidated soil and compression settlement of underlying stratum under surcharge is studied. The mechanical characteristics of pile foundation in new dredger fill site are studied, the mechanism of negative friction of pile foundation under comprehensive effect is revealed, the occurrence and development process of negative friction is evaluated, and the corresponding calculation and analysis methods are put forward, which can be used for rapid development of filling in China. The theory and technology support provided by the engineering construction in the marine area is not only of great scientific significance but also of great practical value. Combining with the practical engineering, this paper studies the stress and deformation characteristics of the pile foundation in the large-area dredger fill site by means of field test and numerical simulation, and summarizes the stress mode of the negative friction of the single pile in the dredger fill site. The main results are as follows: (1) In-situ testing of pile foundation in large-area dredger filling site is carried out for a long time to analyze the generation and development of negative friction of pile body. Field test results show that the pile foundation in the new filling site is gradually subjected to negative friction after construction. The axial force and the depth of the neutral point of the pile increase with time, and the pile is still unstable one year after the completion of pile driving. The negative friction in the undisturbed soil layer decreases with the increase of the depth. (2) Considering the fluid-solid coupling theory of the saturated soil, the long-term mechanical behavior of the pile foundation in the dredger filling site is simulated and analyzed numerically. The results show that the axial force and the depth of the neutral point of the pile foundation in the dredger fill site can be basically stable after three years of piling, and the distribution of the negative friction force in the stable state can be basically stable. (3) Considering the different working conditions of pile foundation design and use, the above numerical method is used to analyze the behavior of pile foundation in the dredger fill site. According to the working state of pile foundation under the combined action of pile top force and pile surcharge, the condition of surcharge is analyzed. According to the characteristics of dredger fill site, the influence of dredger fill thickness and negative friction eliminating measures on pile body force is analyzed and studied by parameter analysis, and the difference of negative friction between dredger fill and ground surcharge is compared, which further verifies the development of negative friction in dredger fill site. (4) Based on the field test and numerical analysis results, a simplified method for calculating the negative friction force of a single pile in a dredged fill site is proposed. Considering the large deviation between the results of calculation of the neutral point and the maximum negative friction force of the pile foundation in the dredged fill soil by the test and numerical analysis, a new method is proposed according to the results of in-situ test and numerical analysis. A simplified distribution model of negative friction of pile body-the negative friction in dredged fill decreases with the increase of depth in the underlying soil layer, and then the calculation formulas of the neutral point and axial force of pile foundation are deduced. The behavior of the internal pile can provide reference for engineering design calculation.
【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU473.1

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