Schematic diagram of the technical process for the experiment.

(a) Compression and restoration on the rock samples. (b) 3D view of a device for sample restoration, where the height, inner diameter, and outer diameter for the restoration holder are 110, 60, and 70 mm, respectively. The thickness and diameter of the pedestal are 10 and 110 mm, and the depth of the concave slot is 3 mm, which is consistent with the lower sealing washer. (c) Practical experimental routine for coal, sandstone, and mudstone. The volume ratio between the resin and catalyst is 1, the pressure of the high-pressure air is 2.0 MPa, and the inner wall of the restoration holder is evenly coated with Vaseline to facilitate the demolding process.