Cyclic Deformation Characteristics Of Tailings Dam Under Freeze-thaw Cycles In Seasonal Frozen Soil Region

The cyclic effect of frost heaving and thaw settlement of tailings in seasonal frozen soil area makes the deformation characteristics of tailings dam in such a region different from other areas.How to ensure the safety of tailings dam in such a region with more scientific methods and means has become an urgent problem to be solved.The deformation characteristics of tailings dam under freeze-thaw cycles were studied by theoretical analysis,laboratory test and numerical calculation in this paper.The evolution mechanism of mechanical properties of tailings under freeze-thaw cycles was analyzed in macro and micro perspectives by studying the variation of physical and mechanical properties of tailings under different freezing and thawing cycles and the evolution model of mechanical parameters of tailings sand considering freezing thawing damage was established,which lays a theoretical foundation for the study of mechanical behavior of freezing thawing cycles of tailings sand.The effect of freeze-thaw cycles,freezing thawing temperature and freezing thawing time on the deformation of tailings dam was studied by similarity model experiment,and the degeneration law of tailings dam was obtained.The damage of tailings dam under freeze-thaw cycle with three field hydrothermally coupled mathematical models was established and the correctness of the model was verified by comparing with the experimental results.The safety factor and the quantitative degradation characteristics with the increase of freeze-thaw cycles were obtained by studying the distribution law of temperature field and displacement field of tailings dam under different freezing thawing cycles and different freezing temperatures and analyzing the relationship between maximum deformation and safety factor.In this paper,the stability of tailings dam in seasonal frozen soil area was deeply studied,and the deformation characteristics of tailings dam under different conditions were clarified,which provides theoretical basis and reference value for practical engineering.1.Study on variation law and mechanism of physical and mechanical properties of tailings under different freezing and thawing cyclesThe physical,mechanical and physical indexes of tailing sand were obtained by indoor particle analysis,water content,limit moisture content,compression consolidation,penetration and rapid shear test,cross plate shear and standard penetration test.The FST-200 three axis test machine was used to study the change law of compression modulus,permeability,water transfer,shear strength,cohesion and internal friction angle of tailings sand under different freeze-thaw cycles.The microscopic morphology and particle size distribution of tailings after different freeze-thaw cycles were studied by scanning electron microscopy(SEM).Based on the experimental results of physical and mechanical properties of tailings under freeze-thaw cycles,the mathematical model of physical and mechanical parameters attenuation of tailings sand considering freezing thawing cycles is established by introducing freeze-thaw damage factors.2.Model test study on deformation law of tailings dam under freeze-thaw cyclesThrough the independent research and development of tailings dam model test chambers that can provide multiple fields of temperature field and stress field,the experiment of freeze-thaw cycle model of tailings dams was carried out to obtain the deformation,internal forces,pore water pressure,moisture migration and other changes of tailings dam under different dam slope ratios,saturation line heights and freeze-thaw temperature tailings dams.The physico-mechanical properties of the tailings sand in the key position of the tailings dam were systematically studied after the freeze-thaw cycles.The comprehensive structural potential and freeze-thaw structure potential of the soil under freeze-thaw cycles were introduced to establish the freezing-thawing structural potential of the tailings dam under freeze-thaw cycle,and the structural evolution dynamics of the tailings dam in the freeze-thaw cycle was evaluated.3.A mathematical model of hot water coupling considering freezing thawing damage of tailings sand is establishedConsidering energy balance,thermal strain,convection thermal diffusion,conduction energy balance,heat conduction and other related laws,taking into account the relationship between unfrozen water content and temperature,phase change processing and other issues,through the tailings dam seepage field,temperature field,The stress field and other basic equations were used to establish the water-heat-force coupling model of the tailings dam under the action of freeze-thaw cycle.The numerical solution of the model was studied and compared with the model test to verify the correctness of the numerical solution and prove that the model can be applied.Study on Stress and Deformation Law of Tailings Dam under Freezing and Thawing Cycles.4.Deformation analysis and optimization selection of safety factor of tailings dam under freeze-thaw cyclesTo establish a numerical model for the freeze-thaw cycle deformation characteristics of tailings dam under different conditions,and study the maximum freezing depth,deformation field distribution and evolution law of tailings dam under different temperatures and different cycles of freeze-thaw cycles;based on the safety factor and deformation of the tailings dam.The quantitative relationship between the two,the law of safety factor degradation of tailings dam under freezing and thawing cycles was obtained.Based on this,the optimization of safety factor was carried out;the deformation regularity of tailings dam and the properties of tailings sand properties under the action of freeze-thaw cycles were comprehensively studied.The laws of change verify the relevant laws,mathematical models,and the accuracy and validity of numerical simulations obtained in the study.5.Deformation control measures of tailings dam in seasonal frozen ground areaCombining the actual engineering conditions in the seasonal frozen ground area,a three-dimensional numerical model of the tailings dam in line with the on-site geological conditions was established.The appropriate calculation parameters and boundary conditions were selected to predict the distribution and evolution law of the tailings dam deformation field under the freeze-thaw cycles.The geogrid technology was used to control the deformation of the tailings dam in the seasonally frozen soil area.By comparing the height of the tailings dam after dilatation,the change trend of the displacement before and after applying the geogrid and the change trend of the safety factor,the seasonal frozen ground area was proposed.The concrete measures for deformation control of tailings dams provide a theoretical basis for guiding on-site engineering.The paper has 81 figures,54 tables,and 186 references.