Mechanical Behavior And Acoustic Emission Characteristics Of Tailings Under High Stress

With the increasing demand of mineral resources and the limited use of land resources,it can be predicted that there will be more and more high heap tailings pond;at the same time,the progress of beneficiation equipment and technology will aggravate the fine-grained degree of tailings.The internal stress of tailings dam increases with the rise of dam height.The refinement of tailings particles and high stress environment has a significant effect on the stability of the tailings pond.In the past,the research on mechanical behavior of tailings was basically based on homogeneous materials and conventional pressure,but the systematic research on mechanical behavior of fine tailings under high stress is less.Therefore,according to the characteristics of high stress of large-scale high tailing dam,this paper carries out systematic research on the mechanical behavior and acoustic emission characteristics of high stress tailing dam by improving the laboratory experiment system of mechanical behavior of tailing under high stress and combining the laboratory experiment and theoretical analysis.The main research contents and conclusions are as follows:(1)Through triaxial compression,particle size test,micro scanning,micro image processing and other tests on the test tailings,the particle size distribution,mineral composition and particle characteristics of the tailings are analyzed.Based on the nonlinear mathematical model,the meso-scopic structure of the tailings is described,the strength evolutionary mechanism of the tailings under high stress is revealed,and the strength criterion of the tailings under high stress is constructed.(2)Based on the modified relative fragmentation concept * proposed by Einav,by comparing and analyzing the test results of tailings particle size before and after the test,the evolution law and fractal characteristics of tailings particle breakage are obtained.The mechanism of tailings particle breakage is revealed,and a prediction model suitable for the high stress of fine tailings particle breakage is constructed.(3)Based on the strength criterion of tailing under high stress and comparative analysis of the partial stress-strain relationship of tailings under different stress environments,the tailing constitutive model considering the stress term is proposed.The determination method of all parameters in the constitutive model is given.The physical meaning of the parameters in the model is clarified,and the applicability of the constitutive model under high stress is verified.(4)According to the theory of damage mechanics of rock and soil,the damage mechanics model and damage evolution equation of tailings are established.Based on the theory of continuous damage,which is the transition from the stable continuous strain field or damage field to the unstable state and the catastrophe theory,the starting condition of tailings failure is proposed,the starting point of tailings failure is defined and its rationality is verified.The formation mechanism of the starting point of tailings failure and its correlation with the shear expansion point is explored.(5)According to the synchronous characteristics of tailings deformation process and acoustic emission signal in time sequence under high stress,the change rules of acoustic emission parameters(acoustic emission impact,acoustic emission energy and other basic parameters and acoustic emission frequency band and fractal)in different bearing stages of tailings are explored.The frequency band energy distribution of failure start-up point signal and its adjacent points and AE correlation dimension of the signal is analyzed by wavelet packet frequency band decomposition method and G-P algorithm.The lowest point of correlation dimension and the highest point of energy percentage in the frequency range 62.5-125 can be used as the AE criterion of failure initiation point.The above research results are supposed to provide a theoretical reference for the study of performance degradation and dam break of large-scale high tailings dam.