Shock wave response of window rock coal

Abstract

Shock compression measurements on a subbituminous coal from the Window Rock, Arizona area are presented. Measurements of this type are required for investigation of the effectiveness of various rubblizing or fragmentation techniques using explosives in preparation for in situ coal gasification. The results of this investigation, which demonstrate the feasibility of acquiring such data, show that this coal is a highly compressible material with the order of 6 per cent porosity in the form of macroscopic collapsible voids. Wave shapes were square (propagation with the wave front parallel to bedding planes) with only very slight evidence of elastic precursors. Comparison of the dynamic stress-strain results with static stress-strain curves shows that the deformation of coal is highly strain-rate sensitive. Finally, the significance of these observations are explored in terms of a hypothetical fragmentation situation. A wave propagation computer code was used to predict what happens when liquid explosive in a thin crack is detonated to produce shock loading of various materials.