Mechanism and control technology of roadway floor heave deformation and failure under the influence of repeated mining in multiple coal seams.

Deformations caused by of roadway floor heave due to the repeated mining of multiple coal seams is a prominent problem in deep coal mining. This work examines roadway floor heave under the influence of repeated mining in multiple coal seams as the research object. Through theoretical analysis, numerical simulation, and field experiments, the failure mechanism of floor heave deformation is revealed, and effective control techniques are proposed. A deformation model for multiple-seam repeated mining was established based on the theory of elastic mechanics, and a control mechanism was analysed. An optimised treatment method for roadway floor heave was proposed. Displacement, stress, and failure zone analyses of the original support and optimised surrounding rock were conducted via FLAC software, and the optimal treatment method for roadway floor heave was obtained. The applicability of this support method was verified through onsite application. The results indicate that stress superposition is the cause attributed to the repeated mining of multiple coal seams, and stress reduction and effective roof support are the keys to preventing and controlling roadway floor heave. Compared with the original support method, the amount of floor heave was reduced by 60%, and the shrinkage of the two sides was also significantly reduced. The optimised roadway support method provides better control over floor heave.