Blasting induced dynamic stress concentration and failure characteristics of deep-buried rock tunnel

Abstract

In this study, the dynamic stress concentration factors (DSCF) around a straight-wall arch tunnel (SWAT) were solved analytically utilizing the complex variable function methods and Duhamel’s integral. The effects of wavelength, incident angle, and blasting rising time on the DSCF distribution were analyzed. Theoretical results pointed out dynamic disturbances resulting in compressive stress concentration in the vertical direction and tensile stress in the incident direction. As the wavelength and rising time increased, there was a tendency for the amplitude of stress concentration to initially rise and then converge. Moreover, a series of 3D FEM models were established to evaluate the effect of different initial stress states on the dynamic failure of the tunnel surrounding rock. The results indicated that the failure of the surrounding rock was significantly influenced by the direction of the static maximum principal stress and the direction of the dynamic disturbance. Under the coupling of static and blasting loading, damage around the tunnel was more prone to occur in the dynamic and static stress concentration coincidence zone. Finally, the damage modes of rock tunnel under static stress and blasting disturbance from different directions were summarized and a proposed support system was presented. The results reveal the mechanisms of deep-buried rock tunnel destruction and dynamically triggered rockburst.