Abstract
Spalling is a wave-induced dynamic fracture phenomenon. The waves can be either one: elastic, elasto-plastic, or shock waves. From a continuum mechanics point of view, fracture mechanics and wave propagation form the main ingredients in the formation of spalls. Recently, however, micro-structural effects have become important in the initial stages of spall formation in a variety of engineering materials ranging from metals to rock and concrete. From a structural geology point of view, the rock mass cannot be modelled as a continuum. In this case, a discontinuum approach has to be taken where the individual features of the rock mass such as joints and faults need to be taken into account. From an application point of view, spallation is important where rapid loading by explosives, impact, or energy deposition, occurs. The range of applications stretches from blasting in mining engineering to damage prevention to structures under explosive excitation.
This contribution offers a multi-faceted and multi-disciplinary approach to the study of spalling with special attention to analytical and experimental work. The reader is assumed to be somewhat familiar with the basics of continuum mechanics, fracture mechanics, and propagation of elastic, plastic and shock waves. The application to rock and concrete will show the effects of structural geological discontinuities such as open and closed joints – and to some degree also faulting – in rock, as well as the micro-structure of concrete on the (shock) wave field.
Extensive use will be made of time-space diagrams which proved very useful in practical applications to blasting problems [Rossmanith, H.P., 2002, The use of Lagrange diagrams in precise initiation blasting. Part I: two interacting blastholes, Fragblast 6, 104–136].
Acknowledgements
The authors kindly acknowledge the assistance in the graphical design by Mrs Alexandra Kühnelt-Leddinh in Vienna.