Analysis of the damage mechanism of strainbursts by a global-local modeling approach

Abstract

Strainburst is the most common type of rockbursts. The research of strainburst damage mechanisms is helpful to improve and optimize the rock support design in the burst-prone ground. In this study, an improved global-local modeling approach was first adopted to study strainburst damage mechanisms. The extracted stresses induced by multiple excavations from a three-dimensional (3D) global model established by fast Lagrangian analysis of continua in 3 dimensions (FLAC3D) are used as boundary conditions for a two-dimensional (2D) local model of a deep roadway built by universal distinct element code (UDEC) to simulate realistic stress loading paths and conduct a detailed analysis of rockburst damage from both micro and macro perspectives. The results suggest that the deformation and damage level of the roadway gradually increase with the growth of surrounding rock stress caused by the superposition of mining- or excavation-induced stresses of the panel and nearby roadways. The significant increase of surrounding rock stresses will result in more accumulated strain energy in two sidewalls, providing a necessary condition for the strainburst occurrence in the dynamic stage. The strainburst damage mechanism for the study site combines three types of damage: rock ejection, rock bulking, and rockfall. During the strainburst, initiation, propagation, and development of tensile cracks play a crucial role in controlling macroscopic failure of surrounding rock masses, although the shear crack always accounts for the main proportion of damage levels. The deformation and damage level of the roadway during a strainburst positively correlate with the increasing peak particle velocities (PPVs). The yielding steel arch might not dissipate kinetic energy and mitigate strainburst damage effectively due to the limited energy absorption capacity. The principles to control and mitigate strainburst damage are proposed in this paper. This study presents a systematic framework to investigate strainburst damage mechanisms using the global-local modeling approach.