Coal strength measurement by stereo digital image correlation

Correct estimation of coal mechanical properties, including Young's modulus and Poisson's ratio, play a crucial role in on-site coal mining design and numerical simulations of coal behaviour. Traditionally, these parameters are determined through laboratory testing of cylindrical samples using strain gauges. However, such methods have limitations due to the potential errors from strain gauge misplacement, localised measurements at the gauge placement area, and difficulty in preparing a standard-size sample from coal. To overcome these challenges, this paper assesses the applicability of the Digital Image Correlation (DIC) technique on Brazilian-sized disc-shape coal specimens. Several benchmark tests were first conducted under uniaxial compression conditions at varying loading rates to verify the technique with known materials. While more verification tests need to be conducted to account for coal intrinsic heterogeneity, the conducted trials provide promising results and demonstrate that 3D DIC of Brazilian coal samples is a simpler yet effective method for determining coal Young's modulus and Poisson's ratio.