钻孔灌注扩底桩抗拔承载力及耐久性研究

发布时间：2019-01-30 14:14

【摘要】：钻孔灌注扩底桩是近年发展起来的一种新的桩型,相比传统的钻孔灌注桩具有更高的承载力,已经成为大型工程普遍采用的一种基础形式。随着大型市政设施、大跨桥梁、超高层建筑等建(构)筑物及超大面积的纯地下室的建设,近年来钻孔灌注扩底桩在国内工程界逐渐得到广泛应用。目前,对扩底桩的理论研究还不完整,扩底桩的实际承载能力都是通过现场荷载试验确定。然而试验不仅花费时间长、耗资巨大、代表性差,而且很难测出完整的Q-S曲线。因此有对扩底桩的承载性状进行探讨的必要性,提出更加符合实际的扩底桩极限承载力的理论计算方法。另外由于钻孔灌注扩底桩在使用过程中要不断接触水和土壤,导致其中的有害物质会侵蚀桩体,造成钻孔灌注扩底桩耐久性裂化,并对上部结构产生影响。本文选用了ANSYS数值计算软件建立了扩底桩桩土相互作用模型,对扩底桩的受力性状进行了深入细致的探讨和分析。研究的主要内容有： (1)论述了钻孔灌注扩底桩的抗拔破坏机理及现有抗拔承载力计算方法。 (2)采用平面有限元方法,利用通用有限元软件ANSYS建立轴对称分析模型,计算了不同情况下桩-土的竖向位移,得出了钻孔灌注扩底桩的抗拔极限荷载。 (3)针对沿海环境,指出了氯盐环境下钻孔灌注扩底桩的腐蚀机理,建立了氯离子在钻孔灌注扩底桩内的侵蚀模型和对应的耐久性极限状态,根据工程参数提出了相应的寿命预测方法,对不同水灰比、保护层厚度、暴露区域的混凝土失效概率进行了分析计算。并针对大部分工程提出了一些加强混凝土抗氯离子侵蚀的措施。 (4)最后针对北方严寒地区的钻孔灌注扩底桩,论述了其经受冻融循环破坏的机理和常见损伤破坏形式,提出了一些提高钻孔灌注扩底桩抗冻融循环损伤的措施。
[Abstract]:Bored cast-in-place reamed pile is a new type of pile developed in recent years. Compared with the traditional bored pile, it has higher bearing capacity and has become a basic form widely used in large-scale projects. With the construction of large municipal facilities, long-span bridges, super-high-rise buildings and super-large area pure basement, bored cast-in-place reaming piles have been widely used in the domestic engineering field in recent years. At present, the theoretical study of reamed pile is not complete, and the actual bearing capacity of belled pile is determined by field load test. However, the test is not only time-consuming, costly and unrepresentative, but also difficult to measure a complete Q-S curve. Therefore, it is necessary to discuss the bearing capacity of reamed pile, and a theoretical calculation method of ultimate bearing capacity of belled pile is put forward. In addition, due to the continuous contact with water and soil during the use of the bored cast-in-place reaming pile, the harmful substances in the pile will erode the pile body, resulting in the durability cracking of the bored cast-in-place reaming pile and the influence on the superstructure. In this paper, the ANSYS numerical calculation software is used to establish the pile-soil interaction model of the reamed pile, and the mechanical behavior of the belled pile is discussed and analyzed in detail. The main contents of the study are as follows: (1) the mechanism of uplift failure of bored cast-in-place reamed pile and the existing calculation methods of uplift bearing capacity are discussed. (2) using the plane finite element method and the general finite element software ANSYS, the axisymmetric analysis model is established, the vertical displacement of pile-soil under different conditions is calculated, and the ultimate uplift load of bored cast-in-place reamed pile is obtained. (3) aiming at the coastal environment, the corrosion mechanism of bored cast-in-place reaming pile under chloride environment is pointed out, and the corrosion model and the corresponding durability limit state of chloride ion in bored cast-in-place reaming pile are established. According to the engineering parameters, the corresponding life prediction method is put forward, and the failure probability of concrete in different water-cement ratio, cover thickness and exposed area is analyzed and calculated. Some measures to strengthen the chloride corrosion resistance of concrete are put forward for most of the projects. (4) at last, aiming at the bored cast-in-place reaming pile in the cold area of northern China, the mechanism and common damage forms of the pile subjected to freeze-thaw cycle are discussed, and some measures to improve the anti-freezing and thawing damage of the bored cast-in-place pile are put forward.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU473.1

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