| The safe operation of the tailings dam has always been the focus of the mine and government departments.Once the dam failure accident occurs,this particular hydraulic structure will cause many casualties,property losses,and environmental pollution,and even bring long-term adverse effects on the local economic development and social stability.According to statistics,80% of the tailings dam failure accidents are caused by Seepage Damage and overtopping,and these two damage forms mainly occur in flood season.Therefore,it is of great engineering significance to explore the form and mechanism of tailings dam failure under flood conditions and master its development process for scientific management of tailings dam and prevention of accidents.Based on the engineering background of a tungsten mine tailings dam in Ganzhou City,Jiangxi Province,a 1:100 large-scale physical model test was carried out to explore the form of tailings dam failure and its damage development process under specific flood conditions.Simultaneously,the finite element analysis software MIDAS GTS / NX is used to analyze the two-dimensional seepage stress coupling of the tailings dam,and the strength reduction method(SRM)is used to calculate the stability of the dam.According to the two methods,combined with the relevant theoretical knowledge,the mechanism of dam failure is analyzed.Finally,the FLOW-3D software is used to simulate the dam failure discharge process,and the influence downstream range due to the dam failure caused debris flow is obtained.The specific conclusions are as follows:(1)The test is completed on a self-designed and built tailings dam test model,and it is concluded that the form of tailings dam failure under specific flood conditions is seepage failure,and the form of failure is flowing soil.The whole dam failure test lasted for 448 minutes and experienced two stages of seepage stability and flowing soil failure,each accounting for half of the total time.(2)Piezometers were embedded in the tailings dam model's four sub dams,and the pore water pressure values during the test were collected.The pore water pressure of sites 2,3,and 4 experienced a "linear growth-rapid decrease of growth rate-gentle / decrease" in each stage.Site 1 only showed noticeable linear growth in the second stage,and then the growth rate was low and kept stable.The rising rate of the height of the dam body's saturation line is faster in the early stage and slower in the later stage.(3)Considering the coupling of seepage and stress,the distribution law of seepage field and stress field in time and space is obtained by numerical simulation,which is in good agreement with the results of the physical model test;and the safety factor of tailings dam under different water levels is obtained.Based on the analysis of the strength reduction method(SRM)calculation results by using the criterion of instability judgment,it is known that the tailings dam is stable in structure without instability landslide when the reservoir water level is close to the dam crest.Combined with the model test,it is true that there is no slope instability in the dam body,but the dam failure will eventually be caused by the development of flowing soil to the breach of the dam crest.Dam failure is caused by progressive seepage failure.The safety assessment method of tailings dam based on model test and numerical simulation can fill the limitation of single research method,which is more objective and desirable.(4)FLOW-3D software is used to analyze the flow area,velocity change,and submergence depth of dam failure fluid in the process of flood discharge.Based on this,the emergency escape route of personnel is pointed out,and it is proposed that the reduction of flow velocity should not be regarded as the end of the whole dam failure flood discharge.According to the research conclusion,the prevention and treatment measures are put forward from two aspects of technology and management. |
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