基于多重互相关函数分析剪切波速

介绍了一种提高单孔法剪切波速测量精度的新方法-多重互相关函数法。考虑到判断场地剪切波到时差的困难，提出了用多重互相关函数来求得两剪切波的到时差。互相关分析可求取两相似信号的到时差，但当两信号相似性比较差时，所求得到时差的误差较大；自相关函数本身可进行多重自相关分析，互相关函数结合多重自相关函数后，也可以进行多重互相关分析来求取两相似信号的到时差。试验表明：相比互相关函数，多重互相关函数可改善触发信号和井中三分向探头输出信号的相似性及更好地抑制噪声，因此能更精确地计算出触发信号和井中三分向探头输出信号的的到时差。基于此原理设计了剪切波波速的测试系统,此系统能自动分析出测点的剪切波速和形成完整的报告。

Analysis of shear wave velocity based on multiple cross-correlation functions

A new wave arrival time difference detection method based on cross-correlation functions for shear wave velocity measurement in single-hole method is introduced. As the difficulty to analyze the arrival time difference of shear wave velocity, the multiple cross-correlation function is used to get the arrival time difference of two similar shearwave velocities. We need do multiple-auto-correlation function to the signal with big noise to get high SNR. Cross-correlation function can get the arrival time difference of two similar signals, but the error is always too big when the nose of signal is big. The auto-correlation function can do multiple auto-correlation analyses; and the cross-correlation also can do multiple cross-correlation analysis with multiple auto-correlation function. The experiments indicate: multiple cross-correlation function can increase the SNR and get the arrival time difference precisely of the signal of shear wave acquainted by trigger and the shear-wave acquainted by probes. Based on this principle, an expert recognition system to calculate shear wave velocity is designed. This system can automatically analyze the shearwave velocity of every measured point and make a complete report.