On the nature of energy-horizon and determination of length scales in dynamic fragmentation of rocks

Grady's energy-horizon theory of dynamic fragmentation (EHTDF) is reviewed. The energy-horizon essence is explored, and a new approach for determining the related dynamic fragmentation length scales is proposed. It is shown that energy-horizon is the effective size of the equivalent sample covered by dynamic disturbance, and the lower energy-equilibrium failure criterion in Grady's EHTDF may be replaced by static size effect law, with the upper bounding failure criterion curve used instead of the energy-based criterion. The length scales in Grady's EHTDF can be determined by combining the energy-based criterion and static size effect law with the relation between dynamic strength, strain rate, and fragment size obtained from the Maxwell model of rock deformation and fracture. Comparison of the theoretically predicted and the experimentally measured values of length scales in dynamic fragmentation of rock shows the validity of the proposed approach.

Automated summary

Grady's energy-horizon theory of dynamic fragmentation (EHTDF) is reviewed and a new approach for determining the related dynamic fragmentation length scales is proposed. The study combines energy-based criteria and static size effect law with the relation between dynamic strength, strain rate, and fragment size obtained from the Maxwell model of rock deformation and fracture. The comparison between theoretical predictions and experimental measurements validates the proposed approach.