【作者】 吕凡任；

【导师】 陈云敏；

【作者基本信息】 浙江大学 ， 岩土工程， 2004， 博士

【摘要】 斜桩以及有斜桩群桩广泛应用于桥梁、码头以及大型输电线路基础等。同时，由于施工机具、施工技术的限制，地质条件的变化，有的直桩也因施工原因成为斜桩。目前对于斜桩单桩和有斜桩群桩承载特性的研究，还鲜有文献报道。本文将斜桩单桩和有斜桩群桩作为研究对象，提出了“广义弹性理论法”进行分析，并结合大型输电线路杆塔基础微型桩技术开发，开展了模型试验、原型试验和工程应用研究。 在弹性理论法的基础上，假设桩-土之间存在相对位移，桩-土相互作用力是相对位移的函数，以模拟桩-土之间的相对位移和塑性作用，本文称为“广义弹性理论法”。这种方法可以考虑桩周土的塑性和桩-桩相互作用，还可以分析斜桩以及有斜桩的群桩。 把广义弹性理论法用于单桩分析，建立了相应的模型和公式。对于直桩，退化为弹性理论的计算结果同Poulos的结果一致，退化为荷载传递法与他人的结果基本吻合；然后研究了斜桩的荷载-变形特性，把公式用于计算Meyerhof的模型试验以及ZhangLM的离心机试验的荷载-位移关系，发现同试验结果吻合较好。结合前人的研究成果，根据不同模型的计算比较，确定了“广义弹性理论法”模型参数的取值方法。算例表明，竖向受荷直桩比斜桩有更大承载力；水平受荷单桩，“正斜”斜桩有较大的承载力，“负斜”斜桩承载力较小，直桩居中。就桩顶的竖向沉降而言，桩身的微小偏斜(小于10°)，对竖向受荷桩的正常使用没有明显的影响；倾角太大的斜桩承受竖向荷载的能力有所减少；直桩可以承受一定倾角(小于10°)的倾斜荷载，这时的倾斜荷载对桩顶的沉降影响较小，但桩顶水平位移增加比较明显。 把“广义弹性理论法”用于群桩分析，利用本文方法可以考虑桩-土以及桩-桩相互作用的优点，视单桩为轴向刚度、径向刚度和转动刚度己知的柱梁，建立了斜桩群桩分析模型，推导了相应的计算公式，其中单桩刚度采用迭代的方法计算。算例分析表明，随着群桩承受荷载的增加，单桩的轴力和刚度分布逐渐趋于均匀；比较单桩不同布置形式的群桩，发现圆形布置时其单桩轴力更加均匀。与单桩类似，竖向受荷直桩群桩承载力比斜桩群桩大；水平受荷群桩，“正斜”单桩组成的群桩比直桩群桩和“负斜”单桩组成的群桩的承载力大。 为了检验计算理论的合理性并指导工程设计和施工，分别在室内做了模型试验、在现场做了原型试验。模型试验发现，伸向四周的单桩组成的群桩具有更好的抵抗倾斜荷载的能力，这一点特别有利于输电线路基础等；原型试验发现，微型桩单桩和群桩的承载力完全达到设计承载要求，其群桩效率在0.9左右。根据原型试验和模型试验的地质条件，分别选择计算参数，计算荷载一变形曲线，同试验结果取得了比较好的一致，进一步说明计算理论和计算方法的合理性和可靠性。更多还原

【Abstract】 Battered pile and pile group are generally used in bridge, wharf and foundation of transmission power. As the limitation of equipment and technology of construction, some vertical piles are constructed to battered piles. There is less research about bartered pile and pile group. In this paper the "generalized elastic theory" is proposed to solve the problem. A series of model experiments and prototype experiments are run to explore the technology of transmission power foundation.Based on the elastic theory, the stress between the pile and the soil is assumed to be a function of the relative displacement. The model is called "generalized elastic theory" in this paper, which can take the plastic behavior of the soil around the pile into account, and also can analyze the battered pile and pile group.First, the generalized elastic theory is employed into in single pile analysis. The degeneration solution is accordant with Poulos’ results. Analyzing the load-displacement behavior of the battered pile, the results agree well with Meyerhof’s model experiments and ZhangLM’s centrifuge experiments. Then the author gives the method to determine the parameters of the generalized elastic theory. Computing examples show that the bearing capacity of the piles depend on the load inclination and the pile battered angle. Under the vertical load, the vertical pile has bigger bearing capacity than the battered pile. Under the lateral load, the positive battered pile has bigger bearing capacity than the vertical and the negative pile. The allowable settlement of the pile head is suggested and the vertical pile can bear load with inclination of less than 10 , and the battered pile bearing vertical load can be angle of less than 10 .Then the paper employed the generalized elastic theory in pile group, considering the interaction between pile-soil. Some examples are analyzed and indicate that along with the increasing load the distribution of axial load and rigidity of single pile become uniform. Compared with various types of pile group, the pile group in circle distribution contributes to bear inclined load, and the axial load of each pile is more uniform. Under the vertical load, the vertical pile group has bigger bearing capacity than the battered pile group. Under lateral load, the positive battered pile group has bigger bearing capacity than the vertical and negative battered pile group.Both model experiments and prototype experiments are conducted. The model experiments results indicate that the pile group composed of extending all around piles can bear inclined load better. This is beneficial to the foundation of transmission tower. The prototype experiments results indicate that the micropile’s load capacity is satisfied with design. The efficiency of the pile group is about 0.9. According to the geology of experiments, the results of presented method agree well with those of theexperiments. This further proves that the generalized elastic theory is reasonable and reliable.更多还原