密集导流孔和收液巷道耦合作用下离子型稀土原地浸矿渗流规律研究

In-site leaching ore is one of the green and efficient mining technology recycling rare earth resources. There are about 70% of rare earth mines having not intact baseboard in Gannan (in the south of Jiangxi Province), so the recycled liquid technique became the bottleneck in in-site leaching application and extension. The leaching hydrodynamic study on the leaching solution is analyzed rarely and intensively. The efficiency of recycled solution is low due to the arrangement of recycled solution engineering based on the experience. The infiltration process of in-site leaching mine of ionic rare earth and seepage law under the coupling action of dense diversion holes and recycled solution workings are studied. The pore structure and seepage resistance during the leaching mine process of rare earth are considered by the scanning electron microscopy (SEM) technology and hydrodynamic dispersive theory. Then the seepage model is established. The effect range of only one diversion hole and seepage field responding rule is investigated. At the same flow and the flow direction, the calculation model of the equivalent seepage parameter of rare earth mine under the dense diversion holes action is presented. Under the different pore structure and seepage principal axis of rare earth mines, the effect of seepage cracks of baseboard and diversion holes and recycled liquid workings on in-site leaching ore seepage field is discussed. The seepage fissure zone location and quantitative evaluation are studied based on the seepage principal axis and seepage field of rare earth ore change rule. Controlling method of lixivium flow direction and flow velocity is presented by the diversion holes and recycled workings. The study results will provide theoretic guidance for efficiently controlling seepage field and improving recycled liquid technique.

"原地浸矿"是绿色高效回收稀土资源的开采工艺，赣南稀土矿山中70%不具备完好底板，收液技术成为"原地浸出"工艺推广的瓶颈。目前对溶液的浸取水动力学缺乏深入研究，主要依靠经验布置收液工程，导致收液效率低，为此开展密集导流孔和收液巷道耦合作用下离子型稀土原地浸矿渗流过程和规律研究。项目采用扫描电镜技术和水动力弥散理论相结合分析稀土矿体浸矿过程中孔隙结构和渗流阻力的变化规律，建立相应的渗流模型；分析单一导流孔的影响范围和渗流场的响应规律，基于流量相等和流向相同的原则，建立密集导流孔作用下矿体等效渗流参数的计算模型；在不同稀土矿体孔隙结构和渗透主轴条件下，研究底板渗漏裂隙、导流孔和收液巷道对原地浸矿渗流场的影响规律，基于稀土矿体渗透主轴和渗流场变化规律进行渗漏裂隙带定位和量化评价，提出通过导流孔和收液巷道控制浸出液流向和流速的方法。研究成果为有效控制渗流场和发展收液技术提供理论指导。

目前有关原地浸矿工艺的渗流力学方面的理论和试验研究几乎空白，为此，项目主要开展了浸矿过程矿体土性参数变化，密集导流孔孔周水压力分布规律，建立单孔注液强度和影响范围的计算模型，原地浸矿渗流规律的理论和试验研究，提出原地浸矿注液和收液工程布置优化方法，主要结论如下：.(1)柱浸试验结果表明：浸矿过程中影响渗透系数变化的原因主要有离子吸附、离子交换和微颗粒迁移3个方面的原因，当水力梯度小于1.25时，离子吸附和离子交换对渗透系数有明显影响；当水力梯度为2时，微颗粒迁移与离子吸附和离子交换对渗透系数的影响相当；水力梯度为3时，微颗粒迁移对渗透系数影响起主导作用，为研究注液孔入渗堵塞积累了数据。.(2)密集导流孔研究结果表明：导流孔布置方式对母液回收率影响非常大，当导流孔平均间距为50cm和初始压力水头为47cm条件下，均匀布置导流孔时溶液回收率达到73.7%；非均匀布置时溶液回收率降低至43.3%；合理确定导流孔间距可以大幅度降低原地浸矿渗流场的初始压力水头，导流孔平均间距由0.5m减小至0.25m，溶液回收率由73.7%增加至79.3%，初始压力水头由47cm减小至20cm，减幅为57.4%，为合理确定导流孔间距提供了依据。.(3)试验矿块现场监测结果表明：试验矿块在注液强度为740m3/d时，在注液第42天渗流达到稳定，矿层的饱和体积比只有63%，有高达37%的矿体难以被硫酸铵溶液浸泡。在渗流稳定调节期，注液强度由740 m3/d增加到860 m3/d，矿层的饱和体积比也增加到71.3%，但在渗流稳定期浸矿液已从硫酸铵溶液换成上清液，氨根离子的浓度已大大降低，稀土离子交换效率降低，资源回收率不完全，这是造成龙南稀土矿区“复灌”现象普遍存在的重要原因，解释了赣南“复灌”现象。.(4)注液孔入渗的理论试验研究，结果表明：注液孔的间距增加，资源浸取率降低，龙南类型稀土矿体的孔间距应控制在1.5m~2.0m范围内，为确定龙南类型稀土矿山注液孔间距提供依据。.(5)导流孔和収液巷道对边坡稳定性影响的研究结果表明：当导流孔收液率小于13.35%时，导流収液对边坡安全系数影响很小；当导流孔收液率为13.35%~15.8%时，边坡安全系数随收液率近似成线性增加。对于长度为40m的边坡，収液巷道与出渗面距离为12m~24m时，巷道对控制边坡失稳的作用发挥得最充分，为同类稀土矿山提供参考。