Damage and weakening effects of blasting on anchored rock mass

Abstract

Abstract During blasting excavation of roadways, dynamic load is an important cause of damage to anchored rock mass and threatens the reliability of anchoring structures. Through theoretical analysis and numerical simulation, we studied the propagation of blasting stress waves based on anchor strengthening and damage and weakening of anchored rock mass and obtained damage characteristics of anchored rock mass under blast loading. The research results demonstrate that anchorage can reduce parameters, such as Poisson’s ratio, initial damage to the rock mass, and the attenuation coefficient of blasting load therein. The main causes of damage are high blasting load and stress wave reflection on structural planes of fractures. Moreover, the damage coefficient decreases then stabilises before increasing as the rock mass changes from being anchored to being blasted. Damage under blasting load shows zonal characteristics: a severely damaged zone, a damage transition zone, and damage vanishing zone can be seen along the axis of a roadway. The worst damage in shallow parts influences the reliability of anchoring structures, while the damage transition zone shields the anchored rock mass from deeper damage. The research results have important theoretical and guiding significance for design of bolt anchorage systems under blast load.