The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied ...The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied using an X-ray fluorescence analyzer, scanning electron microscope, and electron probe. Results revealed that the composition, structure, and mineral phase of the original layer, transition layer, and affected layer of the metering nozzle differed because of stabilizer precipitation and steel slag permeation. The stabilizer MgO formed low-melting phases with steel slag and impure SiO2 on the boundaries（pores） of zirconia grains; consequently, grain fracturing occurred and accelerated damage to the metering nozzle was observed.展开更多
Assessment of mining impact on groundwater is one of critical considerations for longwall extension and sustainability,however usually constrained by limited data availability,hydrogeological variation,and the complex...Assessment of mining impact on groundwater is one of critical considerations for longwall extension and sustainability,however usually constrained by limited data availability,hydrogeological variation,and the complex coupled hydro-mechanical behaviour.This paper aims to determine the factors and mechanism of groundwater depressurisation and identify knowledge gaps and methodological limitations for improving groundwater impact assessment.Analysis of dewatering cases in Australian,Chinese,and US coalfields demonstrates that piezometric drawdown can further lead to surface hydrology degradation,while the hydraulic responses vary with longwall parameters and geological conditions.Statistical interpretation of 422 height of fracturing datasets indicates that the groundwater impact positively correlates to panel geometry and depth of cover,and more pronounced in panel interaction and top coal caving cases.In situ stress,rock competency,clay mineral infillings,fault,valley topography,and surface-subsurface water interaction are geological and hydrogeological factors influencing groundwater hydraulics and long-term recovery.The dewatering mechanism involves permeability enhancement and extensive flow through fracture networks,where interconnected fractures provide steep hydraulic gradients and smooth flow pathways draining the overlying water to goaf of lower heads.Future research should improve fracture network identification and interconnectivity quantification,accompanied by description of fuid flow dynamics in the high fracture frequency and large fracture aperture context.The paper recommends a research framework to address the knowledge gaps with continuous data collection and field-scale numerical modelling as key technical support.The paper consolidates the understanding of longwall mining impacting mine hydrology and provides viewpoints that facilitate an improved assessment ofgroundwaterdepressurisation.展开更多
基金funded by the National Natural Science Foundation of China(51372193)the Natural Science Basic Research Plan in the Shaanxi Province of China(2014JM6224)
文摘The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied using an X-ray fluorescence analyzer, scanning electron microscope, and electron probe. Results revealed that the composition, structure, and mineral phase of the original layer, transition layer, and affected layer of the metering nozzle differed because of stabilizer precipitation and steel slag permeation. The stabilizer MgO formed low-melting phases with steel slag and impure SiO2 on the boundaries（pores） of zirconia grains; consequently, grain fracturing occurred and accelerated damage to the metering nozzle was observed.
文摘Assessment of mining impact on groundwater is one of critical considerations for longwall extension and sustainability,however usually constrained by limited data availability,hydrogeological variation,and the complex coupled hydro-mechanical behaviour.This paper aims to determine the factors and mechanism of groundwater depressurisation and identify knowledge gaps and methodological limitations for improving groundwater impact assessment.Analysis of dewatering cases in Australian,Chinese,and US coalfields demonstrates that piezometric drawdown can further lead to surface hydrology degradation,while the hydraulic responses vary with longwall parameters and geological conditions.Statistical interpretation of 422 height of fracturing datasets indicates that the groundwater impact positively correlates to panel geometry and depth of cover,and more pronounced in panel interaction and top coal caving cases.In situ stress,rock competency,clay mineral infillings,fault,valley topography,and surface-subsurface water interaction are geological and hydrogeological factors influencing groundwater hydraulics and long-term recovery.The dewatering mechanism involves permeability enhancement and extensive flow through fracture networks,where interconnected fractures provide steep hydraulic gradients and smooth flow pathways draining the overlying water to goaf of lower heads.Future research should improve fracture network identification and interconnectivity quantification,accompanied by description of fuid flow dynamics in the high fracture frequency and large fracture aperture context.The paper recommends a research framework to address the knowledge gaps with continuous data collection and field-scale numerical modelling as key technical support.The paper consolidates the understanding of longwall mining impacting mine hydrology and provides viewpoints that facilitate an improved assessment ofgroundwaterdepressurisation.
