基于PVM技术的充填膏体搅拌过程细观结构演化

Meso-structure evolution of cemented backfill paste during mixing process based on PVM technology

膏体性能是体系内部不同颗粒、组分之间协同作用的结果,探明充填料浆在搅拌作用下细观结构形态的演化过程,对完善膏体搅拌理论、改善膏体充填性能、实现矿山降本增效具有重要意义。采用激光颗粒显微成像(PVM)技术获取膏体料浆在不同搅拌时刻的细观结构图像,经二值化处理后应用Avizo软件得到料浆中团聚体的等效直径(d),来表征膏体细观结构特征,并基于Blake-Kozeny方程及Hattori-Izumi理论构建d-t关系模型,最后将所得实验值和理论值进行对比分析。研究结果表明:膏体搅拌制备过程分为浸湿黏结和剪切分散2个阶段,在搅拌作用下料浆细观结构的等效直径先增大后降低,最终趋于稳定。在浸湿黏结阶段,颗粒与液体之间形成类似“核-壳”结构,并在液桥力的作用下不断吸附周围的颗粒,随着被吸附的颗粒越来越多,“核-壳”结构尺寸渐渐增大(d与时间t的0.5次方成正比),并在35 s左右达到峰值;在剪切分散阶段,“核-壳”结构的体积分数达到临界状态无法吸附更多颗粒,团聚体在剪切力的作用下发生破裂,细观结构的等效直径不断变小(d与t成反比),并于300 s后趋于稳定,物料转变为均质“膏体”状态。基于等效直径的细观结构演化模型量化了充填料制备过程,促进了固废充填技术的完善。

Cemented paste backfill(CPB)performance is the result of the synergy between different particles and components in the system.It is of great significance to explore the evolution process of the meso-structure of the filling slurry under the action of mixing,which improves the backfill performance and achieves cost reduction in the mines.In this study,Particle Video Microscope(PVM)technology was used to obtain some meso-structure images of the CPB at different mixing times.Then the images were binarized,and the equivalent diameter(d)of aggregate in the slurry was obtained using Avizo software to characterize the meso-structure characteristics of the CPB.Based on the Blake-Kozeny equation and the Hattori-Izumi theory,a d-t relationship model was constructed,and finally,the obtained experimental and theoretical values were compared and analyzed.The results show that the preparation process of CPB is divided into two stages:granule nucleation and shearing dispersion.Under the action of mixing,the equivalent diameter of the aggregate in the slurry increases first and then decreases,and finally tends to be stable.In the granule nucleation stage,a similar“nuclear-shell”structure is formed between particles and liquids,and surrounding particles are continuously adsorbed under the action of liquid bridge force.As more and more particles are adsorbed,the size of the“nuclear-shell”structure gradually increases(The equivalent diameter is proportional to the 0.5 power of time)and reaches a peak around 35 s.In the shearing dispersion stage,the“nuclear-shell”structure cannot adsorb more particles due to its critical volume concentration.The agglomerates break under the action of shearing force,and the meso-structure size becomes smaller and smaller(The equivalent diameter is inversely proportional to time),and tends to be stable after 300 s.The material is transformed into a homogeneous paste state.The meso-structural evolution model based on the equivalent diameter quantifies the backfill material preparation process,and the research results promote the improvement of solid waste backfill technology.