Effects of bedding on the dynamic indirect tensile strength of coal: Laboratory experiments and numerical simulation

Abstract

Dynamic indirect tensile tests were carried out by using a Split Hopkinson Pressure Bar (SHPB) for coal sampled from the Datong mine in China. The principal purpose was to explore the influence of bedding structure in the coal on its dynamic indirect tensile strength. However, to resolve some contradictions, X-ray micro CT, high speed optical imaging and a discrete element based modelling approach were combined to analyze the test results. The X-ray micro CT was used to detect the actual bedding structure in the coal; the high speed imaging captured failure patterns of the specimens with different bedding directions; and the numerical modelling was utilized to investigate the influence of different bedding structures on dynamic strength. The SHPB and numerical results illustrate that dynamic indirect tensile strength reliably correlates with impact velocity. In addition, the dynamic indirect tensile strength is not only influenced by the bedding direction but also by the roughness and discontinuity of the bedding. Based on these findings, a method is developed to further process the test data including a model to describe the dynamic indirect tensile strength of Datong coal.