Experimental study on rock damage and failure induced by multi-source dynamic disturbances

• The coupling effect of intermediate and low-frequency disturbance decreases the σ p by 8.1%−9.8%. • The granite presents a complex tension-shear failure mode induced by multi-source disturbance. • Intermediate−frequency disturbance increases the E and decreases the brittleness of rock. • Resonance effects lead to an increase in disturbance energy and a significant decrease in σ p . Research into the mechanical behaviour of rock surrounding the deep-buried tunnel under multi-source dynamic disturbance is key to the safety of underground engineering operations. Based on a dynamic true-triaxial testing apparatus, the present study examined the mechanical behaviours and fracture mechanisms of deep granite under the coupled effects of intermediate-frequency dynamic disturbance ( f = 300 Hz) and low-frequency dynamic disturbance ( f = 5–20 Hz). Intermediate-frequency dynamic disturbance markedly initiates the genesis of tensile micro-cracks within rock, while low-frequency dynamic disturbance exacerbates the propagation and interconnection of cracks, ultimately leading to the formation of a tensile-shear mixed failure mode. The severity of the influence of intermediate-frequency disturbance on the peak strength of rock is the initial crack compaction σ cc (decreased by 8.1%), the damage stress σ cd (decreased by 6.4%), and the crack initiation stress σ ci (decreased by 4.7%) under different disturbance timings. This changes the characteristic stress of the rock and significantly decreases its brittleness index. Meanwhile, the low-frequency f of weak disturbance significantly affects the failure mode and peak strength of the rock. The peak strength σ p exhibits U-shaped variation, with the maximum decrease reaching 15 MPa, which indicates the presence of a resonance effect between the external disturbance and the natural frequency of the rock. The timing of intermediate-frequency disturbance alters the natural frequency of the rock. Analysis of the fracture surface shows that cracks induced by intermediate-frequency disturbance primarily propagate along the σ 1 -direction, while low-frequency disturbance promotes propagation of shearing cracks along the σ 3 -direction. Brittle failure occurs due to the through-going shearing cracks. The results further reveal the synergistic mechanism of action of multi-source dynamic disturbance on rock failure, indicating that the coupled effects of multi-source dynamic disturbances significantly increase the risk of brittle failure in the rock mass.