Evaluation of Ultrasonic Measurement Systems for Bolt Load Determinations

摘要

The U.S. Bureau of Mines has developed ultrasonic measurement instrumentation capable of measuring strains and elongations of tensioned and untensioned mine roof bolting systems. The report evaluates the pulsed-phase-lock-loop and pulse-echo systems. The pulse-echo systems measure time of flight of a signal through the bolt. The ultrasonic instrument converts the measurement into elongations or stress. The most recent Bureau instrument development converts travel-time measurements directly into elongation, load, stress, and torque by simple data manipulation from the keyboard. Bolt preparation and instrument calibration are described in detail.