Abstract:

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.

Key words: multiple cross-correlation functions, shear wave velocity, arrival time difference, single-hole method