Research On The Resistance Of Gravel Piles To The Liquefaction Of Tailings In The Isolation Dam Foundation Of Yunxiniuba Huang Tailing Reservoir

Tailings reservoir is a huge dangerous source,and most of the tailings in the reservoir are harmful objects.Once the dam break occurs,the tailings deposits in the reservoir will rush out,which will not only destroy the surrounding ecological environment,but also pose a serious threat to the downstream residents.Therefore,the research work of preventing tailings dam break is of great significance.Niu Bahuang Tailings Reservoir of Yunxi Company,Gejiu City,Yunnan Province,Downstream of the Reservoir is Gejiu City and Kafang Town.The stock of the tailings pile in the reservoir is about 31,506,300 m3 and the dam height is 27.11 m,which is the third class reservoir.At present,the tailings reservoir has been closed.In order to improve the flood resistance ability of Niu Bahuang tailings reservoir,An isolation dam was built 350 m in front of the natural dam(homogeneous earth dam)of the tailings reservoir.The main purpose of the dam is to prevent the dam from temporarily retaining water after the damage of the drainage system under flood conditions,so as to gain a certain time for the repair of the flood control system of the tailings reservoir and prevent the dam break caused by the overtopping of the tailings reservoir,To ensure the safety of people's lives and property in Gejiu city.In this paper,the engineering background is that the foundation of isolation dam in Niu Bahuang tailings reservoir is strengthened by vibrating pipe sinking gravel pile.Using FLAC-3D software to establish the corresponding numerical model,the anti-liquefaction effect of gravel pile in tailings foundation is analyzed under the wave load of magnitude 7 earthquake,The results show that the liquefaction resistance of the tailings foundation strengthened by gravel piles is obviously improved,and the isolation dam will not be destroyed by liquefaction under the action of magnitude 7earthquake fluctuation load.The main contents and conclusions of this paper are as follows:(1)On-site investigation and sampling,the retrieved samples were subjected to a particle grading experiment,The internal friction angle and cohesion of tailings are determined by triaxial shear test in laboratory,the permeability coefficient of tailings is determined by permeability test,and relevant physical and mechanical parameters are provided for later numerical simulation.(2)FLAC-3D software is used to analyze the liquefaction of isolated dam foundation without gravel pile under the action of magnitude 7 earthquake fluctuation load.Through the arrangement of monitoring points at different depths of tailings in the lower part of the isolation dam,the maximum depth of liquefaction of the tailings in the foundation of the isolation dam is obtained to be 6 m.(3)With the help of FLAC-3D software,the liquefaction of the foundation of isolation dam strengthened by gravel pile is analyzed under the action of fluctuating load of magnitude 7 earthquake.The numerical simulation of pile group shows that the liquefaction resistance of the foundation of the isolated dam strengthened by gravel piles has been improved obviously under the action of fluctuating load of magnitude 7 earthquake.The isolation dam on the top of the gravel pile will not be destroyed by liquefaction of the foundation under the action of the magnitude 7earthquake fluctuation load.The numerical simulation of single pile is carried out to study the variation law of excess pore water pressure and excess air pressure ratio around gravel pile under the action of 7-magnitude earthquake wave load in tailings foundation.