DEM simulation of mechanical behavior of jointed coal in large scale under uniaxial compression

To investigate the influence of joints on uniaxial compression behavior of jointed coal,the synthetic coal mass specimen was first constructed based on the in-situ measurement of joints and numerical parameters calibration tests. Then the numerical uniaxial compression tests on intact coal and jointed coal with REV size under different load-ing orientations were conducted. Finally,the influence mechanism of joints on the mechanical behavior of jointed coal and the fracture formation mechanism were analyzed. The study shows that:① The constructed synthetic coal mass model can represent the jointed coal investigated,with the REV equaling to 1. 0 m×1. 0 m×2. 0 m. ② Joints weaken the UCS and elastic modulus,but increase the deformation of jointed coal under uniaxial compression,with the weake-ning / increasing degree depending on the relation between loading orientations and joints. ③ Joints determine the fail-ure mode of jointed coal under uniaxial compression. The jointed coal by splitting fracture parallel to loading directions,with different splitting geometries under different loading orientations. ④ The contribution ratio of matrix failure and the contribution ratio of joints activation were put forward,which can be used to quantitatively evaluate the contri-bution degree of matrix failure and joints activation to the failure of jointed rock,respectively. ⑤ The joint parallel to loading orientation is converted to activated pre-existing fracture under the effect of loading force,from the end of which grow the wing crack,both of which form the compression-induced tension fracture composition. For jointed coal containing non-penetrating joints,the splitting fractures are formed by the coalescence of fracture compositions. For the coal mass containing through joints,the splitting fractures are formed only by the through activated pre-existing frac-tures.