Deformation failure characteristics of coal-rock combined body under uniaxial compression: experimental and numerical investigations

The deformation and failure behaviour of coal-rock combined body under uniaxial compression were investigated experimentally and numerically. The mechanical parameters, including the uniaxial compressive strength (UCS), elastic modulus and full-scale stress-strain curves, were obtained. A detailed analysis of the evolution of the internal cracks based on X-ray computed tomography (CT) observations and acoustic emission (AE) locations is presented. The experimental results show that the mechanical properties and deformation failure characteristics of the coal-rock combined body were governed mainly by the coal. The UCS and elastic modulus of the coal-rock combined body were slightly larger than those of the coal and most of the cracks occurring in the coal were a result of the uniaxial compression. Furthermore, a numerical simulation was conducted to validate the experimental evidence. Finally, based on this understanding, a constitutive relationship was proposed using the natural strain described in Hooke's law for accurate modelling of the deformation of the coal-rock body. A good agreement was obtained between the numerical results and experimental data during the pre-peak regime.