Based on a self-developed shear-seepage coupling testing device for coal-rock

experimental tests were conducted on coal-rock specimens in the process of CO2 injection to investigate shear-seepage of coupled properties. Meanwhile

the sheared fracture surfaces from different normal stresses were scanned

and their characteristics were analysed through two-dimensional (2D) and three-dimensional (3D) statistical parameters. The results show that the shear failure of coal-rock specimen is mainly plastic damage under the condition of constant gas pressure. With the increase of normal stress

the peak shear stress of coal-rock increases as well

and the peak shear stress and normal stress of coal-rock approximate a linear relationship. The normal stress is one of the influence factors of sheared fracture surface characteristics. Under the condition of constant gas pressure

when the normal stress increased

2D and 3D statistical parameters generally showed a trend of decrease

in other words

the sheared fracture roughness and prominence of the coal-rock decreased with the increase of normal stress. Through analysis on coal-rock shearing process

the normal stress can affect the shape and seepage characteristics of sheared fracture surface of the specimen by influencing the extension area of the shear crack.