Dynamic Response and Failure Analysis of Underground Openings to Oblique Wave Incidence

Abstract

In deep underground mine, besides the high static in situ stress, openings such as stopes, drifts, and shafts in underground mine are also frequently subjected to dynamic waves coming from blasting and earthquake. The interactions of these waves with the opening boundaries can be under arbitrary incident angles and thus would induce different damages. In order to investigate the dynamic response of openings under the oblique incidence of blasting load, numerical modeling of wave incidence to a rectangular opening at different incident angles and the associated dynamic failure was carried out under various in situ stress states. The numerical model established by the discrete element code PFC2D was first validated against theoretical results for reflection of oblique wave incidence at the free surface at various incident angles. The simulation results showed that the reflected P wave causes spalling around the opening, and the subsequent reflected SV wave further promotes the propagation of tensile cracks. Among them, the opening with vertical wave incidence is the most seriously damaged, while wave incidence at 15° and 30° angles results in similar damage degree on the incident side of the opening. The damage of the opening at a 45° incident angle is light. With the increase of burial depth, the position of spalling at the incident side gets closer to the sidewall of the opening. When the buried depth is 1,200 m, the largest number of cracks around the opening is achieved for wave incidence at a 45° angle. This research can improve the understanding of the resulting failures from stress-wave incidence to the openings at arbitrary angles and contribute to the design of the opening in the deep underground.