Study On Process And Mechanism Of Seepage Failure Of Mine Waste Landslide Dam

The mine waste dam is a kind of dam body formed by artificially accumulating gravel particles into the channel during mining.Mine waste dam is generally composed of wide-graded non-viscous materials without effective reinforcement and anti-seepage measures.Percolation of the dam body is inevitable during the impinging process,and the percolation characteristics of mine waste dam determine the long-term stability of the dam body.In order to find out the effect of grading characteristics on the process and mechanism of infiltration failure of slag type dam.In this paper,Daxicha Ditch,Xiaoqinling gold mining area,Tongguan City,Shaanxi Province,is taken as the research area.Through the investigation of slag accumulation in the research area,the exploration of provenances,permeability experiment and laboratory model experiment,the permeability of mine waste dam body and stability of mine waste dam body are explored.The research results of this paper have great scientific and theoretical significance for further identifying the permeation failure process and mechanism of mine waste dams,and also provide test data support for future research on disaster prevention and reduction of mine waste dams.The results are as follows:(1)According to the permeability test,the influence of mixing characteristics and hydraulic gradient on the material permeability of mine waste landslide dam is analyzed.It is found that the material isopermeability has a strong correlation with porosity,while the nonuniformity coefficient Cu can only maintain a certain degree of correlation.Based on the analysis of the previous data and the existing test results,a formula for calculating the critical hydraulic gradient of mine waste landslide dam material under continuous gradation is presented.(2)The failure modes of the mine waste landslide dam in the test are mainly divided into two categories: one is the hybrid failure of the piping channel in the seepage process,which can be subdivided into the percolation-overtopping type and percolation-dam slope instability type,and the other is the failure of only overtopping type.The outburst process of mixed type is mainly:(a)the emergence of infiltration;(b)Generation and development of piping channels;(c)Release of sand-bearing water flow;(d)Collapse of the dam;(e)Overtopping overflow.The outburst mode affects the changes of discharge and severity during the outburst process.The peak discharge decreases with the increase of osmosis,while the peak severity increases with the increase of osmosis.(3)The influence of material permeability on the stability of the dam body is analyzed.According to the content of different particle groups,the analysis shows that when the ratio of coarse particle content to fine particle content is greater than 0.5,piping channels will appear in the failure process of mine waste landslide dam.According to the material structure,it can be divided into fine particle control type structure,medium particle control type structure and coarse particle control type structure.The percolation stability of the dam is affected by the content,material structure and uneven distribution in the dam.(4)Based on Geostudio software,the seepage field inside the mine waste landslide dam was numerically simulated,and the changes of pore water pressure at different water levels and different positions in the dam body were analyzed and compared.The maximum hydraulic gradient occurs at the foot of the water slope at the back of the dam and at the inlet of the upstream wetting line.