A non-destructive length measuring method for mine-used bolt or anchor cable

For problems of complex operations and low measuring precision of existing length measuring methods for bolt or anchor cable, a non-destructive length measuring method for mine-used bolt or anchor cable was proposed which was based on magnetostriction guided wave technology. Length measuring principle of bolt or anchor cable, design scheme of a measuring system and measuring operations were introduced. Speed of the measuring system was calibrated and length of bolt in concrete structure was measured in lab. The experimental results show that the method has the maximum error of 2.66% and average error of 0.33%, which satisfies application requirement of length measurement of mine-used bolt.