Numerical investigation of the scale effect and anisotropy in the strength and deformability of coal

The decrease in strength and stiffness of coal with increase in specimen size has long been recognized as scale effect. In this study, a synthetic rock mass (SRM) approach has been used to investigate this scale effect and the anisotropy of coal. A discrete fracture network (DFN) for the coal was created and then embedded into bonded-particle models to form a range of varying size of SRM coal specimens. Unconfined compression tests on the SRM specimens showed that the SRM approach is capable of quantitatively reproducing the dependency of the strength and stiffness on the size of the coal specimens. The strength and stiffness anisotropy of coal can also be reproduced. The numerical results are shown to be in good agreement with published laboratory and field test results.