Seepage Analysis Of Gejiu Xiangchong Tailing Pond

Tailing Pond, which is used for storing mine tailings, is an artificial structures with high potential-energy, is the major source of pollution for each metal and nonmetal mines. If tailings drainage installations poorly designed or damage to the facility, it will cause saturation line library is too high, resulting in accumulation of tailings dam seepage slope, soil flow and piping, and then lead to dam accident. Once the dam break accident occurred, bank deposits nearly saturated tailings would rush out to the downstream people’s lives and property safety threat. Also, because the majority of tailings beneficiation reagent containing toxic substances such as dam will cause tremendous pollution on the ecological environment of the area near the reservoir area.In this study, with a large number of field investigation, this paper described the engineering geological background of Gejiu Xiangchong Tailing Pond area in detail, and carried out a series of surface hydrogeological evaluation. On the basis of topographic maps, field survey drilling, field test and laboratory test data, by using the professional seepage simulation software ---- Geo-SEEP/W (2D) and Visual MODFLOW (3D), this paper also do a chain of numerical simulations of seepage field, and obtained some seepage field features of this Tailing Pond. Main conclusions are follow:(1) The structure nearby the project area are mainly three groups ---- EW, NE, SN. Among them, the EW structure is formed first time, the performance of a series of pairs of parallel EW trending folds and faults consisting of compression-shear extrusion zone. Most segmented fault folds north south steep slow, even reverse the south. South of the project area, the development of a series of NE-trending fault, which extends more in length between 3-5 km, in the north-east the Red River fault echelon disc was distributed, and the Red River fault zone (and its secondary faults) an angle greater than 45°, in particular its effect on the formation of dislocation significantly, should belong to the supporting structure of the Red River shear fault motion late Himalayan dextral shear slip formation. The main north-south trending structures in old fracture, fracture Jiajieshan represented by its geomorphological features significantly, breaking the overall strike 350°～353°, the tendency west, dip 44°～56°.(2) Precipitation is the main source of groundwater in the project area, as loose deposits (residual sediments and Slumping, etc.) in the pore water as its main way of occurrence, and Koizumi were planar seeping groundwater excretion way, gullies are the main excretion channels. Slate bedrock of integrity and good impermeability to prevent the reservoir water infiltration, providing favorable conditions for the construction of Tailing Pond.700 m elevation above the northern slopes of the groundwater is the main area exposed, the final surface elevation above the Tailing Pond, Tailing Pond drainage is to provide a great convenience.(3) Under the two-dimensional steady seepage field Tailing Pond, tailings library flow smoothly overall, the overall flow of the fill dam to dam the early direction, did not show the direction of flow "Change", "reversal" phenomenon; the layers of the layer by the flow rate permeability coefficient, in which it Quaternary unconsolidated sediments layer (Q) in the maximum flow velocity; the greater the length of the dry beach, fill dam crest greater the depth of infiltration of the bottom line, that is by affecting the accumulation of dry beach below the dam crest infiltration the depth of the line to adjust the overall depth of the saturation line, while the initial impact of the dam near the saturation line depth is not significant; the greater the ratio of initial dam and fill dam permeability coefficient (Ki/Kd) is (the better of the initial dam penetration), the bigger the horizontal distance of infiltration curve and intersection of foundation and initial distance between the dam upstream toe is, the greater the depth of infiltration of the curve is, that is the initial dam upstream toe near the saturation line penetration depth of the initial dam respond more strongly, but higher than the initial fill dam permeability coefficient permeability coefficient when more than three orders of magnitude, depth of invasion line stabilized.(4) Under conditions of steady seepage field, three-dimensional and two-dimensional results are agreement, but the results are generally larger than the two-dimensional three-dimensional results. Theoretically, three-dimensional model is closer to the actual situation of the project, so the actual project construction should take three-dimensional results as a reference.(5) In the three-dimensional steady seepage field, the seepage face of Gejiu Xiangchong Tailing Pond is not always a level surface. In the rear of the dry beach, the seepage face and Tailing Pond surface are level, bank head with different topography and changes in the permeability of the formation change, in line with the direction of the water flow "law of refraction"; the downstream direction from the dry beach, seepage surface is a slope as "the left bank of tall, the right bank of low" slope, reservoir water infiltration and migration in addition to the initial direction of the dam, but also accompanied by the right bank to the left bank of Tailing Pond component, showing a three-dimensional flow characteristics.(6) Under the climatic conditions of the project area, with the increase of rainfall intensity, saturation line of tailings pong continued to climb. At the end of dry season and the beginning of rainy season, saturation line is close, just a few meters, to the downstream slope of fill dam. At the end of rainy season, it has coincided with the downstream slope, leading a large area of water seepage; rainfall intensity did not have a greater impact on the depth of the initial dam near the saturation line, the seepage face always crosses the initial dam from the middle, tailings pond has a great threat to the safe operation.(7) Through the study of various boundary conditions MODFLOW software package, this paper tried the stress subroutine MODFLOW packages drain (DRAIN) to simulate the neumann boundary conditions, and applied to determine the three-dimensional surface Tailing Pond infiltration problem, the convergence was in good condition, being an innovative point of this paper.