Numerical studies of rock fragmentation

The dynamic fracture process in rock has been modelled as a continuous accrual of damage, where the damage is defined to be the volume fraction of material that has been stress relieved by multiple crack growth. A rate equation, governing the growth of the damage, has been formulated based upon a microstructural analysis of crack growth rates and Weibull crack distribution concepts. For a prescribed tensile loading history, damage levels and fragment sizes can be obtained. In most geometries of explosive applications, there are large spatial variations in loading histories which lead to a variation in fragment sizes. Using a two-dimensional finite-difference wave-propagation code and fracture parameters for oil shale, calculations of several configurations of explosives illustrate the resulting damage to surrounding rock.