To achieve high-quality development of the coal industry, a series of longwall panels with ultra-large cutting heights (8–10 m) have been developed in China. In such panels, mined-out space increases quickly. The mining influence range is large and mining disturbance is intense, resulting in severe strata behavior and threatening mining safety at the working face. For improving roof supporting effectiveness in such longwall panels, No.122104 longwall panel in Caojiatan Coal Mine is selected as the engineering case. Thick-hard strata movement characteristics, roof structure model, roof instability mechanism and support resistance determination method in longwall panel with ultra-large cutting height are analyzed with theoretical analysis, laboratory test and field measurement, helping to select the strata needing hydraulic fracturing. The results show that thick-hard strata undergo simultaneous shear rupture in longwall panels with ultra-large cutting heights. The fractured blocks exhibit large rotation angles due to the large cutting height, forming roof rotating blocks with large height-to-span ratios above the supports. The high-level thick-hard strata undergo shear rupture, free falling, rotational motion and punching rupture under the support of roof rotating blocks, forming a composite roof structure consisting of high-level punching beams and roof rotating blocks. Shear rupture mechanisms is revealed for the thick-hard strata. Mechanical conditions for the stability of rotating block and punching rupture of thick-hard strata are derived. Determination method for the punching force is proposed. The punching rupture of high-level roof strata is identified as a critical cause of multiple dynamic loads. Both lower frictional effect and high-level punching effect are considered, support force calculation model is established under the composite structure. Zonal hydraulic fracturing technique serves as an effective method for weakening the strong mining pressure. Identification principle is given for the fracturing level. The strata prone to punching rupture are identified as the targets for hydraulic fracturing. The fracturing range is also determined for the overburden strata based on the developed model. After fracturing, the strength of the thick-hard roof is weakened. Elastic strain energy stored in the roof is reduced. Thus, the number and energy of mining-induced micro-seismic events are dropped. The bedding separation fracture developed in the overburden is increased. The failure mode of fractured strata transits from shear to tension type. Support force decreases by 11.5%. The results may provide guidance for support selecting and regional hydraulic fracturing in longwall face with ultra-large cutting height and thick-hard strata.
Against the backdrop of the “dual carbon” goals, the mineralization and sequestration of CO2 from solid waste is a key approach to simultaneously advancing the resource utilization of solid waste and CO2 sequestration. However, there has been a lack of systematic assessment of the mineralization and sequestration potential of multi-source solid waste from coal production bases and the regional variations therein. To address the needs for resource utilization and carbon sequestration of typical solid waste in coal-producing regions, a method for assessing the potential of solid waste mineralization and CO2 sequestration was developed. The theoretical upper limits for carbon sequestration capacity of different types of solid waste were estimated, and regional sequestration potential was quantified. Through analysis of mineral composition and chemical characteristics, the mineral composition basis of typical solid waste and differences in their reactivity were revealed. The results indicate that solid waste derived from raw coal exhibits relatively low mineralization reactivity and requires activation pretreatment to enhance mineralization efficiency. In contrast, solid waste derived from modified coal and certain metallurgical solid wastes possess high mineralization potential and can serve as highly efficient substrates for mineralization reactions. Building on this, the theoretical carbon sequestration capacity of various solid wastes was calculated based on their mineral composition and stoichiometric relationships; a model for assessing mineralization sequestration potential was established; and CO2 sequestration potential was estimated in conjunction with regional solid waste generation volumes. We further analyzed the effects of feedstock composition, reaction conditions, environmental factors, and equipment performance on mineralization efficiency; proposed the technical approach of “sequestering carbon with waste, treating waste with carbon, and backfill waste with air”; identified technical directions for multi-pathway synergy; and analyzed the main challenges facing large-scale application in terms of feedstock suitability, high-efficiency mineralization reactors, and policy standards. Through systematic elucidation of solid waste mineralogy and quantitative assessment of mineralization sequestration potential, this study provides a scientifically grounded evaluation methodology, with the aim of offering theoretical support and technical reference for promoting large-scale solid waste utilization and efficient CO2 sequestration in coal mining bases.
