Abstract:

Microbially induced carbonate precipitation (MICP) shows strong potential for reinforcing uranium tailings dams because it is environmentally friendly and efficient. However, spatial heterogeneity in the treated mass limits engineering applicability. To quantify strength heterogeneity in MICP-treated uranium tailings sand, we first used response surface methodology to evaluate how grouting parameters affect strength and its dispersion. Next, we determined the probability distribution of strength by fitting macroscopic strength data obtained under individual grouting conditions. Finally, we analyzed strength evolution and failure mechanisms using calcium carbonate content and spatial distribution, scanning electron microscopy-energy dispersive spectroscopy (SEM–EDS) observations, and macroscopic fracture characteristics. We propose a random discrete element model based on a Beta distribution and define a cementation state index to quantify the macroscopic reinforcement effect inferred from the fitted strength distribution. The results show that reinforcement is maximized at a cementation-solution concentration of 1 mol/L and pH 7. Higher solution concentrations (≥0.9 mol/L) and lower pH (≤7) significantly enhance reinforcement. The strength distribution is right- skewed. The Weibull (AD =0.773) and log-normal (AD =0.32) distributions fit the data better than the normal distribution (AD = 3.616). Failure occurs as progressive brittle fracture, and the Beta-distribution-based random discrete element model captures the resulting heterogeneous mechanical behavior. These findings provide a theoretical basis for optimizing MICP parameters and guiding engineering applications.

Key words: microbially induced carbonate precipitation (MICP), uranium tailings sand, heterogeneity, progressive failure, discrete element method (DEM)