Numerical Study on Blast Dynamic Response of Jointed Rock Mass under High Geostress Field

Abstract

To study the blast-induced dynamic response of jointed rock mass under high geostress field, a numerical model for the blast in the jointed rock mass was first established based on Ansys LS-DYNA software and the Riedel–Hiermaier–Thoma (RHT) constitutive model. Subsequently, the influence mechanism of different initial geostress fields and joint distributions on stress wave propagation was explored. Finally, the energy transmission process of stress wave and the damage evolution characteristics of the jointed rock mass were analyzed. The numerical simulation results show that the blast stress wave causes the fluctuation in the peak radial stress of rock on the near-explosion side of the joint under different joint distributions. The difference in the peak radial stress gradually diminishes as the propagation distance increases. The peak radial stress of rock under geostress is affected by the rock fracture type, while the lateral pressure coefficient has little effect. The evolution process for peak tensile stress on the back-explosion side of the joint can be divided into three stages: (1) stress attenuation; (2) stress strengthening; and (3) continuous stress attenuation. In the absence of geostress, the energy transmission coefficient varies with the generalized normal stiffness of the joint and the incident angle of the cylindrical stress wave. When the initial geostress is applied, the energy dissipation of the stress wave that corresponds to the joint reduces, and the energy transmission coefficient increases. The consumption of explosion energy is mainly distributed in a small range around the blasthole compared with the state without geostress; therefore, the geostress significantly reduces the damage to the surrounding rock. The rock-breaking efficiency is better when the lateral pressure coefficient is smaller, and the damage degree of the rock on the back-explosion side of the joint under certain geostress is exacerbated. In addition, the geostress has an inhibiting effect on the formation of wing cracks.