采矿废渣颗粒粒径对矿渣型泥石流起动的控制作用——以小秦岭金矿区为例

Controlling role of particle sizes of mining waste residues in the initiation of mine debris flow:A case study of the Xiaoqinling gold mining area

泥石流物源的颗粒级配大小对于泥石流的起动具有重要的控制作用,亦是泥石流防治工程设计的重要参数。采矿废石渣构成的矿渣型泥石流,物源特性不同于一般的泥石流。通过对小秦岭金矿区采矿废石渣、尾矿沙、残坡积土的颗粒级配、孔隙度、透水性能的研究,与其他地区泥石流物源级配进行了差异对比,探讨了采矿废渣颗粒级配对泥石流起动的制约影响。研究表明,采矿废石渣松散无联结,粒径变化于0.075~470mm之间,其中大于2mm的砾级含量占总渣量的93.33%,平均粒径为61.2mm,以卵石级为主,粘粒物质几乎没有。粒径小于5mm的废石渣的渗透系数是选矿尾矿渣的103.5陪、残坡积土的2倍、蒋家沟泥石流物源的4.9倍,实际上采矿废石渣堆的渗透系数比试验测试的数据更大。废石渣的松散无联接、高孔隙率及极高渗透性的特点,决定了常遇降水难以导致废石渣堆起动。结合研究区历史上发生的泥石流,构建了堵溃型矿渣型泥石流起动模式,据此提出了清理占据行洪通道的废渣、疏浚行洪通道、修建拦渣挡墙的泥石流防治理念,避免拦沟修筑重力坝。

Particle distribution of debris flow sources usually plays an important role in the initiation of debris flows, and is an important parameter for design of debris flows’ prevention. It is well known that the source’s feature of mine debris flows is different from that of common debris flows. In this paper, the controlling effect between particle distribution of mining waste and initiation of mine debris flows was studied on the basis of a series of indoor soil tests. The results show that the mining wastes are some loose solid materials 0.075 mm to 470 mm in particle diameter（lots of pebbles and minor clays）, with mean grain size of 61.2mm. Furthermore, the seepage tests indicate that the permeability coefficient of mining waste residues（particles smaller than 5mm） is 103.5 times larger than the tailings, twice larger than the residual soil, and 4.9 times larger than the debris sources of Jiangjiagou debris flow. In fact, the real permeability coefficient of mining waste residues is larger than the experimental data. Generally speaking, the mine waste debris flows seldom result from the normal rainfall because of some features such as looseness, non-cohesion, high-porosity and high-permeability. In comparison with several debris flows that have occurred in the study area, the authors put forward a new initiation mode formine waste debris flow. It is held that the reasonable prevention measures should include 1dredging the flood channels, and 2building the dregs retaining walls and avoiding gravity dams.