Mechanical Behavior of Fully Grouted GFRP Rock Bolts under Multiple Blast Dynamic Loads

Abstract

Glass-fiber-reinforced plastic (GFRP) bolts, renowned for their excellent corrosion resistance and high tensile strength, are widely used in tunnel supports. However, in practical engineering, GFRP bolts are susceptible to damage from multiple blast loads, making the study of their mechanical behavior under such dynamic conditions essential. This study developed a numerical model of fully grouted GFRP rock bolts under multiple dynamic loads, aiming to accurately simulate their mechanical behaviour under multiple blasts in practice. Moreover, the axial force characteristics of GFRP bolts in field conditions subjected to multiple blasts were monitored using force-measuring bolts. The study showed that under multiple blasts, the axial stress along the bolt decreased exponentially within a distance from the bolt collar, with the maximum axial stress occurring at the bolt collar. As the number of blasts increases, there is an overall escalation in axial stress throughout the bolt, most notably in the maximum axial stress. Concurrently, the rate of stress decreases faster, and the stress distribution extends to the deeper anchoring sections. With the intensity of the blast dynamic load increasing, the maximum number of blasts the bolt can withstand decreases following an exponential function, exhibiting a two-stage characteristic of a rapid decrease followed by a slow decrease. In addition, the cumulative characteristics of maximum axial stress in GFRP bolts compared to metal bolts under multiple dynamic loads show significant differences. The results of this study can provide a theoretical basis for the design of GFRP bolt support systems and the optimization of blast control under multiple blasts.