Measurement of elastic parameters of dry sand using bender-extender element

Abstract

利用安装在共振柱测试系统中的弯曲-伸展元，开展了干砂中P波（压缩波）和S波（剪切波）的室内试验，详细地分析了干砂中P波和S波的信号特征，研究了输入频率、土体密实度和有效围压对输出信号的影响。对比各种信号分析方法，并参考共振柱试验结果确定了S波的传播时间。根据实测波速和波动理论，确定了土体的弹性参数，包括剪切模量，侧限模量和泊松比。研究结果表明，P波和S波的输出信号频率在一定程度上随输入信号频率、土体密实度和有效围压的增加而增加，且P波信号比S波信号更容易确定波的传播时间；土体的弹性模量随土体密实度和有效围压的增加而增加，但剪切模量增长比侧限模量快；土体的泊松比并非一个常数，随着土体密实度和有效围压的增加而下降。初步探讨了利用剪切模量估算泊松比，以方便实际工程应用。 The compression wave (P-wave) and shear wave (S-wave) in dry sand are measured simultaneously by a bender-extender element incorporated in a resonant column apparatus. The characteristics of the output P-wave and S-wave signals are analyzed; and the effects of the input signal frequency, soil density and effective confining pressure on the signal characteristics are investigated. According to the wave propagation theory and measured S-wave and P-wave velocity, the elastic properties of the dry sand are calculated, including shear modulus, constrained modulus and Poisson’s ratio. The results indicate that to some extend the frequency of the output signal increases with increasing input frequency, soil density and effective confining pressure. Compared with S-wave, it is easier to determine the P-wave travel time and thus the wave velocity. The elastic modulus of the soil increases with increasing density and effective confining pressure, especially the shear modulus. The Poisson’s ratio decreases with increasing density and confining pressure, instead of a constant. Attempt is also made to estimate the Poisson’s ratio based on shear modulus considering the convenience of application in the practical engineering.