Research On Acoustic Emission Characteristics And Damage Evolution Of Tantalum-Niobium Ore Tailings Cement Backfill

Based on the National Natural Fund Project(No.51764013),in order to study the acoustic emission characteristics and damage evolution characteristics of cemented tailings backfill in tantalum-niobium mine,uniaxial compression and splitting failure acoustic emission tests were carried out on backfill specimens with lime-sand ratios of 1:4,1:6,1:8and 1:10,respectively.The deformation and failure characteristics and failure modes of backfill specimens during the whole loading process were analyzed.Through detailed calculation and analysis of B value of AE parameter and correlation fractal dimension value of filling body,the damage evolution of micro-crack initiation and propagation in filling body under different stress is further discussed.Finally,based on mechanical parameters obtained from uniaxial compression test and combined with damage mechanics theory,the tailings of tantalum-niobium mine are studied.The damage mechanics characteristics of cemented backfill are analyzed,and the following main conclusions are obtained:(1)Under uniaxial compression test,the filling body can be divided into four different deformation and failure stages,and the specimens with different lime-sand ratios show different failure modes.However,under the splitting test,there is no obvious yield stage of the filling body,and the failure mode is "symmetrical" linear splitting brittle failure along the axis of the specimen.(2)Under uniaxial compression,the maximum AE event rate and energy rate of most specimens occur in the early stage of compression or elasticity,and then rapidly descend to a lower level and fluctuate in a small range.Before the elastic stage of splitting test,the AE phenomenon is not obvious,only a small number of AE events occur;when the stress reaches the peak point,the AE event rate suddenly rises sharply to the maximum,at which time the AE activity is extremely intense.(3)In the elastic-plastic stage,the b-value of acoustic emission fluctuates greatly,accompanied by oscillation,and most of its minimum value or trough also occurs in this stage;before the stress level is 30%,the fractal dimension of filling body generally shows a downward trend,in which the minimum value of amplitude fractal dimension mainly concentrates in the range of 70% to 90% of stress level,while the minimum value of energy rate fractal dimension is mainly in the range of 70% to 90% of stress level.In the range of60%-90%.(4)Combined with the b-value and correlation fractal dimension,there is a decreasing trend,which can be used as a precursor of damage and failure of filling body.(5)Based on the mechanical parameters obtained from uniaxial compression test of filling body and damage mechanics theory,the results of filling body damage parameters suitable for this paper are obtained,and then the damage constitutive equation and damage evolution equation of tantalum-niobium tailings filling body with four lime-sand ratios are constructed.(6)Under uniaxial compression test,the larger the lime-sand ratio,the larger the damage value and the larger the specific energy of deformation when the stress peak is reached;and after the stress peak,the damage of the backfill develops relatively faster and the failure of the specimen is more sudden.