The Development and Application of Shortwall Backfill Mining with Tailing Paste: A Case Study in China Mine

Baoliang Zhang, Changqing Ma, Yongsheng Zhao, Dandan Liu

Abstract


Cemented paste backfill (CPB), a mixture of tailings, water and cement powder, has been extensively used in underground mining worldwide for the purpose of ground support and tailings disposal, and it is also often used in longwall mining. However, there is no intermittent time for longwall backfill mining, which increases the risk of surface subsidence, buildings damage and rail fracture, and large reserves of coal resources cannot be mined using the conventional longwall mining method. Therefore, the development of a new mining method applicable to buildings, railways or water bodies has been a major concern. Meanwhile, lots of tailings produced during the mining process may despoil large-scale land and cause a great deal of pollution. Backfill mining using tailings can be an alternative method, which not only limits roof subsidence, but also minimizes the need of surface disposal through a full utilization of the solid waste. A new technology of shortwall backfill mining with tailing paste is developed, which includes the tailings screening system, mixing system, pumping and pipeline delivery system and working face isolation system. Factors such as backfill strength, liquidity and costs were fully taken into account during the process of designing tests, and the optimal combination was achieved when the silt ratio was 1:5 and the mass solid concentration was 70%. The technology was further tested in Zhangzhao coal mine 102 mining area. The coal recovery rate was more than 85% and treated 500 thousand tons of tailings. The roof did not break, and the maximum value of surface subsidence was 240mm when shortwall backfill mining technology with tailing paste was applied. Also, no deformation or destruction of the buildings was detected. Therefore, this low-lost technology has achieved four goals: the release of coal resources, the control of surface subsidence, the protection of buildings and the effective treatment of solid waste.


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