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FIELD AND LABORATORY CHARACTERIZATIONS OF IN SITU COAL SLURRY
Restricted (Penn State Only)
Master of Science
Date of Defense:
June 22, 2018
Ming Xiao, Thesis Advisor
Shimin Liu, Thesis Advisor
Patrick Joseph Fox, Committee Member
Peak Particle Velocity
Over 200 coal tailings impoundments are classified as having high hazard potential by the Federal Emergency Management Agency’s hazard rating system. The coal tailings impoundment failures can be immensely destructive. The catastrophic tailings impoundment failures that happened in the United States such as the Buffalo Creek disaster in 1972, the Big Branch impoundment failure in 2000, and the Kingston Fossil Plant’s slurry spill in 2008, have resulted in huge social, economic, and environmental losses. Despite the scale of the failures, there are not enough data that are readily available for the stability analysis of the impoundments. Due to the scarcity of the current database, there is a need to conduct a comprehensive testing program to determine the necessary geotechnical parameters in order to realistically assess the stability of coal tailings impoundments upon various field impacts. The testing programs in this study included the field testing such as the standard penetration test (SPT), the conventional laboratory testing, the seismic survey using the field non-destructive testing such as seismic refraction survey and multichannel analysis of surface waves (MASW) method, and the seismic monitoring using seismographs to determine the particle velocity of coal tailings upon dynamic loadings. The basic index properties, consolidation properties, hydraulic conductivity, shear strength, shear modulus, and damping ratio of coal tailings were determined from the laboratory testing program and can be used as input parameters to any numerical models. The liquefaction susceptibility of coal tailings was also evaluated based on the laboratory testing results. Shear wave and primary wave velocities of coal tailings were determined based on the seismic survey field data. The elastic moduli that are critical in understanding the stress-strain relationship of coal tailings were estimated. The in situ dynamic properties of coal tailings deposited in both active and inactive impoundments were compared. The liquefaction potential of coal tailings upon the blast loadings was assessed based on data derived from the seismic survey and the seismic monitoring programs. All results from several testing programs indicated that the coal tailings may potentially liquefy upon strong ground motions. Other than the geotechnical properties, the mineralogical properties of the coal tailings were also characterized to evaluate the potential of coal tailings to be reutilized for fuel generation and extraction. The reutilization of coal tailings can potentially reduce, if not eliminate, the hazards posed by the coal tailings impoundments. In most studies, coal tailings were treated as having the same properties regardless of their origins (i.e. the coal ranks and basins from which the tailings are derived). Recognizing the differences in the properties of tailings resulting from the productions of coals with different ranks would help effectively select tailings that suit the requirements of various reprocessing and combustion technologies. In this study, the physical and mineralogical properties of two types of tailings produced from anthracite and bituminous coals were studied and compared. The following characteristics that have direct applications to the future coal tailings reprocessing and combustion were determined: absolute density, particle size, and elemental and mineral compositions. Based on the mineralogical properties, analyses show that coal fines are easier to be extracted or separated from anthracite tailings. The average particle size of both coal tailings, however, may need to be modified accordingly to meet the specifications of available combustion techniques.
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