尾砂絮团结构剪切演化特征及对深锥浓密性能影响机制

The increase of tailing slurry concentration is essential for improving the filling effectiveness, and the shear time-varying characteristics of flocs structure and strength of tailings are intrinsic factors for the increase of tailing slurry concentration. This project, based on bed heterogeneity assumption which is different from traditional homogenizing assumption, further studied the shear evolution of flocs structure and the thickening mechanism. Firstly, the micro-structure images of individual and group flocs should be taken to calculate the sizes and fractal dimensions of flocs, and to analyze the evolution characteristics of flocs structure before and after shearing as well as its influence on thickening effects. Secondly, the process of stress, damage and reverse seepage of flocs at different time was identified according to the changing tendency of shear rheological parameters of flocs. And the pattern of how the group flocs were damaged and consolidated was proposed. Thirdly, the continuous slurry discharge and shearing action were brought in for perfecting the theory of deep cone thickening performance prediction under dynamic conditions. Meanwhile, a new model for solid flux calculation was proposed. At last, how the underflow density was influenced by these factors was analyzed and the influence factors and their weight of deep cone thickening performance were clarified by changing the shearing structure parameters. And the control mechanism was proposed to optimize the shear rate. This study, contributing to the development of deep cone thickener theory and the paste filling technology of China, clarified the evolution mechanism of flocculation micro-structure under shearing, revealed the enrichment and discharge mechanism of internal moisture of group flocs and developed the prototype of strengthening thickening technique of tailings.

提高尾砂浆浓度是改善充填效果的必由之路，尾砂絮团结构及强度的剪切时变特性是影响尾砂浓度提高的内在原因。区别于传统均质假设，本项目在床层非均质假设的基础上深入开展尾矿絮团结构剪切演化特征与浓密机理研究：首先，获取单体、群体絮团细观结构图像，计算絮团尺寸与结构分形维数，分析剪切前后絮团结构演化特征及对浓密效果的影响机制；然后，分析絮团群剪切流变参数变化趋势，识别絮团在不同时段的受力-破坏-逆向渗流过程，提出絮团群破坏与密实模式；再次，引入连续排料和连续剪切作用，完善动态条件下的深锥浓密性能预测理论，提出固体通量计算新模型；最后，改变剪切结构参数，分析各因素对底流浓度的影响规律，探明深锥浓密性能的影响机制及权重，提出剪切速率优化调控措施。本研究将阐述剪切条件下絮团细观结构演化机制，揭示絮团群内部水份的富集排出机理，形成尾矿强化浓密技术原型，发展深锥浓密理论，为我国膏体充填技术的发展提供理论支撑。

本项目以提高尾砂浆浓度、改善超细尾砂浓密效果为目的，综合运用室内试验、理论分析及计算机模拟等方法，对深锥浓密过程中尾砂絮团结构的演变规律以及底流浓密稠化机制展开研究，取得了以下研究成果：. （1）研究手段：本项目利用小型室内连续浓密试验平台开展动态浓密实验，该平台克服静态量筒沉降实验的局限性，模拟现场真实作业工况，提高了研究结果的可靠性。. （2）研究内容一：剪切条件下的絮团结构特征及演化。分析了絮凝沉降过程中的絮团速度场，探究絮团演化分形维数变化规律，得到絮团沉降速度与絮团尺寸之间的响应关系，揭示了剪切作用对沉降速度的影响机制。. （3）研究内容二：絮团可浓密性能表征。分析絮团自由沉降和床层压缩渗透力学行为，基于絮团碰撞生长动力学探明剪切作用影响下的絮团强度变化规律。研究了沉降和压缩过程中的力学相似性，提出了包含干涉沉降函数与压缩屈服应力双参数的全尾砂絮团全浓度范围可浓密性能表征方法。. （4）研究内容三：絮团强度形成和破坏密实机理。基于三维重构技术与PNM理论提取分析微米级别的压缩絮团结构和导水通道形貌，分析了搅拌前后絮团结构的演化及封闭水分的分布特征，探明了剪切作用对导水通道的影响机制，揭示了压缩床层内部絮团破坏密实和封闭水分排出的动力来源与作用机理。. （5）研究内容三拓展：床层底部絮团结构可视化表征和形态分析。发现剪切作用对絮团浓密处置有促进作用，并且底层絮团结构较上层絮团结构更致密。对絮团孔隙结构进行了类型划分和孔隙结构特征参数分析，研究了絮团在剪切作用下浓密脱水特性，探究了逆向渗流的形成机制。. （6）研究内容四：基于可浓密性能的固体通量预测。利用MATLAB编程软件进行编程迭代，分析了尾砂浓密力学平衡方程，对深锥设备的浓密性能进行模型预测。. （7）研究内容五：动态剪切条件下深锥浓密过程模拟。分析了浓密机中絮团浓度分布云图，研究了湍流动能的强度分布。通过建立群体平衡模型预测了絮团粒径分布，分析了剪切条件下全尾砂浆体的浓密性能。