Deep coal fluidized loop-shredded mining technology and the in-situ mining mechanical behavior of coal

Deep coal fluidized mining is a disruptive technology for overcoming the depth limits of coal extraction. To achieve the industrial goal of deep coal fluidized mining—“no coal on the surface, no personnel underground”—traditional roadway layouts, mining methods, and hoisting‑transportation systems must be transformed. Accordingly, this study proposes an innovative deep coal fluidized loop-shredded mining (FLSM) concept, which resembles the hand‑tearing bread method. Using the central shaft of the coal seam block as the geometric center, intelligent mining equipment extracts coal sequentially from the outer ring toward the inner ring of the mining area. The proposed FLSM method integrates deep in-situ shield mining, crushing and separation, in-situ liquefaction, electrification, gasification, and in-situ negative-carbon backfilling. Considering the spatial geometric characteristics and structural features of the overlying strata under FLSM, a T-shaped mechanical model was established. An analytical solution for coal-rock stress, accounting for depth effects and the disturbance characteristics of the FLSM, was developed to support in-situ environmental simulation and testing. Based on the in-situ geo-stress environment, a numerical analysis model was constructed to analyze the spatiotemporal evolution of coal samples plastic zones and mining-induced stress under different coal pillar widths. As loop-shredded mining advances from the outer to the inner ring, vertical stress undergoes dynamic transfer, and the central coal pillar becomes a zone of high stress concentration. Laboratory measurements confirmed that peak deviatoric stress under FLSM is reduced by 38.6%, 30.6%, and 22.6%, respectively, compared with non-pillar mining, top coal caving mining, and protective seam mining.