Abstract
From the perspective of resource recovery and environmental protection, coal gangue-fly ash cemented backfill coal mining has become an important direction for the green development of coal mines in recent years. Analysis of the rheological parameters of backfill slurry is the basic principle to design a backfill pipeline system. Coal gangue-fly ash backfill slurry has a mass concentration of 76% to 79% and a maximum particle size 20 mm. Therefore, it is difficult to use conventional rheometers for experimental analyses of the rheological parameters of such fluids. We developed a rheometer for high-concentration coal gangue backfill slurry (HCGS rheometer) based on the coal gangue-fly ash backfill practice of Gonggeying Mine, and analyzed the rheological properties of the backfill slurry. The experimental results showed that the Reynolds number of the coal gangue-fly ash backfill slurry was much smaller than the critical Reynolds number, indicating the flow state in the pipeline was laminar. Based on these results, it may be more appropriate to control the mass concentration to 77% to 78%, and the suggested fly ash content is 25%. This work provides a scientific basis to optimize the backfill parameters and pipeline system in coal mines.
Highlights
IntroductionChina’s “three unders” (i.e., under buildings, water bodies, and roads) are estimated to host approximately 14 billion tons of coal
China’s “three unders” are estimated to host approximately 14 billion tons of coal
To extract coal found under water, the Gonggeying Coal Mine used coal gangue-fly ash cemented backfill for the pillars
Summary
China’s “three unders” (i.e., under buildings, water bodies, and roads) are estimated to host approximately 14 billion tons of coal. The backfill mining method is an effective approach to control mining subsidence and improve the resource recovery rate while extracting coal from the “three unders.”. This approach has become an important direction to support green coal mining in recent years [4,5,6,7,8]. The coal gangue-fly ash cemented backfill mining method uses cement, coal gangue, and fly ash to prepare a high-concentration backfill slurry that is transported underground through pipelines This approach can effectively control mining subsidence and improve the resource recovery rate while more fully utilizing the coal gangue and fly ash resources [11,12,13]. This paper explores and develops a high-concentration coal gangue backfill slurry rheometer (HCGS rheometer) and the corresponding rheological parameter testing methods
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