【作者】 张敏；

【导师】 马建林；

【作者基本信息】 西南交通大学 ， 岩土工程， 2014， 博士

【摘要】 本论文依托国家重大工程项目港珠澳大桥的建设,并在以往有关研究成果的基础上,通过开展大直径钢管复合桩室内模型试验,对复杂受力条件下钢管复合桩在考虑管内剪力环、泥皮和防腐涂层存在条件下的工作性能进行了深入研究,为钢管复合桩设计提供试验和理论依据。本文具体开展的工作如下：1、通过开展9组钢管复合桩力学性能试验,对剪力环、泥皮和防腐涂层不同组合条件下的钢管复合桩受力特性和变形规律进行研究。结果表明,钢管复合桩明显改善无钢管钢筋混凝土桩的承载性能和变形特性。(1)钢管复合桩较无钢管钢筋混凝土桩具有更好的承载能力。在试验条件下,考虑泥皮、防腐涂层和剪力环(间距3D)的钢管复合桩的承载能力约为无钢管钢筋混凝土桩的1.9倍；(2)泥皮和防腐涂层的存在降低了钢管复合桩的承载能力和改变了变形特性。试验条件下,泥皮和防腐涂层分别使其抗压刚度降低了3%,抗弯刚度分别降低了1%和1%～2%,但弱化影响较小且在工程控制精度允许范围内；(3)剪力环明显改善了钢管与核心混凝土的受力特性。在试验条件下,剪力环间距为1D～3D时,钢管复合桩截面变形相继出现了“倒v”或“m”型分布,表明剪力环有效地将核心混凝土的应力传递至钢管。剪力环间距为2D(60cm)时,钢管复合桩的受力及变形较为合理。2、在对试验结果研究的基础上,对压-弯-剪组合受力条件下,钢管复合桩在泥皮、防腐层和剪力环不同组合条件下的协同工作性能、套箍效应、工作机理和承载性能进行了系统研究。(1)在泥皮、防腐涂层、剪力环(间距3D)存在条件下,钢管的约束效应使核心混凝土强度显著提高；(2)钢管与混凝土的复合承载能力大于钢管+核心混凝土桩单独承载能力之和。在试验条件下,钢管套箍效应使钢管复合桩(带剪力环、泥皮、防腐涂层、D/t=100、间距3D的剪力环)承载力较钢管桩承载力与混凝土桩承载力简单之和提高9.8%：(3)采用叠加原理,给出了弹性变形阶段钢管复合桩的刚度计算公式,并进一步探讨了剪力环间距对组合刚度的影响规律。试验条件下,剪力环增强效应与其间距成双曲线关系。(4)对钢管复合桩单桩承载力的计算方法进行探讨,得出规范ACI(2005)方法适合于考虑泥皮、防腐涂层、剪力环共同存在时按内部强度控制标准计算钢管复合桩极限承载力的结论。3、通过5组钢管复合桩推出试验,着重研究了泥皮、防腐涂层和剪力环对钢管复合桩内部粘结强度的影响规律、钢管-核心混凝土界面粘结机理和界面粘结应力分布规律。指出泥皮和防腐涂层的存在使钢管复合桩的钢管与混凝土之间的粘结减弱,剪力环的设置则改善了钢管与核心混凝土之间的粘结-滑移性能。(1)在试验范围内,压-弯-剪复杂荷载条件下,钢管与核心混凝土之间的粘结强度为0.242～0.404MPa,粘结破坏时相对滑移量均小于0.2mm；(2)剪力环(间距<2D)使钢管复合桩在泥皮、防腐涂层共同存在时的粘结强度提高了66.7%,使钢管与混凝土之间具有可靠的粘结；(3)对钢管与混凝土之间的相对滑移及界面粘结应力、钢管应力之间的相互关系的进行理论分析,通过假定粘结应力与界面长度之间的指数关系,推导出了界面粘结应力、相对滑移及钢管应力的解析表达式,提出了一种新的钢管复合桩粘结-滑移本构理论分析模型,并得到试验结果的验证。4、通过采用有限元软件ABAQUS对钢管复合桩在压-弯-剪复合受力状态下的工作性能进行更深入的研究。通过选取合理的单元类型,对剪力环间距和截面形式、钢管壁厚等参数的敏感性进行分析。更多还原

