【摘要】：樁基礎(chǔ)作為一種重要的深基礎(chǔ)形式,具有沉降量小和承載力高的優(yōu)點(diǎn),目前在大厚度黃土地區(qū)得到非常廣泛的應(yīng)用。工程實(shí)踐證明樁的側(cè)摩阻力在不同工況下取值會(huì)有很大的差異,為能深入研究樁與土體之間的相互作用,把握側(cè)摩阻力取值的規(guī)律,本文通過(guò)現(xiàn)場(chǎng)試驗(yàn)、縮尺模型試驗(yàn)和數(shù)值模擬分析相結(jié)合的方法進(jìn)行研究,對(duì)考慮濕陷的大厚度黃土地區(qū)樁基負(fù)摩阻力特性有了更全面和深入的認(rèn)識(shí),主要完成的工作和取得的成果如下： (1)借助實(shí)際工程,通過(guò)現(xiàn)場(chǎng)大型試驗(yàn)研究樁基在天然狀態(tài)下及浸水條件下樁頂荷載與樁體沉降的關(guān)系；通過(guò)對(duì)黃土地區(qū)土體濕陷、沉降特點(diǎn)及不同深度土層的沉降變化特征的研究,分析了樁周土體沉降與樁身荷載傳遞規(guī)律之間的關(guān)系；分析了試樁在預(yù)浸水條件下樁身承載力和正負(fù)摩阻力的變化規(guī)律,并與未進(jìn)行預(yù)浸水的試樁進(jìn)行了對(duì)比分析,研究了樁身軸力分布和中性點(diǎn)位置變化以及樁身摩阻力的分布規(guī)律。 (2)以相似理論為基礎(chǔ),通過(guò)對(duì)國(guó)內(nèi)外樁基負(fù)摩阻力的試驗(yàn)方案分析與研究,將原型樁和縮尺模型樁進(jìn)行相似關(guān)系轉(zhuǎn)化,自主設(shè)計(jì)了一套考慮濕陷的樁基負(fù)摩阻力的縮尺模型試驗(yàn)方案及方法,對(duì)大直徑沉管灌注單樁承載力進(jìn)行縮尺模型試驗(yàn)研究,并進(jìn)行了負(fù)摩阻力試驗(yàn),得到了樁的中性點(diǎn)位置以及負(fù)摩阻力產(chǎn)生和發(fā)展的規(guī)律。 (3)基于ADINA大型有限元分析軟件對(duì)黃土地區(qū)單樁和群樁的負(fù)摩阻力進(jìn)行了分析。主要研究?jī)?nèi)容包括：有限元模型的建立、浸水計(jì)算模型的設(shè)置、樁基P-S關(guān)系分析、樁頂加載工況下樁身軸力分析、浸水工況下樁周土體沉降分析、浸水工況下樁身軸力分析和浸水工況下樁側(cè)負(fù)摩阻力分析。 (4)以西北黃土地區(qū)實(shí)際工程為背景,借助數(shù)值分析軟件ADINA,建立了有限元分析模型,計(jì)算了樁頂加載及浸水工況下,樁身軸力及負(fù)摩阻力,并對(duì)影響樁身軸力及負(fù)摩阻力特性的參數(shù)進(jìn)行了分析。主要研究了黃土彈性模量、黃土粘聚力、樁頂荷載、樁體剛度和浸水壓力等對(duì)樁身軸力及負(fù)摩阻力的影響。
[Abstract]:As an important form of deep foundation, pile foundation has the advantages of small settlement and high bearing capacity, and is widely used in loess regions with large thickness. Engineering practice has proved that the value of side friction of pile will be very different under different working conditions. In order to study the interaction between pile and soil and grasp the law of side friction, this paper passes the field test. The method of scale model test and numerical simulation is used to study the characteristics of negative friction resistance of pile foundation in loess region with large thickness considering collapsibility. The main works and achievements are as follows: (1) with the aid of practical engineering, the relationship between pile top load and pile settlement under natural condition and flooding condition is studied by large-scale field test; The relationship between the settlement of soil around piles and the law of load transfer of piles is analyzed by studying the characteristics of soil subsidence and settlement in loess area and the characteristics of settlement of soil layers at different depths. The variation law of bearing capacity and positive and negative frictional resistance of test pile under pre-immersion condition is analyzed and compared with that of test pile without pre-immersion. The distribution of axial force and neutral point and the distribution of frictional resistance of pile body are studied. (2) based on the similarity theory, the negative friction of pile foundation at home and abroad is analyzed and studied. By transforming the similarity between the prototype pile and the scale model pile, a scale model test scheme and method considering the negative frictional resistance of the collapsing pile foundation are designed, and the bearing capacity of the large diameter sinking pipe cast-in-place single pile is studied by the scale model test. The negative frictional resistance test is carried out, and the neutral position of pile and the rule of the generation and development of negative friction resistance are obtained. (3) the negative friction resistance of single pile and pile group in loess area is analyzed based on ADINA large-scale finite element analysis software. The main research contents include: the establishment of finite element model, the setting of soaking calculation model, the analysis of P-S relation of pile foundation, the analysis of axial force of pile body under pile top loading, and the settlement analysis of soil around pile under flooding condition. The axial force analysis of pile body under flooding condition and the negative friction analysis of pile side under flooding condition. (4) based on the actual engineering in Northwest Loess region, the finite element analysis model is established with the aid of the numerical analysis software ADINA. The axial force and negative frictional resistance of the pile are calculated under the loading and flooding conditions of the pile top, and the parameters affecting the axial force and the negative friction resistance of the pile are analyzed. The effects of elastic modulus of loess, cohesive force of loess, load on pile top, stiffness of pile body and immersion pressure on axial force and negative friction of pile body are studied.
【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU473.1;TU444

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