Applications of the Continuous Wavelet Transform Method in Crosshole Sonic Logging Tests

摘要

Crosshole Sonic Logging tests are commonly used to determine the integrity of drilled shafts. However, selections of signal arrival times can be subjective. Different persons may pick different arrival times from the same record. The lack of consistency can be a source of disputes. This paper proposes use of the integrated continuous wavelet transform (IC WT) method, which applies continuous wavelet transform to interpret direct arrival measurements. The key feature of the method is transferring a nonlinear sinusoidal-like signal to a linear phase angle plot. Peaks in the recorded signal are shown as 0-degree phase. By selecting the time point of 0 degrees with an amplitude above the noise level, the arrival time of the first peak can be uniquely identified. This method removes subjectivity between operators. The ICWT method can also be used for other tests that measure travel time intervals (i.e. pulse echo and seismic CPT tests).