Meitan xuebao (Apr 2024)
Mechanism of bubble action in backfill slurry and the evolution of its rheological properties
Abstract
Cemented paste backfill is a suspension composed of solid-liquid-gas three-phase. For a long time, the focus has been mostly on the rheological behavior of solid-liquid two-phase, while the effect of gas phase on slurry with complex rheological behavior remains obscure. The gaseous phase components can significantly reduce the yield stress and viscosity of high-concentration backfilling slurry, which plays a significant role on improving pipeline transportation performance and reducing pipeline wear. In order to reveal the mechanism of bubbles to its rheological properties of slurry, the gas content of slurry was controlled by adjusting the content of air entrainment agent (TTAB), and tests such as surface tension, air content and rheological properties were carried out to find out the influence of bubbles on the rheological behavior of slurry, and capillary force (Fcay) and the bubble evolution model of dimensionless yield stress (\begin{document}$ {\tau }_{{\mathrm{ref}}}/{\tau }_{{\mathrm{y}}} $\end{document}) were introduced to analyze the bubble evolution characteristics in the slurry and reveal the mechanism of bubbles on the rheological properties of slurry. The results showed that under the low gas content ( < 12.5%), the gas phase had little effect on the rheological behavior of the suspended slurry. As the increase of gas content, the effect of bubbles on the rheological behavior of backfilling slurry was immense. Under the action of the air-entraining, the bubble surface had a repulsive force on the fine particles in the slurry, and could reduce the adsorption capacity of cement and solid waste, resulting in a decreasing trend of slurry yield stress and increasing fluidity. Based on capillary force (Fcay) and dimensionless yield stress theory (\begin{document}$ {\tau }_{{\mathrm{ref}}}/{\tau }_{{\mathrm{y}}} $\end{document}), evolutional mechanism of rheological properties of slurry in different gas content was analyzed. It could be seen that as the gas content increased (12.5%−27.7%), the surface tension and yield stress of slurry decreased, and the bubble would be deformed by extrusion. When the gas content (28.6%) was high, the bubbles in the slurry were easy to burst. In addition, bubbles, retained inside the backfilling body, leading to strength degradation, so the effect of bubbles on the mechanical properties of the backfilling body and its solution were explored and three effective measures were proposed. By revealing the effect of bubbles on the rheological properties of suspension slurry and its evolution characteristics, it provides theoretical support for the development of high bubble filling, which can achieve the goal of drag reduction and friction reduction.
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