Electromagnetic Launching System as an Alternative to Non-Destructive Sonic Wave Generation for Steel Bar Length Determination
Keywords:Bar length evaluation; Electromagnetic launcher; Non-destructive technique; Sonic wave., bar lenght evaluation, electromagnetic launcher, non-destructive technique, sonic wave
The installed length of nails and ground anchors widely used in retaining structures should be known in order to verify design and to ensure slope stability. Non-destructive techniques have been used to evaluate retaining wall buried steel bars. Sonic Echo and Impulse Response techniques evaluate the bar length using sonic wave propagation through an impact performed by the test operator with a hammer. Results may be affected by this non-standard procedure. This paper aims to propose an automated sonic wave generation in order to carried out quick test with reproducibility and without operator dependence. An electromagnetic launching system was developed, which uses a projectile in place of the hammer and the electromagnetic force instead of human force. The system details are presented in this study and the projectile output speed optimization and impact reproducibility are analyzed. The sonic data was received by a microphone, which was digitized and sent to the computer by a microcontroller, making the system compact and portable. Steel bars length were obtained by both time and frequency domain data analysis. Results shown high reproducibility when performed under the same initial condition. The propagation velocity error was less than 1% for steel bar with length of 1 m.