Abstract
Fly ash cement is used to solidify marine clay to prepare marine-clay-based cemented paste backfill (MCCPB) to fill the underground goaf of mines, which not only utilizes solid waste such as fly ash and marine clay, but also controls surface subsidence and protects the environment. To simulate the complex underground mine water environment of the filling body, a dry-wet cycle aquatic environment test under different material ratios and curing ages was designed. The water absorption and unconfined compression strength (UCS) of MCCPB with curing ages of 7 and 28 days under the action of 0, 1, 3, and 7 dry-wet cycles were investigated. The results indicate as the number of dry-wet cycles increases, the surface of MCCPB becomes significantly rougher, and the water content and the solid mass decrease accordingly. Different ratios and curing ages of MCCPB in dry-wet cycles of the UCS tend first to increase, then decrease. Meanwhile, the stress-strain curve of the specimen shows that the trend in the elastic modulus is consistent with that of UCS (first increasing, then decreasing), and that, the minimum UCS value of the specimen still meets the early strength requirements of cemented paste backfill in coal mine geothermal utilization. On the one hand, it proves the feasibility of fly ash cement-solidified marine clay for use as cemented paste backfill in coal mines; on the other hand, it also expands the available range of cemented paste backfill materials in coal mines.
Highlights
Cemented filling mining technology involves mixing mine solid waste, additives and water to prepare high-concentration cemented slurry without dehydration and pump the slurry to the underground goaf of the mine through a filling pump area, establishing a system for filling the underground mining space of mines
There is no obvious change in the surface of fly ash cement-treated marine clay after one dry-wet cycle; after three cycles, the surface of the specimen began to become rough
There was no significant crack and surface peeling during the process of dry-wet cycling
Summary
Cemented filling mining technology involves mixing mine solid waste (fly ash, tailings, construction waste, etc.), additives and water to prepare high-concentration cemented slurry without dehydration and pump the slurry to the underground goaf of the mine through a filling pump area, establishing a system for filling the underground mining space of mines. This technique has been widely applied in the global mining industry [1,2]. The cemented filling technique alleviates high in-situ stress in deep mining, and controls the surface subsidence, improving the safety and efficient production of underground operation, and makes harmless and safe and effective use of solid waste resources, which has become an important part of green mining technology [9,10]
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