An automatic extraction algorithm for measurement of installed rock bolt length based on stress wave reflection

A rock bolt is a reinforcing bar commonly used in geotechnical engineering, and it plays an important role for the safe operation of the reinforced structures, such as tunnels, underground stations, and stabilized slopes. The length of an installed rock bolt is an important quality index that ensures the performance of a rock bolt for the stability of the reinforcing structure. In this paper, based on the general principle of stress wave propagation, the method of Automatic Extraction Algorithm (AEA) is developed using self-correlation analysis to measure the length of an in-service rock bolt, whose length is mostly embedded. The propose method has advantages of simple computation and high accuracy. Through laboratory experiments and field tests, we compared the performances of AEA with the traditional Phase Analysis Method (PAM) and the results demonstrated that the proposed AEA showed improved performance in terms of both detection speed and accuracy in rock bolt length estimation. In addition, the AEA method was successfully implemented in several engineering scenarios with high accuracy.