考虑湿陷的大厚度黄土地区桩基负摩阻力特性研究
发布时间：2018-08-18 09:26
【摘要】：桩基础作为一种重要的深基础形式,具有沉降量小和承载力高的优点,目前在大厚度黄土地区得到非常广泛的应用。工程实践证明桩的侧摩阻力在不同工况下取值会有很大的差异,为能深入研究桩与土体之间的相互作用,把握侧摩阻力取值的规律,本文通过现场试验、缩尺模型试验和数值模拟分析相结合的方法进行研究,对考虑湿陷的大厚度黄土地区桩基负摩阻力特性有了更全面和深入的认识,主要完成的工作和取得的成果如下： (1)借助实际工程,通过现场大型试验研究桩基在天然状态下及浸水条件下桩顶荷载与桩体沉降的关系；通过对黄土地区土体湿陷、沉降特点及不同深度土层的沉降变化特征的研究,分析了桩周土体沉降与桩身荷载传递规律之间的关系；分析了试桩在预浸水条件下桩身承载力和正负摩阻力的变化规律,并与未进行预浸水的试桩进行了对比分析,研究了桩身轴力分布和中性点位置变化以及桩身摩阻力的分布规律。 (2)以相似理论为基础,通过对国内外桩基负摩阻力的试验方案分析与研究,将原型桩和缩尺模型桩进行相似关系转化,自主设计了一套考虑湿陷的桩基负摩阻力的缩尺模型试验方案及方法,对大直径沉管灌注单桩承载力进行缩尺模型试验研究,并进行了负摩阻力试验,得到了桩的中性点位置以及负摩阻力产生和发展的规律。 (3)基于ADINA大型有限元分析软件对黄土地区单桩和群桩的负摩阻力进行了分析。主要研究内容包括：有限元模型的建立、浸水计算模型的设置、桩基P-S关系分析、桩顶加载工况下桩身轴力分析、浸水工况下桩周土体沉降分析、浸水工况下桩身轴力分析和浸水工况下桩侧负摩阻力分析。 (4)以西北黄土地区实际工程为背景,借助数值分析软件ADINA,建立了有限元分析模型,计算了桩顶加载及浸水工况下,桩身轴力及负摩阻力,并对影响桩身轴力及负摩阻力特性的参数进行了分析。主要研究了黄土弹性模量、黄土粘聚力、桩顶荷载、桩体刚度和浸水压力等对桩身轴力及负摩阻力的影响。
[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.
【学位授予单位】：兰州理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU473.1;TU444
本文编号：2189049
[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.
【学位授予单位】：兰州理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU473.1;TU444
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