ABSTRACT: Delay blasting has been practiced for several decades in mining and quarrying operations and is considered a mature technology, but with the advent of precision detonators capable of achieving delays in the order of microseconds, further research is required to assess the efficacy of using such precise delay times for common applications such as fragmentation and controlled excavation. For a preliminary assessment, we have simulated the explosives induced fracturing process using the Dynamic Lattice Network Model for processes involving varying delay times including simultaneous detonations.
The discrete model is composed of particles and springs with randomly assigned stiffnesses to reflect the material property variations and their influence on the initiation and propagation of fracture m rocks; moreover, the model is capable of simulating the different stages of fracture including crack branching. In the simulation, the springs are assumed to respond to explosive induced stresses in a linear elastic and brittle manner and the material response is expressed in terms of particle dislocations and spring elongations and compressions. Failure occurs when a spring is stretched or compressed beyond a randomly assigned ultimate limit which is based on the material's Ultimate strength in tension and compression. Upon failure, the stresses are dynamically redistributed and the fracture process is continued.
The emphasis of this modeling effort is on the study of the fracture phenomenon under dynamic loading, especially the extent of fracturing and branching, and the analysis of the influence of delay time in multiple hole blasting on fragmentation. Of particular interest is the stress wave interaction and its influence on the fracture propagation, and the resultant fracture pattern.
