Propagation Characteristics of Blast-Induced Vibration in Parallel Jointed Rock Mass

Abstract

Parallel joints are ubiquitous in geological rock mass and seriously affect rock excavation in underground mining and civil engineering. In this study, the propagation characteristics of shock waves subjected to blasting load in a parallel jointed rock mass were investigated using field testing and three-dimensional finite-element numerical modeling. The method of instantaneous energy was first adopted to mine the recorded information about the interaction between joint planes and shock waves; then, the displacement discontinuity method (DDM) was used for the characterization of joint surfaces in the numerical model. The effects of joint mechanical properties, including joint spacing and joint normal stiffness, were also evaluated. The results showed that the instantaneous energy provided a powerful tool for reflecting the localized singularity of energy due to the wave reflection and superposition caused by joint planes. It is clear that the wave reflection in the component perpendicular to the joints was significant with a prolonged action time. Compared with the intact rock mass, the amplitude of shock waves in the jointed rock mass was increased by 2–3 times with highly complicated attenuation, and stress waves were divided into a series of equivalent new sources by the joints in the direction perpendicular to parallel joints. It was also found that the joint properties had a great effect on the propagation of blast-induced vibration.