Solid-gas coupling coal-like materials are essential for simulating coal and gas outbursts and the long-term safety study of CO₂ sequestration in coal. However, reported materials still differ substantially from natural coal in mechanical, deformation and gaseous properties; the latter two aspects are common not considered. There is a lack of a definite and quantitative preparation method of coal-like materials with high similarity for future reference. Here, 25 groups of raw material ratios were designed in the orthogonal experiment using uniaxial compression, shearing and adsorption/desorption tests. Experiment results indicated that the coal-like materials were highly similar to soft coals in properties mentioned above. And range analysis revealed the key influencing factors of each mechanical index. The gypsum/petrolatum ratio controls the density, compressive strength, elastic modulus, cohesion and deformation characteristic. The coarse/fine coal powder (1–2 and 0–0.5 mm) controls the internal friction angle and is the secondary controlling factor for compressive strength and elastic modulus. The effect of coal particle size on the sample strength was studied using scanning electron microscope (SEM). When the gypsum/petrolatum ratio increased, the deformation characteristics changed from ductile to brittle. The different failure modes in the samples were revealed. The coal powder content is a key in the gas adsorption/desorption properties and an empirical formula for estimating the adsorption capacity was established. Based on the range analysis of experimental results, a multiple linear regression model of the mechanical parameters and their key influencing factors was obtained. Finally, a composition closely resembling the natural coal was determined, which differs by only 0.47–7.41% in all parameters except porosity (11.76%). Possible improvements and extension to similar materials are discussed. The findings of this study can help for better understanding of coal and gas outburst mechanism and stability of CO₂ sequestration in soft coal seams.

Zonal disintegration, a phenomenon of fractured zones and intact zones distributed alternately in deep rock mass, is different from the excavation‐damaged zone of shallow rock mass. In this study, bonded block model of 3DEC was employed to study the fracture mode and origination condition of zonal disintegration. Initiation, propagation, and coalescence progress of fracture around the roadway boundary under different triaxial stress conditions are elaborated. Numerical simulation demonstrated that zonal disintegration may occur when the direction of maximum principal stress is parallel to the roadway axis. It is interesting to find that the fracture around the roadway boundary traced the line of a spiral line, while slip‐line fractures distributed apart from the roadway boundary. The extent of the alternate fracture zone decreased as the confining pressure increased, and alternate fracture zone was no longer in existence when the confining pressure reaches a certain value. Effects of roadway shape on zonal disintegration were also studied, and the results indicated that the curvature of the fracture track line tends to be equal to the roadway boundary in shallow surrounding rock of the roadway, while the fractures in deep surrounding rock seems unaffected by the roadway shape. Those findings are of great significance to support design of deep underground openings.

The strength and failure of rock masses are ambiguous due to their complex structure. Investigating the strength and failure of jointed rock mass remains a persistent concern in mining engineering. This study aims to investigate the effects of joint dip angles of complex discrete joints on the mechanical properties and fracture evolution of rock‐like material. Rock‐like specimens with complex joints were prepared using 3D printing technology and then tested under uniaxial compression loading. The experimental results reveal the following findings: (1) The anisotropy of rock‐like material with complex joints is lower compared to the rock‐like material with simple joints. (2) The ratio of long‐term strength to uniaxial compressive strength of rock‐like material remains consistent despite changes in the dip angle of the joints. (3) Differing from intact rocks, AE events of the rock‐like material with complex joints are obvious in the initial loading stage and elastic deformation stage. (4) When the dip angle of the joint sets is 0 and 90°, fractures progressively propagate, and the failure mode of the rock‐like material demonstrates tensile failure along the pre‐existing joints. Conversely, when the dip angle of the joint sets is 45° and 135°, fractures are simultaneously initiated at various locations within the rock‐like specimen, resulting in a failure mode of rotational failure by the newly generated block.