桩身材料阻尼对波传播特性影响的小波分析方法

理论计算及实测资料表明,反射波法基桩动测激振信号近似为半周期正弦波,不同激振方式产生的桩顶速度脉冲信号宽度不同,相应频率成分也就不同。桩身内阻尼对不同频率谐波的幅值衰减及频散规律不同,使得不同激振方式产生的复合脉冲在同一桩中会有不同变化规律,为了使不同激振方式测试资料具有可比性,应采用相同频带进行对比。为此利用小波分析的时-频特性,通过对测试信号进行时频分解,就桩身内阻尼对不同频带信号的吸收系数及波速的影响规律进行了研究。对实测资料分析的结果表明,预制桩不同频带信号波速变化不大,但衰减系数随频率增大近似线性增加。

Wavelet analysis for the propagation of stress waves in piles

Theory analysis and the measured data are shown that excitation pulse in pile integrity testing is silimar to half-period of the sine curve,and different exciting methods produce signals with different period of time,so its frequency composition is also different.It is known that influences of pile damping on the amplitudes absorption and wave dispersion in the pile are different for different frequency compositions.In order to evaluate the pile integrity characteristics correctly the variability of the amplitudes absorption and the wave dispersion should be known for different frequency band.Wavelets analysis is used to decompose the compound signal into time domain and frequency domain.So the test results can be contrasted with the same frequency band.Utilizing the site test data,the absorption coefficient and the wave dispersion of the piles for the different frequency band are researched.