【Abstract】 At the background of National Important Project, HongKong-ZhuHai-Macao Bridge, the large diameter steel tubular composite (STC) pile model tests are conducted. Shear-ring, drilling mud skin and anti-corrosion coating are considered under complex force combinations in an attempt to specify the different performances. Research results provide theoretical and testing reference to STC pile design.The detailed works include:1. Nine STC piles tests were performed with different combinations of shear-ring, drilling mud skin and anticorrosion coating. Bearing capacity and the deformation of reinforced concrete pile see better improvement when the STC pile is applied.(1)The bearing capacity of the STC piles with shear-ring, drilling mud skin and anticorrosion coating is 1.9 times of the reinforced concrete piles. So the STC piles obviously have a better capacity.(2) Drilling mud skin and anticorrosion coating could induce the reduction of deformation characteristics and carrying capacity of STC pile. Experimental results show that, compressive stiffness and decreased by 3% and 1% respectively (thickness of about 0.1 mm). Flexural rigidity fell by around 1% and 1%～2% respectively. The influence is relatively small and manageable.(3) Deformation performance and carrying capacity of pipe and core concrete of pile are improved significantly by shear-ring. Under the experimental conditions in which shear-ring spacing is set from 1D to 3D, cross-sections see inverted "v" or "m" distribution of train. It indicates the stress from core concrete is effectively transferred to pipe by shear-ring. In addition, performances are best improved if shear-ring spacing is set as 2D (60cm)2. Based on the test results, systematic research begins in an effort to find the collaborative work performance, working principle, confining effects and the bearing capacity of the STC piles. Different combinations of the drilling mud skin, anticorrosion coating and shear-ring are considered under the compressing-bending-shear forces.(1)The confining effect increases the strength of core concrete due to the co-working of drilling mud skin, anticorrosion coating and shear-ring (spacing of the shearing ring is 3D).(2)The complex carrying capacity of STC pile is greater than the total carrying capacity of steel pipe and core concrete pile. Under the experimental condition, STC pile (with shear-ring, drilling mud skin, anticorrosion coating, D/t=100, shear-ring spacing=3D) carrying capacity increased by 9.8% compared with the sum of steel pipe and concrete pile.(3)The stiffness formula of the STC pile during the elastic deformation phase by the principle of superposition, and the effluence of the shearing ring on the stiffness is explored. Under the experimental conditions, accretive effect of shear-rings and their space are showed with a hyperbolic relationship.(4)Finally, the formula is proposed when the STC piles are loaded by the axial forces, the inner limiting capacity of the STC pile with shear-ring, drilling mud skin, anticorrosion coating can be calculated by the code ACI(2005).3. Five push-out tests provide essential materials to perform separate studies of the cohesive mechanism in pipe-concrete interface and distribution discipline of cohesive forces. Conclusively, drilling mud skin, anticorrosion coating and shear-ring all prove viable in improving bong-slip behaviors of the STC pile.(1)Pipe-concrete cohesion indicates to be 0.242～0.404MPa and a less than 0.2mm figure is found in relative slippage when cohesion area collapses, with all tests conducted under force-bending-shear force.(2)Shear-ring leads cohesion rises 66.7% when drilling mud skin, anticorrosion coating and shear-ring(spacing<2D) are all involved in the tests, indicating the cohesion at pipe-concrete is thus liable.(3)In theory, the dependence between pipe stress, cohesion at pipe-concrete interfaces and relative slippage are analyzed. Exponential relationship between cohesion and length of interface is assumed in effort to deduce the analytical expression of steel pipe stress, cohesion and relative slippage. Thus, a bong-slip constitution model is proposed and verified through the test results.4. FEM software ABAQUS proves to be applicable to perform a deeper research of performance of the STC pile under force-bending-shear forces.Validation of FEM model is verified by selecting appropriate FEM model. Based on the fundamental model, sensibility of parameters such as shear ring spacing, cross-section format and steel thickness is analyzed in the study.更多还原