Experimental study on low frequency guided wave propagation in grouted rock bolt

Experiments were carried out to investigate the propagation properties of low frequency longitudinal guided waves in grouted bolts and free bolts. A series of free bolts specimens and grouted bolts specimens were prepared, and experiments were conducted at different frequencies. Several characteristic parameters such as the first echo time and velocities were extracted. The properties of grouted bolts were retrieved using the test results of free bolts, and fixed deviations caused by equipments and other factors were extracted. The velocities of the guided waves in free bolts were derived after the fixed deviations corrected and then the test results of grouted bolts were retrieved with the corrected velocities and the fixed deviations, which can improve the precision of the test results and lay the foundation for the inspection of grouted bolt with ultrasonic guided waves.