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Background <p>Microbially induced calcium carbonate precipitation (MICP) has been increasingly applied for tailings reinforcement; however, its injectability, diffusion heterogeneity, and strength-porosity evolution under engineering-scale grouting conditions remain insufficiently understood. In particular, the reliability of pore-size-based injectability prediction and the mechanical consequences of spatially non-uniform cementation require systematic investigation.</p> Methods <p>A large-scale pressurized column model was established to simulate repeated bio-grouting in fine-grained metal tailings. Dye tracing was used to visualize diffusion patterns, while mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and triaxial shear tests were performed to characterize pore structure evolution and mechanical behavior. The strength–porosity relationship was analyzed using Mohr–Coulomb parameter inversion and nonlinear regression via artificial neural networks (ANN).</p> Results <p>Although 93.86% of pore volume is theoretically injectable based on pore-size analysis, dye tracing reveals preferential flow and stagnant zones, indicating that static injectability criteria overestimate effective diffusion. Transport is controlled by dynamic processes rather than pore size distributions alone. Spatially heterogeneous cementation produces non-uniform pore restructuring and localized crack networks partially filled with calcium carbonate. Mechanical testing indicated that both cohesion and internal friction angle increased with decreasing porosity, with a plateau in friction angle observed below 27%. An artificial neural network (ANN) was employed to describe the nonlinear evolution of strength with porosity, highlighting a change in the rate of mechanical parameter variation.</p> Conclusion <p>The results demonstrate that grout transport in fine-grained tailings is governed by dynamic hydro-bio-mechanical coupling rather than pore size alone. Effective reinforcement depends on the interaction between diffusion heterogeneity and cementation redistribution, leading to nonlinear mechanical evolution. These findings provide a more realistic basis for evaluating MICP performance in engineering-scale tailings treatment.</p>

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Experimental study on bio-grouting in metal tailings: injectability, diffusion heterogeneity and strength-porosity relationship

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月26日

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  • Yuxiang Pan,
  • Heinz Konietzky,
  • Zhijun Zhang,
  • Kang Tao,
  • Rong Gui

摘要

Background

Microbially induced calcium carbonate precipitation (MICP) has been increasingly applied for tailings reinforcement; however, its injectability, diffusion heterogeneity, and strength-porosity evolution under engineering-scale grouting conditions remain insufficiently understood. In particular, the reliability of pore-size-based injectability prediction and the mechanical consequences of spatially non-uniform cementation require systematic investigation.

Methods

A large-scale pressurized column model was established to simulate repeated bio-grouting in fine-grained metal tailings. Dye tracing was used to visualize diffusion patterns, while mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and triaxial shear tests were performed to characterize pore structure evolution and mechanical behavior. The strength–porosity relationship was analyzed using Mohr–Coulomb parameter inversion and nonlinear regression via artificial neural networks (ANN).

Results

Although 93.86% of pore volume is theoretically injectable based on pore-size analysis, dye tracing reveals preferential flow and stagnant zones, indicating that static injectability criteria overestimate effective diffusion. Transport is controlled by dynamic processes rather than pore size distributions alone. Spatially heterogeneous cementation produces non-uniform pore restructuring and localized crack networks partially filled with calcium carbonate. Mechanical testing indicated that both cohesion and internal friction angle increased with decreasing porosity, with a plateau in friction angle observed below 27%. An artificial neural network (ANN) was employed to describe the nonlinear evolution of strength with porosity, highlighting a change in the rate of mechanical parameter variation.

Conclusion

The results demonstrate that grout transport in fine-grained tailings is governed by dynamic hydro-bio-mechanical coupling rather than pore size alone. Effective reinforcement depends on the interaction between diffusion heterogeneity and cementation redistribution, leading to nonlinear mechanical evolution. These findings provide a more realistic basis for evaluating MICP performance in engineering-scale tailings treatment.