Non-destructive inspection on anchorage defect of hollow grouted rock bolt using wavelet transform analysis

Hollow grouted rock bolts are widely used in deep soft rock roadways. The density of grout has a significant influence on the anchorage quality. However, there is still a lack of effective methods to detect the grouting quality fast, accurately, and extensively. Based on the wave velocity and the law of stress wave transmission and reflection in the impedance mismatch, non-destructive experiment focused on the defect in the anchorage was conducted. The wavelet transform was used to analyze the test signals. The test results show that the free length of hollow grouted rock bolt could be accurately detected through the analysis of the stress wave signal by using the low-pass filter in the wavelet toolbox. The grouted length, defect length, and specific position of the anchorage section can be accurately detected through the analysis of the stress wave signal by using the high-pass filter in the wavelet toolbox. The research can provide experiment foundation for further study of grouting quality based on the non-destructive methods.