桩身浅部缺陷数值分析及实例

Numerical analysis and example of shallow defects in pile

在桩身完整性分析中,为确定缺陷的性质和准确位置,依据弹性波理论,提出了利用数值计算手段分析不同类型桩身浅部缺陷的新方法。结论表明,缺陷附近的阻抗变化与反射波幅大小成正比。对浅部缺陷,可以近似用无阻力反射系数来估算缺陷的大小;对突变缺陷桩,由"峰-峰值"来确定缺陷的位置,用速度波曲线的负峰、正峰间距确定缺陷的长度较准确;桩身浅部缺陷,选用窄脉冲激励较易分析;该方法也可以用来模拟多个缺陷、桩身形状或密度变化情况。该成果为定量分析桩完整性提供了有益的理论参考和实践依据。

In order to determine character of the defect and its exact location, a new method is proposed through numerical calculation in pile integrity analyses, which is based on the elastic wave theory. The conclusion indicate： the variety of impedance is proportional to the wave amplitude. For the shallow defect, the size of the defect could be estimated by reflecting coefficient, whose impedance is not considered. For the break defect, the location could be confirmed by peak to peak. The defect length could be estimated by the space between negative peak and positive peak of velocity wave. It is easy to analyze the shallow defect by narrow plus. The new method could be used to simulate multi-defect, pile shape or density variety. It provides beneficial practical and theoretical reference to perform the quantitative analysis for the technicians of pile integrity.