International Journal of Rock Mechanics & Mining Sciences 45 (2008) 111–121 Numerical investigation of blasting-induced damage in cylindrical rocks Zheming Zhu a,Ã , Heping Xie a , Bibhu Mohanty b a College of Architecture and Environment, Sichuan University, Chengdu, Sichuan, 610065 China b Department of Civil Engineering, University of Toronto, Toronto, ON, Canada M5S 1A4 Received 6 November 2006; received in revised form 29 March 2007; accepted 27 April 2007 Available online 16 July 2007 Abstract In order to investigate rock fracture and fragmentation mechanisms under dynamic loading, a cylindrical rock model with a centralized borehole is developed through the use of AUTODYN code. According to the material properties and loading conditions, four kinds of equation of state (EOS), linear, shock, compaction and ideal gas, are applied to the four kinds of materials employed in this numerical model. A modified principal stress failure criterion is applied to determining material status, and a well-behaved explosive, PETN, and a relatively homogeneous igneous rock, diorite, are used in this rock model. A single centrally located line source of explosive is fired numerically to produce the dynamic loadings operating on the surrounding rocks. This numerical model is applied to actual blasting conditions. The rock failure mechanism under dynamic loading is first analyzed, and then the influences of the following factors on rock fracturing are discussed: (a) coupling medium, (b) confinement, (c) boundary condition, (d) initiation location in an explosive column, and (e) air ducking. The results show that all these factors have significant effects on rock fracturing under dynamic loading. r 2007 Elsevier Ltd. All rights reserved. Keywords: Dynamic fracture; Blasting; Numerical model; Stress wave; Crack propagation 1. Introduction Blasting of large masses of rock in mining and quarrying is a complex process. The efficiency of such operations depends on the knowledge of the detonation properties of the explosive and the response of the surrounding rock mass. This is because the processes of rock fracture and fragmentation around a borehole are strongly dependent on the parameters of the detonation and the dynamic response of the rock, as demonstrated in field experiments [1–3] and in bench-scale experiments [4]. The detonation properties of the explosive consist of the explosion pressure, its time history, and the total energy delivered to the rock. The response of the rock mass to such time- varying high-amplitude stresses is even more complex, as all the relevant strain-rate-dependent properties of the subject rock are not known. Under this scenario, it is essential to implement both experimental study and numerical study. The experimental study could generate an experimental database, and the numerical study could simulate the processes of rock fracture and fragmentation through the use of numerical models so as to obtain a better understanding of the dominant parameters that control blast results. Grady and Kipp [5] applied a fracture model coupled with a material description for stress wave propagation to predict quantitatively fracture and fragmentation under explosive loading conditions. Stecher and Fourney [6] used a model that joins an energy release rate versus crack velocity fracture criterion with a two-dimensional finite difference computer program to predict the propagation of a crack that is initiated and driven by an explosive loading. Nilson et al. [7] developed a computational model to predict the propagation of gas-driven fractures emanating from a pressurized borehole, and their calculation of peak pressure, pressure-decay time, and fracture extent are in good agreement with several sets data from the propellant- driven field experiments. In order to simulate the flying distance, muckpile and damage of remaining rock mass in blasting operations, Munjiza and Owen [8] developed a discrete element model for rock blasting. In their model, ARTICLE IN PRESS www.elsevier.com/locate/ijrmms 1365-1609/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijrmms.2007.04.012 Ã Corresponding author. Tel: +86 13568967156. E-mail address: zhemingzhu@hotmail.com (Z. Zhu).