【作者】 智胜英；

【导师】 王建华；

【作者基本信息】 天津大学 ， 岩土工程， 2008， 博士

【摘要】 在当前的实际工程中,进行基桩缺陷定量分析仍然存在一定难度。为了建立考虑桩土相互作用的低应变基桩缺陷定量分析方法,本文进行了以下几方面的工作:依据一维波动理论建立并求解了低应变基桩阻尼波动方程。为了分析不同参数对速度波沿桩身衰减过程的影响,利用得到的解析解进行了正交试验。试验结果表明,针对不同工程情况可以在速度波波幅比与桩土相互作用阻尼系数之间建立一致的函数关系。进一步针对特定试验情况,建立了速度波波幅比与阻尼系数的相关关系,据此提出了依据桩顶速度响应确定桩土相互作用阻尼系数的方法。结合速度波沿桩身传播过程中的衰减规律和波阻抗变化处的能量分配关系,分析速度波的传播过程,进而针对不同缺陷个数和不同桩侧土分层条件得到了基桩缺陷定量分析的关系式。针对6种桩侧土进行桩土相互作用模型试验,实际测定了试验土在不同状态时的桩土相互作用阻尼系数。进而对应模型试验进行剪切波速试验,依据试验结果建立了阻尼系数和剪切波速之间的相关关系。利用理论公式确定实测阻尼系数相应的理论阻尼系数,结果表明,理论阻尼系数应用于实际工程时需要进行修正,修正系数是剪切波速的函数。另外,高应变阻尼系数结果相对实测阻尼系数有一定误差。为了将依据剪切波速确定阻尼系数的方法推广到其他种类土,重新选择了两种砂土进行完整桩模型试验和剪切波速试验,结果表明,计算得到的阻尼系数与试验测得的结果基本一致。利用计算阻尼系数和基桩缺陷定量分析关系式对均质土中缺陷模型桩进行缺陷定量分析,结果表明,计算得到的缺陷程度与实际缺陷程度基本一致。利用小波分析方法处理基桩动测信号,发现单支重构得到的逼近信号中可以凸显桩深部微弱信号。更多还原

【Abstract】 At present, it is still very difficult to determine the degree of pile defect quantitatively in engineering practice. In order to establish a new low-stain method to realize quantitative analysis of pile defects considering pile-soil interaction, researches have been done as following.The pile wave equation with damping is developed with one dimension wave theory considering pile-soil interaction. Using the analytic solution of the equation, orthogonal tests were conducted to analysis the effect of different parameters on the attenuation rule of velocity wave along pile shaft. The result showed that the coincident functional relationship between wave amplitude ratios and pile-soil interaction damping coefficient could be determined corresponding to different projects. Then, the relation between the damping coefficient and amplitude ratio of reflected velocity wave to incidenced velocity wave on pile top was established. Then a method to determine damping coefficient of pile-soil interaction was developed based on velocity response of pile top.The transmitting process of velocity wave was analysed based on the attenuation rule of velocity wave along pile shaft and the distribution relations of enegy where wave impedance changed. Corresponding to different numbers of defects and different beds of strata, the relationship for quantitative analysis of pile defects was determined.The pile-soil interaction model tests were proceeded to measure the pile-soil interaction damping coefficient of six different kinds of soils. Then, shear wave velocity experiments were proceeded corresponding to the conditions of pile-soil interaction model tests. With the result, the relationship between the damping coefficient and shear wave velocity was founded. Then, the theoretic damping coefficient were determined with the theoretic formular. Result showed that theoretic damping coefficients should be corrected in engineering practice, and the correction factor was a function of shear wave velocity. Moreover, corresponding to the result of measured damping coefficients, high-stain damping coefficients have a great error. Therefor, it is improper to apply high-stain damping coefficients in low-stain conditions.In order to spread the method of determing damping coefficient with shear wave velocity, model test of integrated pile and shear wave velocity experiments using two kinds of sand were conducted. Results showed that calculated damping coefficients were consistent with test results.The quantitative analysis of pile defects of defective model pile in the homogeneous soil had been done with calculated damping coefficient and the relationship of quantitative analysis of pile defects. The result showed that the calculated degree of pile defects was consistent with the actual result.The velocity signals on pile top were dealed with wavelet analysis method. The decomposing result showed that smallscreen of pile bottom appeared in the the approximation signal.更多还原