Dynamic response of rock bolts to blasting vibrations

In order to study the influence of blasting vibrations on rock bolts in support structures, the law of bolt response to blasting vibration was studied by means of the theory of structural dynamics in this paper. The displacement, velocity and axial force of the bolt were derived. The study shows that the dynamic responses of the bolt are different in the anchored and free sections. The velocity and axial force of the free section attenuate exponentially. However, the velocity and axial force of the anchored section vary in a sinusoidal way. Both the length of the anchored section and the shear stiffness of the grout influence the vibration of the rock bolt, and the stresses are different in different anchor lengths. The anchored length can be reduced somewhat on the premise that the bolt would fail in tension. The higher the shear stiffness of the grout is, the higher the shear stress is. Therefore, the rigidity of the grout material should not too high in order to prevent shear damage on the bolt.