铁矿干排尾矿坡面生态恢复侵蚀调控机理研究

Dry tailings, which is an emerging technology, eliminates the potential safety hazard of water leakage and dam-break of wet process, but the water erosion, desertification, extreme infertility and difficult to inhabit for vegetation in slope of dry tailings, is still a urgent problem to be solved. So based on the six kinds of ecological restoration models centring around runoff regulation, substrate amelioration, vegetation inhabitation, by means of field runoff plots and indoor simulation analysis, the slope of dry iron tailings located in the Xiaolangdi reservoir upstream YuanQu, Shanxi, was selected to study the slope surface erosion process, reinforcement of root-soil composite and vertical erosion. The transport characteristics of slope runoff and sediment in the direction of slope and vertical and affecting factors of six kinds of ecological restoration were studied to reveal erosion regulation mechanism of ecological restoration in dry tailings slope and optimize ecological restoration model. The scientific value of results is to provide theoretical platform for rapid ecological restoration of extreme degraded ecosystem in dry tailings slope. Applications value is to provide ecological restoration demonstration effect for local mining area in a small scale, and to provide theoretical basis for ecological restoration and sustainable development of other similar extreme habitat mining area in wider range.

尾矿干排技术是一种新兴的技术，虽然消除了湿排的水分渗漏、溃坝等安全隐患，但是尾矿干排陡坡面的水蚀沙化、极端贫瘠、植被定居困难仍然是一个亟待解决的问题。因此本研究以小浪底库区上游山西垣曲段土石山区铁矿尾矿干排坡面为研究对象，基于前期以径流调控、基质改良、植被定居为核心建立的六种生态恢复模式，通过野外径流小区与室内模拟分析，主要研究六种生态修复模式坡面侵蚀过程，六种生态修复模式根土复合体的固土特性，六种生态修复模式的垂直侵蚀特征。分析六种生态修复模式坡面径流的坡向和垂直向的泥沙运移特征及影响因素，揭示干排尾矿坡面生态修复的侵蚀调控机理，优化生态修复模式。研究结果科学价值在于：为进一步揭示干排坡面极度退化生态系统的快速生态恢复机理提供理论平台；应用价值：小范围对于当地矿区废弃地生态恢复提供示范作用，大范围对于其它类似极端生境下的生态恢复及矿区的可持续发展提供理论依据。

中国铁矿石储量位居世界第四，平均品位仅为 34.29%，较全球平均品位低 10.45%，采掘量大，排弃量多，堆存的铁尾矿量占全部尾矿堆存总量的近1/3。干排尾矿基于干料和水的最大化分离，消除了传统湿排的水分渗漏、溃坝、环境污染、占地面积大等问题，但也面临着沙化、水土流失、植被定居困难等生态修复问题。本研究基于山西省垣曲县的干排铁尾矿生态恢复基地，利用室内模拟和原位观测两种手段，围绕水分垂直运移和坡面水平运移，对不同复垦模式下的水沙运移进行研究。结果表明：van Genuchten模型能够很好地拟合尾矿砂的水分特征曲线，Kostiakov 模型能很多好地解释尾矿砂的入渗过程。坡度、雨强、基质类型和植被对坡面侵蚀特征密切相关。干排尾矿砂自然紧实度高，入渗率低，缺乏有机结构体，易产沙高流速高径流，径流剪切力增大，产沙率高，侵蚀细沟易向深向长发展，平面形态上属于“瘦长薯条型”。添加菌糠的尾矿砂由于结构性结皮增加表层的粗糙度和阻力系数，有效分散径流，消减径流剪切力，抑制侵蚀沟的三向发展，使得产沙量减少，但产流量增大。添加土壤的尾矿砂入渗性增强，但在35°陡坡下沟壁坍塌细沟易向两侧扩展，细沟平面形态上属于“花瓶型”。与未复垦尾矿相比，植被减沙效果显著，但是减流效果不显著，整体来看，尾矿砂中混入土和菌糠（TSM），树种为刺槐*连翘，油松*紫穗槐，阶状整地的修复模式最好，能有效地拦截坡面径流泥沙。研究结果丰富了无土矿区的土壤替代研究，为尾矿的生态恢复和土壤侵蚀控制提供了重要的理论基础。