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

Particle distribution of debris flow sources usually plays an important role in the initiation of debris flows, and is an impor?tant parameter for design of debris flows’prevention. It is well known that the source’s feature of mine debris flows is different fromthat of common debris flows. In this paper, the controlling effect between particle distribution of mining waste and initiation of minedebris flows was studied on the basis of a series of indoor soil tests. The results show that the mining wastes are some loose solid mate?rials 0.075mm to 470mm 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 thanthe tailings, twice larger than the residual soil, and 4.9 times larger than the debris sources of Jiangjiagou debris flow. In fact, the realpermeability coefficient of mining waste residues is larger than the experimental data. Generally speaking, the mine waste debris flowsseldom result from the normal rainfall because of some features such as looseness, non-cohesion, high-porosity and high-permeabili?ty. In comparison with several debris flows that have occurred in the study area, the authors put forward a new initiation mode for mine waste debris flow. It is held that the reasonable prevention measures should include ①dredging the flood channels, and ②build?ing the dregs retaining walls and avoiding gravity dams.