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In a CO 2 storage project, CO 2 may be able to escape from channels caused by the formation's uplift, fault reactivation, and wellbore failure owing to overpressure build-up and likewise, coal excavation during which equilibrium disruption of stress could possibly lead to fl oor heave, roof collapse, and surface subsidence. When the carbon capture and storage (CCS) project and coal mining engineering activity occur in the same location, coal mining may also induce wellbore failure if the stope border is too close to the well. This is a real and challenging problem for CO 2 geological storage in the Ordos Basin in China. We consequently investigated four key problems for such a combination system. The main conclusions obtained from numerical simulations are as follows. (i) Permeability is the most important factor that affects the fl ow rate at the injection point and the reservoir pore pressure. (ii) The interfaces between the coal layers and their adjacent rocks are easy to damage the casing. Our work suggests that the coal pillar should be set aside at least 90 m to maintain the tensile strength of the casing below the designed value. (iii) No impact occurs to the caprock from coal mining; thus, a coal seam 440 m in depth could be excavated if the original caprock is intact and no complex geological structure exists in the location. (iv) Permeability is the most crucial factor affecting surface displacement, and CO 2 injection permits a surface displacement reduction of 0.04136 m compared with individual coal excavation.

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Previous experimental studies of anisotropy and non-coaxiality by using the hollow cylindrical apparatus are mainly focused on granular soils, which feature irregular particle shapes and non-uniform particle size distributions. This paper experimentally investigates these two characteristics on assemblages of particulate materials with regular particle shapes and uniform particle sizes. These assemblages are made from spherical, cylindrical and cubical particles, with an increasing order of particle angularity. Two types of loading paths in the hollow cylindrical apparatus are applied. One is the monotonic loading path with a range of fixed angles of major principal stress with respect to the horizontal bedding plan, used to investigate the anisotropy of materials. The other is the path of pure principal stress rotations, used to study the non-coaxiality. The experimental results indicate that these three materials exhibit a strong anisotropy and non-coaxiality. Their stress-strain responses are dependent on the orientation of major principal stress. The non-coaxiality is a function of stress ratio. In addition, there is a noticeable trend that these two characteristics are dependent on the angularity of particles. The more angular the particles are, the greater anisotropy and non-coaxiality take place.

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