Drawing on strategic research projects of the Chinese Academy of Engineering, national energy policy documents, publicly available industry statistics, and information on representative projects, the policy logic and evolving connotations of China’s energy system are systematically reviewed, from a stable, economical, clean, and secure energy supply system, through a clean, low-carbon, secure, and efficient modern energy system, to a new energy system characterized by security and efficiency, clean and low-carbon development, multi-dimensional coordination and collaboration, and intelligence and inclusiveness. The strategic role of the modern coal chemical industry is assessed in terms of energy security, feedstock substitution, industrial-chain resilience, and low-carbon transition. The results show that China has established a relatively complete industrial base and an independently developed technology system for the modern coal chemical industry. Major routes, including direct and indirect coal liquefaction, coal-to-natural gas, coal-to-ethylene glycol, and coal-to-olefins, have achieved commercial operation. In 2025, these major routes produced approximately 36 million tonnes of products and converted approximately 130 million tonnes of standard coal, indicating that the industry has progressed from demonstration and exploration to a stage of coordinated scale-up, high-end development, and low-carbon transition. Nevertheless, major constraints remain, including high carbon-emission intensity, severe water-resource constraints, intensifying homogeneous competition in basic products, and insufficient alignment between project siting and ecological carrying capacity. During the 15th Five-Year Plan period and over the medium to long term, development should not continue to rely primarily on capacity expansion. Instead, clean and efficient coal conversion should provide the foundation for coordinated advances in the iterative upgrading of key clean and low-carbon technologies, green hydrogen coupling and multi-energy complementarity, differentiated high-end products, intelligent process control, park-level coordinated energy-carbon-water optimization, and life-cycle carbon- and water-footprint management. These measures would support a modern industrial system that balances energy security, industrial-chain security, economic viability, and China’s carbon-peaking and carbon-neutrality goals.
Land reclamation using coal gangue is an important approach to the large-scale disposal of coal-based solid wastes and the ecological restoration of mining land. However, existing reclamation technologies focus mainly on coal gangue backfilling and soil covering and are inadequate to ensure the structural stability of the backfill, control the risks of spontaneous combustion and heavy metal leaching and release, and support subsequent vegetation restoration. An environmentally safe coal gangue land reclamation technology based on solidified soil grouting is developed, with a focus on the regulation of solidified soil slurry, reconstruction of the internal structure of the coal gangue backfill, and the resulting environmental functions. In situ soil from the mining area is used as the principal material, cement and coal-based solid wastes are used as cementitious materials, and functional admixtures are incorporated to prepare an injectable solidified soil slurry. The prepared slurry is injected through boreholes into the interparticle pores of the coal gangue backfill. After hardening, the slurry is integrated with the gangue skeleton to form a reconstructed solidified soil-coal gangue subsoil layer characterized by pore filling and particle cementation. Functional evaluation of the reconstructed subsoil layer shows that macropores between gangue particles are blocked, thereby impeding continuous oxygen transport. The transition of heated coal gangue from the endothermic stage to the exothermic oxidation stage is also delayed. Oxygen-barrier and flame-retardant functions are thus achieved through restricted oxygen supply and delayed thermal reactions. Meanwhile, the solidified soil filling phase and hydration products reduce contact between infiltrating water and reactive gangue surfaces through interfacial coating, pore blocking, adsorption, and immobilization. Consequently, the migration and release of Pb, As, and Zn are inhibited, and the proportion of labile heavy metal fractions is reduced. During two consecutive years of post-reclamation engineering monitoring, no persistent leachate, spontaneous combustion caused by coal gangue oxidation, or surface soil contamination is observed in the demonstration area. The major monitored groundwater parameters meet the Class Ⅲ groundwater quality limits, the internal temperature of the reconstructed subsoil layer remains below 20 °C, and vegetation on the platform and slopes is restored. The engineering applicability of this technology for large-scale coal gangue disposal, environmental risk control, and vegetation restoration following soil covering is validated by these results. A technical pathway is thereby provided for shifting coal gangue management from stockpiling to functional and environmentally safe land reclamation.
Coal mining generates large volumes of mine water and coal gangue, both of which pose significant challenges due to their massive output, low resource recovery rates, and potential to cause ecological damage and environmental pollution if improperly managed. These issues have become persistent obstacles to the green development of the coal industry. Addressing these problems, this paper focuses on establishing a key pathway for the graded, quality-based treatment and systematic ecological utilization of mine water and coal gangue. Based on practical needs for water conservation, solid waste disposal, and ecological restoration in mining areas, it systematically analyzes the interrelationships among treatment, utilization, and ecological integration of mine water and coal gangue. For mine water, the study clarifies an integrated protection and systematic ecological utilization pathway that includes source protection, underground water storage, classified treatment, and multi-scenario ecological applications, emphasizing full-process management from source to end use and tiered, quality-based utilization. For coal gangue, it identifies critical pathways for graded and quality-based treatment and ecological utilization, including source reduction, underground backfilling, production of building materials, land reclamation, and green storage, promoting a shift from single disposal to resource-oriented and functional utilization.Building upon the cascading reuse of mine water and the classification-based utilization of coal gangue, the paper further integrates application scenarios such as underground backfilling, surface soil improvement, and vegetation restoration. This integration promotes synergy between water recycling, safe solid waste disposal, and enhanced ecological functions in mining areas, forming a coordinated governance pathway for mine water and coal gangue that supports systematic ecological restoration. This approach enables the integration of mine water and coal gangue management into the broader ecological restoration process, ensuring mutual reinforcement among water recycling, safe waste disposal, and ecological enhancement, thereby providing technical guidance and practical reference for resolving the challenges associated with mine water and coal gangue management in the coal industry.
