本文關(guān)鍵詞：楔形勁芯水泥土復(fù)合樁成樁特性研究　出處：《湖南工業(yè)大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 水泥土抗壓強(qiáng)度 勁芯復(fù)合樁 成樁特性 貫入力 樁身應(yīng)變 PFC2D數(shù)值分析 模型試驗(yàn)

【摘要】：基于對(duì)混凝土勁芯樁、楔形樁的分析與總結(jié),課題組提出了一種軟土地基加固新技術(shù)——楔形勁芯水泥土復(fù)合樁。本文采用室內(nèi)土工試驗(yàn)、大尺寸模型試驗(yàn)與數(shù)值模擬相結(jié)合的方法,較為系統(tǒng)的研究楔形勁芯水泥土復(fù)合樁成樁特性,分析水泥土表面位移、內(nèi)芯和水泥土外樁樁身應(yīng)變以及壓樁貫入力等的變化規(guī)律,主要研究工作與成果包括:1、進(jìn)行室內(nèi)抗壓強(qiáng)度試驗(yàn),研究夯實(shí)水泥土無側(cè)限抗壓強(qiáng)度的發(fā)展規(guī)律。結(jié)果表明:夯實(shí)水泥土強(qiáng)度隨著齡期、摻入比的增加而增加,并通過回歸分析得出三者間的數(shù)量關(guān)系;夯實(shí)水泥土軸向應(yīng)力隨應(yīng)變先增大后減小,軸向峰值應(yīng)力隨摻入比、齡期的增加而增加;同時(shí),摻入比、齡期影響和改變水泥土的破壞方式。當(dāng)水泥用量偏低時(shí),早期水泥土強(qiáng)度較低,發(fā)生塑性破壞,隨著摻入比、養(yǎng)護(hù)齡期的增加,破壞方式慢慢轉(zhuǎn)變成脆性破壞。2、基于相似理論,設(shè)計(jì)模型試驗(yàn),研究楔形勁芯水泥土復(fù)合樁成樁特性。研究表明:1)貫入力受樁型、楔角和置換率等因素的影響。其他條件相同時(shí),貫入力隨水泥土含水率的增大而減小,隨內(nèi)芯置換率、楔角和平均直徑的增大而增大,同等條件下壓入楔形內(nèi)芯所需的貫入力比等截面內(nèi)芯的較大;2)等截面內(nèi)芯壓入時(shí),水泥土樁表面會(huì)出現(xiàn)“隆起”,內(nèi)芯直徑與置換率越大,“隆起”現(xiàn)象越明顯,且最大地表隆起量出現(xiàn)在1d~2d范圍內(nèi),約為樁徑的1%~1.5%;楔形內(nèi)芯壓入時(shí),水泥土樁表位移不斷增加,且增加的幅度隨楔角、置換率和水泥土含水率的增加而增大;3)水泥土樁樁底壓力、內(nèi)芯樁端壓力均隨內(nèi)芯豎向位移的增加而增加,與置換率、水泥土含水率和樁型有關(guān);4)水泥土樁身應(yīng)變隨深度的增加而先增大后減小,在某一樁深處出現(xiàn)峰值,且峰值應(yīng)變不斷增加;對(duì)于等截面內(nèi)芯,出現(xiàn)峰值應(yīng)變的深度隨內(nèi)芯的沉入而不斷下移,且始終在距離內(nèi)芯樁端約10cm以內(nèi)范圍;對(duì)比楔形和等截面內(nèi)芯,相同條件下壓入楔形內(nèi)芯時(shí)出現(xiàn)的應(yīng)變較大。3、基于模型試驗(yàn)結(jié)果,采用PFC2D軟件進(jìn)行數(shù)值分析,討論置換率和內(nèi)芯樁型對(duì)成樁特性的影響。分析表明:內(nèi)芯壓入使水泥土發(fā)生側(cè)向變形,置換率相同時(shí)內(nèi)芯直徑(或平均直徑)越大,側(cè)向變形量越大,且與等截面內(nèi)芯相比,楔形內(nèi)芯使水泥土產(chǎn)生的側(cè)向變形更大,成樁效果更顯著;內(nèi)芯所受阻力由樁端阻力和樁側(cè)阻力組成,二者在成樁過程中均隨內(nèi)芯豎向位移的增加而增加;楔形內(nèi)芯壓入過程中樁側(cè)阻力所占比例(約為80%~95%)遠(yuǎn)大于樁端阻力。
[Abstract]:Based on the analysis and summary of the concrete core pile and wedge-shaped pile, a new technology of strengthening soft soil foundation, wedge-shaped cement-soil composite pile, is put forward in this paper. In this paper, the laboratory geotechnical test is carried out. Based on the method of large-scale model test and numerical simulation, the characteristics of cement-soil composite pile with wedge-shaped rigid core are studied systematically, and the surface displacement of cement-soil is analyzed. The internal core and cement soil outside pile body strain and pressure pile penetration law, the main research work and results include: 1, the indoor compressive strength test. The development rule of unconfined compressive strength of rammed cement-soil is studied. The results show that the strength of compacted cement-soil increases with the increase of age and ratio, and the quantitative relationship among them is obtained by regression analysis. The axial stress of compacted cement-soil increases first and then decreases with strain, and the axial peak stress increases with the ratio of cement to soil and the age of the compacted cement-soil. At the same time, mixing ratio, age influence and change the failure mode of cement-soil. When the cement content is low, the strength of early cement-soil is lower, plastic failure occurs, and the curing age increases with the ratio of cement to soil. The failure mode slowly changed to brittle failure. Based on the similarity theory, the model test was designed to study the pile-forming characteristics of wedge-shaped cement-soil composite pile with strong core. The research shows that the penetration force is subjected to pile type. When the other conditions are the same, the penetration force decreases with the increase of water content of cement soil, and increases with the increase of core replacement ratio, wedge angle and mean diameter. Under the same conditions, the penetration force required to press the wedge core is larger than that of the equal section core. 2) when the inner core of the same section is pressed, the surface of the cement soil pile will appear "uplift". The larger the diameter of the core and the replacement rate, the more obvious the "uplift" phenomenon is, and the maximum surface uplift amount appears in the range of 1 d ~ 2 d. About 1 / 1. 5 of the diameter of the pile; The displacement of cement soil pile surface increases with the increase of wedge angle, replacement ratio and moisture content of cement soil. 3) the pressure on the bottom of cement-soil pile and the pressure at the end of the core pile increase with the increase of the vertical displacement of the core, which is related to the replacement rate, the moisture content of the cement soil and the pile type. 4) the strain of cement-soil pile firstly increases and then decreases with the increase of depth, and the peak value appears in a certain pile, and the peak strain increases constantly. For the inner core of the constant section, the depth of peak strain is continuously moving down with the inner core sinking, and always within 10 cm from the end of the inner core pile. Compared with the wedge core and the equal section inner core, under the same conditions, the strain in the wedge core is larger. 3. Based on the model test results, the numerical analysis is carried out by PFC2D software. The influence of displacement rate and core pile type on pile forming characteristics is discussed. The results show that the lateral deformation of cement-soil is caused by internal core indentation. The larger the core diameter (or average diameter) is when the replacement rate is the same, the larger the lateral deformation is. Compared with the inner core of the same section, the wedge-shaped core makes the lateral deformation of the cement soil larger, and the piling effect is more remarkable. The resistance of inner core is composed of pile tip resistance and pile side resistance, both of which increase with the increase of vertical displacement of inner core in the process of pile formation. The proportion of pile side resistance (about 80 / 95) is much larger than that of pile tip.
【學(xué)位授予單位】：湖南工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU473.1

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