土对桩中波传播特性影响及小波分析研究

RESEARCH ON CHARACTERISTICS OF WAVE PROPAGATION IN PILE ENCLOSED BY SOILS

采用数值分析方法,对桩周土模量及阻尼系数对桩中波速及幅值衰减系数影响规律进行系统研究,结果表明,波速随桩周土模量增大而增大,随阻尼系数增大而变小;波幅衰减系数随土模量和阻尼系数增大而增大,衰减系数与波速间近似成负线性相关规律。数值计算及实测资料表明,随着激振力脉冲长度增大,波传播速度变大,吸收系数变小。不同频率成份波传播特性的差异,表明桩周土对波具有频散和耗散特性,土的频散与耗散特性可以采用小波分析技术来研究。

The variation of velocity and the absorption coefficient of waves in piles enclosed by soils with different Young modulus and damping coefficients are studied systematically by means of numerical analysis. It is shown that the wave velocity decreases with the decreasing of Young modulus and increasing damping coefficients; and the absorption coefficient increases with the increasing of Young modulus and damping coefficients. The absorption coefficient and wave velocity are approximately of negative linear correlation. The result of numerical calculation and measured data show that, when the excitation pulse width becomes bigger, the propagation velocity increases and the damping coefficients decrease. As the transmitting characteristics are different for pulses with different frequency components; the soils around the pile has the frequency dispersion and dissipation effect on the waves. The measured curve can be decomposed into different waveband components by wavelet analysis. The characteristics of dispersion and dissipation of soils to waves can be investigated by comparing the excited signal and the reflection curve.