Sensitivity Analysis Of Numerical Model Of Heavy Metalion Cu Migration In Tailings Reservoir’s Groundwater

The Tailings reservoir is an important environmental protection facilities of the mining industry, and performs very important functions in mine production and environmental protection system, such as regulating mines area of surface runoff, collecting the waste water produced in the process of containing mineral processing, protecting minerals which cannot be fully selected and so on. The heavy metal pollution in tailings will gradually migrate to the surface in the service life of the tailings reservoir, which will cause the environmental problems of the groundwater.In order to protect the local groundwater resources, I, in this paper, chose tailings reservoir of the Sichuan Li wu Copper Co. Ltd.1500t copper mining engineering as an example, through the analysis of the research in the area of natural geographical, geological, hydrological, environmental monitoring and other information, I established groundwater Cu migration model using Visual MODFLOW software, and analyzed the law of migration of heavy metal Cu. In order to improve the accuracy of the model, the sensitivity analysis of the model was carried out by selecting a series of representative observation values and parameters. The main conclusions are as follows:1. The results of Cu migration simulation:according to groundwater Cu migration model, In the trebling influence of ground water diffusion, topography and groundwater runoff, the pollutants Cu in tailings reservoir was migrated to the East and to the middle reaches of the complex terrain mainly. the complex terrain also was the design final stacking dam elevation. through the diffusion range, heavy metal dispersion scope was similar as the tailings reservoir shape, and with the passage of time gradually spread to the periphery, in the diffusion of groundwater flow field downstream of the heavy metal was greater than the scope of upstream, because the study area in central and southern was scarcity of groundwater, heavy metal in these two directions had no obvious diffusion.2. The results of sensitivity analysis:Based on MFI2K, the simple pretreatment procedure of MODFLOW, the results of sensitivity analysis which was related to the observed values and parameters were as follows:By the dimensionless scaled scaling sensitivity, it was concluded that the head observations hd09.ss was main sensitive factors, and head observation value hdOl.ss and flow observation value flow01.ss were the least sensitive. By the composite scaled sensitivity, it was concluded that HK₂, the permeability coefficient of the second aquifer was the main sensitive factor. By parameter correlation coefficients, it was concluded that if regression parameter estimation involved in the third layer aquifer permeability coefficient of HK₃ and regional recharge amount of RCH, parameter estimation results was not likely to be unique. And the results needed further analysis.The sensitivity analysis of model could be appreciated that the hydrogeological conditions Liwu Copper belongs to the mountains in the Kivu region of the mountain valley hydrogeological sub-region. If it was necessary to build, expand or rebuild tailings reservoir in the area which was similar to the regional hydro geological condition, in hydrogeology survey work should be possible to improve values observed in the highest water head area of the head, the second layer aquifer level permeability coefficient, the three layers of horizontal aquifer permeability coefficient and the amount of recharge area of these parameters accuracy, to reduced the uncertainty of the model structure and improved the reliability of the evaluation results.