Research status and development trend of solid waste backfill in metal mines

In China, solid waste backfill technology has been used in metal mines for more than half a century. It has been essential for comprehensive excavation and utilization of mineral resources, environmental protection, and engineering safety. The core concept of solid waste filling has not changed qualitatively despite the rapid development of mining technology from semi-mechanized and mechanized automation and intelligence. It is mainly used in mine tailings, waste rock, and other solid wastes to control the hazards of goaf and tailings reservoir from the source to treat waste and hazards. However, the quality requirements, degree of fine control, and intelligent allocation technology of solid waste filling are undergoing considerable changes. Furthermore, the design philosophy of modern backfill technology consider comprehensive realization of solid waste utilization, environment conservation, mined-out area disposal, resource recovery, and ground pressure control that require optimal backfill method, sufficient mechanical strength, and pumpable backfill slurry, using information technology, automatic technology, and equipment technology. Besides, new backfill concepts are introduced, such as collaborative paste and multimaterial, synchronous, and functional backfills. In this paper, the framework of backfill mechanics was described, relying on rheology and solid mechanics. The influences of in-situ multifield factors were analyzed based on the characteristics of the in-situ stope, introducing the latest multifield coupling monitoring system. More details about the development trend and research status of critical processes in the backfill, including deep thickening, mixing, and long-distance pipe transport, have been updated. We propose a picture for the future development of intelligent backfill based on the advantages of intelligent backfill and performance of intelligent algorithms in the backfill field. In terms of the future trend of solid waste backfill, we feel that it can enrich green mining, explore the realization of modular, scale, and intelligent backfill, and actively examine and serve the needs of deep mining. Thus, the backfill method appears as the optimal choice for deep mining and green mining.