Cemented backfilling mining technology with continuous mining and continuous backfilling method for underground coal mine and typical engineering cases

To solve the problems of high cost of cemented backfilling mining, complex backfilling technology and prominent contradiction between mining and backfilling in underground coal mine, the continuous mining and continuous backfilling technology was proposed, which can realize the parallel operation of mining and backfilling. The flow characteristics and age strength of backfilling materials with different proportions were investigated. Additionally, the underground mixing and surface mixed transportation system of backfilling slurry suitable for different coal seam inclinations and the corresponding dense filling methods of working facewere put forward, forming a complete set of cemented backfilling mining technology with continuous mining and continuous backfilling method. Thedynamic migration law of stress in surrounding rock of stope inthe process of backfilling mining was studied under the influence of different backfilling mining modes. Based on the characteristics of “the amount of roof-to-floor convergence before backfilling, the displacement between the backfilling body and the roof, and the amount of compression of backfilling body” which affect the surrounding rock deformation of the backfilling stope, a triple-control strategy of overburden movement in backfilling stope was adopted.The strategy is composed of a faster filling speed, a reasonable filling degree of goaf and suitable strength of filling body. Therefore, the mechanism of alternating load and roof control of coal pillar and backfilling body was explained, andthe technical principle of replacing coal step by step through continuous mining and continuous backfilling was also revealed. The application found that the alternating load of coal pillar and backfilling body to control the roof can ensure a stable backfilling space.The step-by-step replacement of coal pillar can ensure that the backfilling material with a reasonable curing time, realizing that coal mining and backfilling donot interrupt with each other. Therefore, the working face can realize continuous mining and continuous backfilling, ensuring the maximum parallel operation of mining and backfilling, and then greatly improve the efficiency of cementedbackfilling mining. The research results have been applied to four coal mines in western Inner Mongolia for different application cases, i.e., mining under the ecological park, composite roof, treatment of solid waste and recovery of protective coal pillars ofmain roadways. The field tests show that cemented backfilling mining technology with continuous mining and continuous backfillingmethod has achieved some good engineering application results infourcoalmines, which can effectively control strata movement, and efficiently replace the remaining coal resources.