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This study involves an experimental examination of compression behaviors of fly ash stabilized marine clay cured at different times concerning the influences of pore water salinity. A set of laboratory one-dimensional compression tests was conducted on soft Lianyungang marine clay specimens with various pore water salinities and stabilized with fly ash. Test results indicated that both salinity and curing time influenced the compression characteristic of fly ash stabilized clay. The presence of fly ash obviously reduced the compressibility of the untreated marine clay sample. The semi-logarithmic compression curve of untreated pure soil was a straight line, whereas fly ash stabilized clay samples exhibited the pattern of two straight lines. All the fly ash stabilized soil specimens were well represented by two straight lines in the bilogarithmic coordinate, making it convenient to determine the compression yield stress. The compression index at the pre-yield stage was not susceptible to the variation in the salinity and curing period, whereas at the post-yield stage it exhibited a downward tendency as salinity and curing time increased. The value of yield stress for stabilized marine clay specimen exhibited a downward tendency with increasing salinity, whereas it increased significantly within 7 days and tended to level off with the elapsed curing time. The adverse effect of salinity and the positive influence of curing time on yield stress should be considered in engineering applications. [ABSTRACT FROM AUTHOR]

CO2 + O2in-situ leaching (ISL) of sandstone-type uranium ore represents the third generation of solution mining in China. In this study, reactive transport modeling of the interaction between hydrodynamic and geochemical reactions is performed to enable better prediction and regulation of the CO2 + O2in-situ leaching process of uranium. Geochemical reactions between mining solutions and rock, and the kinetic uranium dissolution controlled by O2 (aq) and bicarbonate ( HCO 3 - ) are considered in the CO2 + O2 ISL reactive transport model of a typical sandstone-hosted uranium ore deposit in northern China. The reactive leaching of uranium is most sensitive to the spatial distribution of the mineralogical properties of the uranium deposit. Stochastic geostatistical models are used to represent the uncertainty on the spatial distribution of mineral grades. A Monte Carlo analysis was also performed to simulate the uranium production variability over an entire set of geostatistical realizations. The ISL stochastic simulation performed with the selected geostatistical realizations approximates the uranium production variability well. The simulation results of the ISL reactive transport model show that the extent of the uranium plume is highly dependent on mineralogical heterogeneity. The uncertainty analysis suggests the effect of uranium grade heterogeneity was found to be important to improve the accurate capture of the uncertainty. This study provides guidance for the accurate simulation and dynamic regulation of the CO2 + O2 leaching process of uranium at the scale of large mining areas. [ABSTRACT FROM AUTHOR]