Study On The Stability Analysis Of A Tailing Dam Under The Action Of Rainfall And Earthquake And Seepage Enhancement Measures For The Dam Body

The stacking of tailings dams is a dynamic process,with parameters such as dam height,shape,and stability changing dynamically from the start of use to closure throughout the operating period.Tailings dams,as an important source of danger and pollution,once wrecked,will inevitably cause severe damage to people’s lives and property and the surrounding environment.A summary of numerous tailings dam disaster cases worldwide shows that rainfall is the most common cause of dam failure,and the second one is earthquakes.Therefore,it is of great significance to conduct research on the stability analysis of tailings dams under rainfall and seismic loading and to study the reinforcement measures to increase the seepage of the dams to ensure the regular operation of tailings dams,prevent dam failure disasters and ensure the sustainable development of mines.This paper takes a tailings dam in Fujian Province as the research object,combines the current theoretical knowledge about the relevance of tailings dams in terms of seepage and seismic at home and abroad,and analyzes the changes of the seepage field,displacement field,stress field and stability of the dam body under different rainfall intensities（50 mm/1d,100mm/1d,250 mm/1d）,different rainfall ephemeris（202 mm/0.5d,202 mm/1d,202 mm/2d）with the help of Midas-GTS finite element software.Meanwhile,the dynamic response,liquefaction region,dynamic safety factor,and dynamic stability of the dam body under the action of EI Centro seismic wave,Taft seismic wave,and artificial seismic wave are analyzed.Finally,the dam body is designed to be raised and expanded.The corresponding seepage enhancement reinforcement measures are proposed,and the change in stability of the raised dam body before and after seepage enhancement is analyzed.The specific conclusions are as follows:（1）With the increase in rainfall intensity and duration,the maximum negative pore water pressure value,negative pore water pressure area,infiltration line burial depth,dry beach length,average effective stress,and safety factor in the dam body will decrease.The maximum displacement in X direction and the range of displacement area at the top of the stacked dam will increase.Under the same rainfall conditions,the maximum negative pore water pressure occurs at the slope of the stacked dam,the maximum displacement in the x-direction occurs at the top part of the stacked dam,and the maximum average effective stress occurs at the lowest end of the middle part of the stacked dam.The safety factors of the dams under different rainfall conditions obtained using the strength reduction method are greater than the code requirements.（2）Horizontal peak acceleration in the middle of the stacked dam under seismic loading>horizontal peak acceleration at the top of the initial dam>horizontal peak acceleration at the top of the stacked dam.The maximum total displacements of the dam body under the action of the three seismic waves were 40.3 cm,46.3 cm,and 36.8 cm,respectively,with the maximum total displacements occurring at the upstream dam top location.The liquefaction area is distributed in the tailings of the upstream sediment beach,which is far away from the dam and has no significant impact on the stability of the whole dam.The safety coefficients of the dams under different seismic waves all show relatively large fluctuations.The minimum value of the safety coefficients of the dams appears within 1～2s after the arrival of the seismic wave crest.The dam’s acceleration response,displacement response,liquefaction zone results,and dynamic safety factor under the three seismic loads are all within safe limits.The dam will not be damaged under seismic loading,compared to the dam,which is most sensitive to seismic waves to Taft.（3）The ultrasound-based tailing sand permeability enhancement test showed that the permeability coefficients of tailing sands with permeability coefficient values in the range of10^-4,10^-5,and 10^-6 were enhanced by 12.5%,21.6%,and 21.1%,respectively,after the application of ultrasound to the fine tailing sand.For rainfall conditions,it is proposed to bury waveguide rods in the dam body to increase the permeability of the tailing sand by applying ultrasound to it to reduce the position of the dam infiltration line and thus improve the stability of the dam body.Under the 202 mm/1d rainfall condition,the dry beach length of the dam,the depth of infiltration line of the stacked dam,and the safety factor increased after the infiltration,which was 12.9%,12.3%,and 13.0%higher than those before the additional seepage.（4）For seismic conditions,it is proposed to apply the discharge field as a pressure slope to the dam reinforcement and to apply secondary pressure slope treatment to the dam body to achieve the purpose of seismic reinforcement.The peak horizontal acceleration at the top of the initial dam,the middle of the stacked dam,and the top of the stacked dam under the action of Taft seismic waves decreased significantly,and the reduction amounts were 62.3%,47.4%,and30.8%,respectively.The dynamic safety coefficient of the raised dam body is increased by about 21.4%and the location of the slip surface of the dam body becomes shallower after the soil drainage and slope compression reinforcement,which indicates that the soil drainage and slope compression strengthen the dam body has a specific effect.