剪切浓密床层孔隙网络模型与导水通道演化 |
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引用本文: | 焦华喆,王树飞,吴爱祥,沈慧明,杨亦轩,阮竹恩. 剪切浓密床层孔隙网络模型与导水通道演化[J]. 工程科学学报, 2019, 41(8): 987-996. DOI: 10.13374/j.issn2095-9389.2019.08.004 |
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作者姓名: | 焦华喆 王树飞 吴爱祥 沈慧明 杨亦轩 阮竹恩 |
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作者单位: | 1.河南理工大学土木工程学院, 焦作 454000 |
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基金项目: | 国家自然科学基金资助项目51704094国家自然科学基金资助项目51834001国家自然科学基金资助项目51574013河南省高等学校重点科研项目16A440003国家安全生产重大事故防治关键技术项目henan-0005-2016AQ |
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摘 要: | 剪切作用是膏体重力浓密制备的基础要素, 本文研究了浓密床层孔隙和喉道的变化对导水通道的影响, 揭示了水分排出的来源与比例. 开展半工业实验并结合计算机断层扫描(CT)与孔隙网络模型(PNM)提取床层微观孔隙结构, 利用最大球搜索算法识别并分析剪切前后孔隙与喉道的演化规律. 结果表明, 添加转速为2 r·min-1的剪切作用将尾砂底流浓度(即底流的固相质量分数)由55.8%提升到58.5%, 孔隙率由43.05%降低到36.59%, 孔隙率降低的比率为15%. 通过PNM技术将孔隙空间划分为"球体"储水孔隙与"棍体"喉道; 剪切后球体和棍体数量分别增加了16.5%和22%, 球体平均尺寸小幅下降, 球体半径多集中在40~60 μm之间. 棍体平均半径由9.83 μm降低至8.58 μm, 降低了12.7%, 棍体长度变化较小. 剪切作用下的球体配位数在5~10的部分从25.73%增加至44.58%, 配位明显增多, 颗粒接触紧密. 本文提出"球棍比"的概念用于孔隙结构的定量表征. 剪切后球体体积占比由14.14%降低至12.75%, 球体体积减少的比率达到9.83%;棍的体积由28.91%降低至23.84%, 棍体积减少的比率为17.54%. 球棍比由48.91%增加至53.48%, 球棍比提升的比率达到了9.34%, 与球体体积减小相比, 棍的体积减少的幅度更大, 导致球棍比上升. 本文从孔隙结构变化的角度揭示了全尾砂重力浓密剪切排水机理; 剪排水过程中主要排出的是喉道中的水分, 孔隙中的水分排出较少.
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关 键 词: | 膏体充填 重力浓密 剪切作用 孔隙率 导水通道 球棍比 |
收稿时间: | 2018-10-03 |
Pore network model of tailings thickener bed and water drainage channel evolution under the shearing effect |
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Affiliation: | 1.School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454000, China2.School of Civil and Resources Engineering, University of Science and Technology Beijing, Beijing 100083, China3.School of Resources and Environment, Henan Polytechnic University, Jiaozuo 454000, China |
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Abstract: | Shearing is the basic factor involved in gravity thickening of paste. This work focuses on the influence of pores and throats characteristics on water drainage channel evolution, and determines the proportion of discharged water in tailings thickener bed. Pilot-scale experiment combined with computed tomography (CT) and pore network model (PNM) technology to determine the micropore structure. The maximum ball algorithm is used to analyze the evolution of pores and throats with and without shearing. The results show that the tailings underflow concentration increases from 55.8% to 58.5% under 2 r·min-1 rake shearing and the porosity decreases from 43.05% to 36.59%, the decrease rate of porosity is 15%. The pore structure can be divided into two types, i.e., "balls" and "sticks, " by the PNM technology. The quantity of "balls" and "sticks" increases by 16.5% and 22%, respectively. However, the average radius of balls decreases slightly in the range of 40-60 μm under shearing. The average radius of sticks decreases from 9.83 μm to 8.58 μm, i.e., by 12.7%. Nevertheless, the length of sticks exhibits only a slight change. The coordination number of balls increases significantly from 25.73% to 44.58% in the range of 5-10 under shearing, and the particles are in close contact. The concept of "the volume ratio of pores to balls" is proposed for the quantitative characterization of the pore structure. The volume fraction of balls decreases from 14.14% to 12.75%, the decrease rate of volume fraction is 9.83%, and volume fraction of sticks decreases from 28.91% to 23.84%, the decrease rate of volume fraction is 17.54%. The volume ratio of balls to sticks increases from 48.91% to 53.48%, and increase rate of it is 9.34%. When the volume decrease of balls is more than that of sticks, the volume ratio of balls to sticks increases. This work reveals the shearing drainage mechanism of unclassified tailings gravity thickening from the perspective of pore structure change, i.e., the drainage is mainly discharged from the throat more than the pore from the tailings thickener bed shear dewatering process. |
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