Meso- and macro-behaviour of coal rock: observations and constitutive model development

Mesoscopic structures must be determined in order to analyse the behaviour of inhomogeneous materials such as coal rock. In this study, a three-dimensional texture of coal rock is scanned by X-ray tomography images using CT system. The time-dependent fracturing behaviour of coal rock for dynamic damage test is then observed by mesoscope under uniaxial stress conditions. In order to determine the dynamic damage evolution process of coal rock, a meso-damage model is introduced, and a constitutive relationship is developed for coal rock subjected to dynamic uniaxial compression in three stages including (I) quasi-linear phase, (II) damage evolution stage and (III) damage accelerating fracture extension. The corresponding meso-mechanical damage mechanisms are investigated.