Numerical Study on Fracturing Process in Rock by Blasting a Cylindrical Charge

In blasting, cylindrical charge is generally applied in terms of energy efficiency. The dynamic fracturing in rock due to detonation of high-explosive involves quite fast process and extremely complex fracturing pattern. In addition, detailed fracturing process is generally not observable. Thus, blasting design tends to be based on empirical knowledge or law. It is also well known that fracturing process envisioned here depends on the applied pressure wave forms characterized by such as detonation property and amount of applied explosive. These in turn make the design optimization of blasting quite difficult and, even for the simplest blasting problem with a single free face, the fracturing mechanism has not been clarified yet. Therefore, it is of paramount importance to investigate the fracturing process due to blasting in detail for various types of applied pressure wave forms. For this purpose, application of numerical simulation is one of the most promising approaches. This paper proposed a method for the simulation of dynamic fracturing process through axisymmetric finite element formulation in which the initiation, propagation, branching and coalescence of fractures in heterogeneous rock can be analyzed. In particular, blasting a cylindrical charge through bottom priming in a cylindrical rock specimen was analyzed considering the difference of load configuration characterized by length of applied explosive. It was clarified that the resultant fracturing patterns were strongly dependent on the length of applied explosive. In addition, cross-shaped fractures occurring on the free face were successfully simulated by the proposed method, which were observed in the field-scale blasting with a cylindrical charge. Therefore, the applicability of the proposed method was validated and it can give a deep insight for understanding the dynamic fracturing process in rock due to blasting with a cylindrical charge.