Study On Fine-grained Interlayers Heterogeneous And Coarse Particle Breakage Of High Tailings Dam

Tailings are the materials remaining after extraction and beneficiation of ores from the beneficiation plant.One common method for the disposal of tailings is to construct tailings ponds.In recent years,the amount of tailings that need to be disposal have increased year by year with the large-scale development of mineral resources.In addition,the surface area used to disposal tailings is restricted.Therefore,tailings dams have been forced to raise their height to store more tailings.The stress in the dam increases with the height of the dam for the high tailings dams.The strength of the tailings increases nonlinearly with the increase of confining pressure under high confining pressure.Therefore,the high dams are inherently less stable than low dams.Moreover,the hazards of failure for the high tailings dams are far greater than that for the low dams due to the fact that the high tailings dams store greater potential energy.Thus,the design,construction and operation of these high tailing dams call for a high level of care in engineering practice.In addition,most of the tailings ponds in China are constructed by wet-tailing stacking method.The layered or lenticular structures are formed during hydraulic deposition.The distribution and mechanical properties of lenticular structures weaken the stability of the tailings dam.Safety of high tailings facilities has become a widespread concern.Therefore,Study on interlayer heterogeneous properties and particle breakage of tailings under high stress were studied.It is important significance for the construction of new high tailings ponds or raise of existed tailings ponds.In this paper the heterogeneous occurrence law of sedimentary high tailings dam was aimed.Based on soil mechanics and particle crushing theory,combining laboratory tests,numerical tests and theoretical analysis,the effect of dipping interlayer on mechanical properties of tailings and the particle breakage of tailings under high confining pressure were studied.The main conclusions are as follows:(1)An improved sample preparation method was proposed.The tailings samples with interlayer at different dip angle were prepared.The consolidated undrained shear test(CU)was conducted on fine-grained interlayer specimens.The effect of dipping interlayer on mechanical properties of tailings were studied under low confining pressure and high confining pressure.The shear strength of tailings with interlayer decreases with the dip angle of the interlayer increases.The test results under low confining pressure and high confining pressure were compared.The similarities and differences generated by the stress factor are analyzed.(2)Based on the Coulomb theory,the principle that the sample with interlayer at large dip angle is prone to instability was explained.The results obtained in this study were verified from a theoretical perspective.From the perspective of the size and morphology of tailings,the mechanical properties of fine tailings are weaker than those of coarse particles.According to the deformation pattern of tailings,the deformation mechanism can be also divided into three types.(3)Using the principle of flexible servo,the constant confining pressure are maintained by the flexible particles.Numerical simulation of the samples with interlayer were carried out.The effect of dipping interlayer on the macro-microscopic mechanical behavior of tailings were studied.The deformation patterns of tailings with interlayers at different dip angles are analyzed.The distribution characteristics of the contact fabric by using the second order Fourier are quantitatively characterized.An obvious deflection in the principal orientation occurs for the samples with interlayer at large dip angle.The principal orientation trends to the direction normal to the interlayer.(4)The marked particle method was used to qualitatively study the particle breakage of tailings.The main modes of particle breakage of tailings are co-existence of crushing and grinding.The advantages and disadvantages of the existed particle breakage index are analyzed.It is concluded that Hardin's index and Einav's index are more reasonable.From the energy point of view,it is proposed that the specific surface area of particles is tested by using BET to quantify the particle breakage index.(5)Based on the principle of random multi-deformation,the irregular and crushable particle clusters of tailings were constructed.A new method is proposed to characterize the failure and deformation of the samples using shear fracture zones.Using acoustic emission technology methods,the evolution of micro-cracks was studied.Based on the first law of thermodynamics,the evolution of the crushing energy was analyzed.The number of particles breakage after test increases and the rate of change of particle breakage decreases with the increase of confining pressure.When the confining pressure reaches a certain extreme value,the number of particles breakage will not increase,and the particle size distribution of the tailings reaches stable.