Research On Multi-scale Catastrophic Mechanism Of Seepage Failure Of Fine-grained Tailings Dam

The fine-grained tailings dam has gradually become the future development trend in the field of tailings dam engineering.The group incidents threatened by dam failure downstream cause the security situation of the country and the industry to become more and more serious.The problem of disaster prevention and mitigation of tailings dams needs to be resolved urgently.In this paper,based on the study of the mechanism of the seepage damage catastrophe of the Chenkeng tailings dam in Makeng Mining,Fujian,the characteristics of the seepage and damage of the Chenkeng tailings dam are analyzed from the multi-scale study of the sample scale,mesoscale and engineering scale.The research method combining theoretical analysis,laboratory test and numerical simulation comprehensively analyzes the safety and stability of Chenkeng tailings dam.The engineering exploration method was used to obtain the sedimentation laws of the tailings in the Chenkeng tailings dam and the changes in the mechanical properties of the tailings sands of each sedimentary layer.Simultaneously,for the unevenness of deposition and high dam stress,different fine particle contents were simulated under the action of high stress Mechanical properties.Through the indoor small-scale seepage failure test and the medium-size seepage failure test,the phenomenon and law of the tailing sand samples with different fine particle content when seepage failure occurs are summarized.The CT scanning technology was used to realize the three-dimensional reconstruction of the fine-grained tailings microstructure,the establishment of digital image information,the analysis of the meso-structural characterization of the infiltration failure process of tailings sand with different fines content,and comparison of the macroscopic mechanical properties of the tailings sands The mesoscopic mechanism of different types of ore failure of ore sand;using fractal theory to analyze the damage characteristics of fine-grained tailing sand under different fractal dimensions,a criterion for determining the type of permeation failure of fine-grained tailing sand based on mass fractal dimension is proposed.According to the characterization changes of the mesostructure of the fine-grained tailings in the process of seepage failure,combined with the elastoplastic theory and the plastic damage theory,the elastoplastic damage constitutive model of the mesostructure of the fine-grained tailings during the seepage failure was established.The numerical embedding is realized through the ABAQUS subroutine.The numerical experimental results are compared with the actual undisturbed triaxial test data and the modified Cambridge model data,and it is found that the elastoplastic damage constitutive model has a better agreement with the undisturbed triaxial test data..According to the mesoscopic mechanism of fine-grained tailings infiltration failure,from the perspective of improving the mechanical properties of fine-grained tailings sand itself and the overall performance of the tailings dam body,physical and mechanical tests of flocculation of fine-grained tailings sand were carried out.The effects of different types of flocculants and curing agents have obtained the influence mechanism and combined optimization scheme of the key factors of flocculation coagulation of Chenkeng tailings dam.A three-dimensional model of the full-scale Chenkeng tailings dam was established.The FLAC3D software was used to analyze the operational seepage stability of the existing elevation and design elevation tailings dams under the conditions of drainage,stress,flocculant and curing agent.The influence mechanism of different combination optimization schemes on seepage stability is compared and analyzed,and the countermeasures for seepage damage prevention of Chenkeng tailings dam are proposed.