Examination of the impact of elliptical cavities on the propagation law of stress waves within the tunnel surrounding rock

Abstract

To examine the effects of elliptical cavities on the dynamic stability and failure patterns of straight-walled arched tunnels, this study utilizes a modified drop-weight impact test apparatus for dynamic experiments and performs numerical simulations via AUTODYN software. The research examines stress wave attenuation, energy dissipation, and the evolving characteristics of the stress field around the elliptical cavity through both experimental and numerical approaches. The findings reveal that elliptical cavities significantly obstruct stress wave propagation, resulting in considerable attenuation of peak stress amplitude and notable energy dissipation. The crack coalescence is observed between the tunnel crown and the rock bridge beneath the elliptical cavity, which leads to shifts in the stress field. Notably, the location of maximum circumferential stress deviates by approximately 10° for the inclination angle of θ = 45°. The results are indicative of the fact that the stability of the tunnel is highest under horizontal stress waves (θ = 90°) and lowest at θ = 45°, where damage initiation and stress concentration primarily occur at the haunches. Further, the dominant coalescence modes vary with cavity inclination: crown crack coalescence at θ = 0° and 15°, shoulder crack coalescence at θ = 30°, 45°, and 60°, and sidewall crack coalescence at θ = 75° and 90°. The tunnel shoulders and sidewalls represent the most vulnerable zones, exhibiting the highest susceptibility to failure.