APPLICATION OF LOW FREQUENCY ULTRASONIC GUIDED WAVES ON INSPECTION OF FULL-LENGTH-BONDING RESIN BOLT

Full-length-bonding resin bolt is one of the most important reinforcing tools in the tunnel supporting of mining industry. The quality of the resin bolt embedded in rock directly affects the stability and safety of the slopes or roofs. This paper simplifies the resin bolt to a mechanic model which is a cylinder rod with cladding embedded in infinite medium. The disperse curves about the resin bolt are calculated. Propagation characteristics of low frequency longitudinal mode L(0,1) in full-length-bonding resin bolt are studied. The attenuation of L(0,1) mode between 20kHz―100kHz is very low, which indicates that the L(0,1) mode can be used in the inspection of full-length-bonding resin bolts. The velocity of L(0,1) mode in the resin bolt below 70kHz is slower than the group velocity of L(0,1) in free bolt; the velocity of L(0,1) mode in the resin bolt between 70kHz―100kHz is close to the group velocity of L(0,1) in free bolt. At the same time，the experiments about full-length-bonding resin bolt detected using ultrasonic guided wave are carried out. The Experiment results are consistent with those of theory, which shows that L(0,1) is applicable to the nondestructive testing of full-length-bonding resin bolts.