Experimental study of anchor bolt stress evaluation with hybrid optical fiber monitoring

Abstract

The evaluation of mechanical properties of bolts is crucial for ensuring the long-term stability and continuous maintenance of underground engineering. Current research prioritizes the development of highly adaptable bolt mechanical behavior monitoring methods. By utilizing bolts with embedded sensors, the working status and surrounding environment can be monitored without affecting the original support structure, enabling effective disaster prevention monitoring. In this study, we introduce an innovative hybrid monitoring system based on strain gauges, Fiber Bragg Gratings (FBG), and Brillouin Optical Time Domain Analysis (BOTDA). A specialized dynamometer with temperature compensation is employed to collect axial force data under step loading conditions. We compare the sensing characteristics of various methods and derive the strain transmission coefficients of fiber sensors at different distances. The results demonstrate that the FBG and BOTDA accurately reflect the magnitude and change patterns of the monitored parameters, highlighting the potential application of this novel system for bolt monitoring. This work proposes a unique fiber optic temperature compensator and strain transmission coefficient analysis method to promote the evaluation quality of anchor bolt stress behaviors, which would provide realistic significance to enhance the accuracy and reliability of bolt mechanical property evaluation in underground engineering.