Study On Pore Structure Evolution And Seepage Dehydration Characteristics In The Process Of Full Tailings Thickening

Paste filling technology can achieve the dual goals of reduction treatment of mined-out area of metal mine and resource utilization of tailings,and achieve the effect of "one waste and two hazards".The research on paste filling is of great significance to promote the green development of mines.Paste and thickened tailings(PTT)technology has the advantages of water saving,dam construction safety and environmental friendliness,and can improve tailings treatment and filling operation.In the process of thick preparation,ultra-fine tailings particles are easy to form suspended water-locking flocs,which is seriously not conducive to the improvement of the underflow concentration of the thickener.At present,in the research on the stage of deep dehydration,the thick bed of full tailings inside the thickener is generally regarded as a "black box",ignoring the relationship between the meso-structure of tailings mortar and seepage characteristics.In this study,continuous dynamic thickening experiments and reverse seepage dehydration experiments on ultra-fine tungsten tailings were carried out,and the effect of rake frame shear on the concentration of underflow slurry was studied.With the help of high-precision CT scanning and SEM technology,the morphology and geometric structure of micro pores are analyzed,and the effects of pore structure and shear evolution of seepage channel on the dehydration performance of bottom flow slurry are studied by using three-dimensional reconstruction technology,and the thick dehydration mechanism of bottom flow slurry is revealed.(1)Continuous density test and rotary reverse seepage test were carried out.A small thickening test platform developed by ourselves can truly simulate the running state of the field thickener,which can study the evolution signs of the slurry under dynamic shear,obtain the compressed slurry at the bottom of the bed,and detect the permeability coefficient of the slurry.The physical results of slurry concentration and osmotic dehydration in different shearing stages are tested.it is found that shearing can increase the underflow concentration of the bed and reduce the permeability coefficient of the slurry.(2)The 3D reconstruction model is established with the help of CT scanning technology.By using the image processing software,the original grayscale image is processed,and it is found that the two-dimensional surface porosity decreases and the fractal dimension increases under the action of shear.Through the three-dimensional reconstruction software,the three-dimensional model of the characterization unit is established to truly reflect the internal information of the slurry.Based on the watershed algorithm,the pores and matrix are separated reasonably,and the pore structure is separated and calibrated,which is convenient for the quantitative characterization of the pore structure.(3)The evolution characteristics of pore structure in the process of shear are explored.Based on the analysis of the morphology and topological structure of pores,it is found that with the progress of shear,the porosity decreases,the pores become loose and broken,and the shear has a great influence on round and oval pores.The isolated pores are separated,the connectivity is determined,the equivalent pore network model is established,and the pore structure is analyzed quantitatively and qualitatively.It is found that under the action of external shear force,the large-size sphere evolves into several small spheres,and the sphere mainly plays the role of water storage,while the rod acts as water guide.(4)The characteristics of seepage and dehydration in water diversion channel are analyzed.Through the combination of physical experiment and numerical simulation,the macroscopic phenomenon of the water diversion channel is observed,and then the microscopic seepage channel is extracted,and the single-phase water seepage simulation is carried out.It is found that the tortuosity increases,the velocity and absolute permeability decrease,the absolute permeability is negatively correlated with the tortuosity,and the absolute permeability decreases with the increase of curvature.Finally,the water diversion path and mode of the seepage channel are explored,and the formation and annihilation mechanism of the water diversion channel are discussed.(5)Engineering application was carried out.The experimental data and theory are applied to the reform of thickener in a tungsten mine.Through the design and reform of the rake structure,the dewatering efficiency and the stable underflow concentration are improved.In order to solve the engineering problems of high overflow concentration,difficult overflow water treatment,low and fluctuating filling slurry concentration,high filling cost and so on,the theory is better transformed into practice and the paste thick filling theory is enriched.