【作者】 赵刚；

【导师】 王雪峰；

【作者基本信息】 华中科技大学 ， 岩土工程， 2005， 硕士

【摘要】 目前国内基桩完整性测试工作中,应力波反射法是最具有代表性、应用最广泛的方法,因其具有轻便、快速、经济、准确性较高等优点而得到了工程界的普遍认可。但是,有鉴于桩身缺陷的程度无法定量计算、材料阻尼和桩周土阻力的影响无法准确掌握、多重缺陷时反射波互相迭加影响造成判断错误等问题的严重存在,这一技术仍需进一步地研究和改进。本文基于一种名为FEMLAB 的新型有限元分析程序,考虑桩材料和桩侧土阻尼的影响,给出了完整桩、缺陷性质不同的桩及三维情况下完整桩的动力响应仿真曲线。理论曲线及多组模型桩实测曲线与仿真结果的对比,验证了FEMLAB 软件的可靠性; 桩身材料阻尼对速度曲线影响的仿真计算,表明了材料阻尼将导致波形传播时出现弥散现象,最明显的特征便是桩底反射波幅度趋弱、宽度趋缓; 该仿真计算同时也表明峰-峰法测试波速不存在误差,而起跳点法不够准确。考虑桩周土阻尼,通过调试桩底耦合系数和衰减规律,完成的同场地完整桩与缺陷桩的交互数值模拟,为缺陷桩的完整性计算提供了一种新的近似方法。三维情况下完整桩不同桩长、不同桩径以及不同测点的响应计算,从理论上验证了测点距中心0.5R、0.6R 时测试效果最好这一实践经验。本文研究对于弄清完整性检测过程中各种因素对速度曲线的影响具有基础性意义。更多还原

【Abstract】 Low strain dynamic test method is the most representative and popular way of pile integrity testing presently. It has been generally accepted for its virtues such as portability, celerity, economy and high veracity. However, this technology still have many shortages. For example, the size of the defects can’t be calculated accurately, the influence of the pile material damping can’t be identified correctly,and superimposing problems of the deflection waves with many defects in a pile can’t be distinguished,Etc. In this paper, the analysis is based on a new FEM software-FEMLAB. Considering the influence of pile material damping and the soil damping, the dynamic response curves of a perfect pile, a pile with many variable defects and a pile in complicated three dimensions are calculated. By comparing the theoretical curves and the actual curves of model piles, the reliability of the software is tested. The influence of the pile material damping is analyzed, which affects the dynamic response curves obviously. The pulse width is wider, the attenuation of the dynamic response is slower. When testing the wave speed, the two peak values need to be selected if the pile material damping is considered. By simulating numerically the dynamic response curves of a perfect pile and adjusting the coupling parameters, the coarse extent of the defect can be gotten. The dynamic response of a perfect pile under complicated three-dimensions is simulated and the variable response curves of variable pile diameters and pile lengths are analyzed. It is verified that test point is put near the half of the radius of a pile. The results of the paper are significant to make clear the influence of variable defects under actual situation.更多还原