Study And Application Of CO₂ Mineralized Solid Waste Backfill Materials For Water Retention Mining In Hanglaiwan Coal Mine

To address the problem of water resource loss during coal mining in Hanglaiwan Coal Mine,we explored and developed CO₂ mineralized coal-based solid waste backfilling materials（CMWB）to control overlying strata damage and deformation and achieve water retention mining.We analyzed the mechanical properties,rheological characteristics,microstructure,phase characterization,and carbon fixation efficiency of CMWB and investigated its strengthening properties.With Hanglaiwan Coal Mine as the research background,we conducted exploratory research on the engineering practice of CMWB,providing a theoretical basis and reference for the future application of CMWB in water retention mining.The main research results are as follows:（1）Using the fly ash from a nearby power plant near the Hanglaiwan Coal Mine as aggregate and cement,CO₂ gas,and silicate additives as auxiliary materials,the development of CMWB was explored.The key ratio optimization determination method of CMWB was proposed,and exploratory research was conducted on its application in the Hanglaiwan coal mine.（2）The rheological and working characteristics of CMWB were studied to clarify its applicability underground.The Herschel-Bulkley model fitting curve of CMWB shear stress and shear rate was analyzed,and the thixotropic hysteresis curves of different ratios of CMWB slurry under different shear rates were determined.The influence of fly ash content on the slump of CMWB was explored,and the control effect of fly ash content on the initial and final setting time of CMWB was revealed.The uniaxial compressive strength（UCS）of CMWB under different age and fly ash content conditions was obtained.The research results show that adding CO₂ gas can significantly improve the rheological properties and strength of the filling material,making it exhibit better flowability and stability in engineering applications.（3）The microstructure and mechanical strengthening mechanism of CMWB were studied.The phase characterization and microstructure of CMWB were revealed through X-ray diffraction（XRD）and scanning electron microscopy（SEM）analysis.The carbon sequestration efficiency of CMWB was calculated through thermogravimetric analysis,and the CO₂ utilization efficiency of CMWB was obtained.The hydration products and carbonation products of CMWB were also studied in detail,and their chemical reaction mechanism was elucidated.（4）A design study was conducted on the engineering geological conditions of CMWB in the Hanglaiwan coal mine,analyzing the distribution characteristics of overlying rock stress and fissures under different CMWB filling ratios,and determining the coupling relationship between the height of water-bearing fissure zones and filling ratios.The research results will be applied in engineering practice at the Hanglaiwan coal mine,promoting water retention mining,CO₂ and coal-based solid waste resource utilization,and contributing to the construction of green and low-carbon mines.