Study On The Stability Analysis And Leakage Evaluation Of Wujiaotang Tailings Reservoir In Gejiu

With the rapid development of social economy,the demand for mineral resources increased significantly and the corresponding tailings output also increased.The place for storage of tailings is called tailings reservoir which refers to the necessary facilities to maintain the production of mines by means of dams or enclosures that are used to store metal and nonmetallic mines through tailings or other industrial wastes after ore sorting.Domestic and foreign research shows that once the tailings reservoir leakage,the surrounding environment will cause a very bad impact,threatening the people's lives and property safety,and this harm lasted longer,so in the process of operation,leakage problem can not be ignored.In this paper,the engineering geology and hydrogeological conditions of the Gejiu Wujiaotang tailings reservoir in Yunnan are described in detail by means of a large number of on-site surveys.Conbined with the analysis of water quality and leakage,the FLAC3D software was used to analyze the leakage of tailings reservoir caused by underground cave and the problem of surface leakage of tailings was analyzed by MODFLOW software.This paper evaluated and studied the leakage problem,which provided some guidance for the safe operation of the tailings reservoir and the guarantee for the safe living of the surrounding people.The main conclusions ofthis paper are as follows:(1)During the operation of the tailings reservoir,three leakage points have been found,but no tailings accidents have occurred along the fault zone in the past 8 years.The structures near the engineering area are mainly composed of the east-west structure,the northeast tectonic structure and the near-north-south tectonic group.The strata directly related to the engineering area are the second group(T2gb)of the old group,and the lithology is mainly dolomitic limestone.(2)The upper limit of the residual soil in the study area is small,the content of the coarse grain is low,and it has a heterogeneous support structure.It has been transformed into a watertight barrier near the impermeable under the load of the tailings.The effect of waterproof will become more and more obvious as the time increases and the thickness of the overburden is increasing.Under the action of the double barrier of tailings and residual soil,the amount of tailings that can enter the bedrock should be very small,and the pollutant content will be significantly reduced by the latter.(3)Under the condition of the same tailings reservoir's piling height,the diameter of the ponor has no obvious effect on the surface displacement of the tailings reservoir.Even the 1m-diameter hole may cause the surface to leak and form the leaking funnel.The influence of the ponor,the inclined shaft and the drainage tunnel on the stress field and the displacement field of the model is significant,that is,the leakage stability of the tailings reservoir has a significant effect,and the stress concentration of the hole is obvious.(4)Comparing the surface elevation of tailings with 2243m and 2255m respectively,it can be found that the average surface displacements of the tailings reservoirs above 1#?3#ponor are-0.113m-1.527m,+0.016m,respectively,and the surface displacements of 1#and 2#ponor are reduced when the tailings reservoir height increases.The surface displacement change of 3#ponor before and after the increase of the tailings reservoir' height is not obvious.The average displacements change of 1#?3#ponor,the five-stage inclined shafts and the five-stage drainage tunnel are 4.380m,1.889m,3.904m,-0.069m,0.453m,the displacement of the cave and the five-stage drainage tunnel are increased,and the displacement of the fifth-stage inclined shaft is not obvious.When the surface elevation of the tailings is 2243 m,the relationship between the surface displacement value above the ponor is 2#ponor>1#ponor>3#ponor.Besides,it is negatively related to the thickness of the red clay covered by the roof(hl#=9 m,h2#=4 m,h3#=12 m,)and the depth of the three water holes(h1#=13.328m,h2#=10.263 m,h3#=17.000 m).It also shows that the existence of clay layer has some curbing effect on the surface leakage of tailings.(5)In the case of the present elevation,the permeability coefficient of the residual soil is 10-6 cm/s,and the leakage quantity is 113.77 m3/d.When the permeability coefficients of the clay with the elevation of 2200-2220 m and 2220-2243 m are 10-6 cm/s and 10-5 cm/s,respectively,the leakage is 124.57 m3/d.When the elevation is 2255m,if the permeability coefficient ofthe residual soil below 2243m is 10-6cm/s,and there is no clay between 2243-2255m,the leakage quantity is 220.30m3/d.If the permeability coefficients of the clay of 2200-2220m and 2220-2243m high are 10-6cm/s and 10-5cm/s respectively,and there is no clay between 2243m and 2255m,the leakage is 233.26m3/d.If there is clay between 2243 and 2255m,and the clay's permeability coefficient is 10-6 cm/s,the leakage is 208.31m3/d.Ifthe permeability coefficient of residual soil between 2200-2220m,2220-2243m and 2246-2255m is 10-6cm/s,10-5cm/s and 10-4cm/s,respectively,the leakage is 230.71 m3/d.