Study On Deformation Characteristics Of Fine Tailings During Filling And Consolidation Using Geofabriform Method

Geofabriform method has received widespread attention due to its permeability to water and sand and low cost.It has gradually been applied to engineering construction such as tailings dam construction,providing a new idea for solving the difficulties of fine tailings dam construction.Compared to coarse grained tailings filling bags,fine grained tailings filling bags take longer to dewater and solidify,but there is not much research on the consolidation deformation laws of fine grained tailings filling bags.The consolidation deformation of fine grained tailings filling bags is also related to the settlement deformation and stability of the dam body built by the bags.Therefore,it is necessary to conduct in-depth research on the consolidation deformation characteristics of fine grained tailings filling bags.This paper takes the fine-grained tailings from the Shilei tungsten mine in Dayu,Ganzhou,as the research object.Using the method of combining indoor test and numerical simulation,through two stage experiments of geofabriform filling and consolidation,the effects of different filling concentration,filling height,and loading pressure on the filling and consolidation effects of geofabriform are studied;The process of geofabriform consolidation was numerically simulated and compared with mold bag consolidation tests;The numerical analysis of consolidation deformation of large size geofabriform in engineering was conducted,and the consolidation settlement laws under different geofabriform heights were studied.The main research results are as follows:(1)The effects of different filling concentrations and heights on the filling efficiency of geofabriform were obtained through mold bag filling experiments,and the changes of pore water pressure and geofabriform tension during filling were analyzed;The results showed that the filling concentration had a significant impact on the filling efficiency of the geofabriform,and both the pore water pressure and the geofabriform tension increased iteratively with the increase of the filling time.(2)After filling the geofabriform and entering the consolidation and drainage stage,it can be obtained by measuring the physical and mechanical properties of the tailings in the bag under different consolidation times.As the consolidation time increases and the filling concentration increases,the dry density,internal friction angle,cohesion,and compressive modulus of the tailings in the bag all show a trend of increasing;Under the same filling concentration and consolidation time,as the filling height increases,the dry density,cohesion,friction angle,and compressive modulus of the tailings in the bag decrease,while the deformation resistance of the mold bag consolidated tailings becomes weaker.(3)Through geofabriform consolidation tests under different loading pressures,it is found that applying a certain amount of loading pressure can improve the physical and mechanical properties of the tailings in the bag,and it has been proved that increasing the loading pressure is limited in improving the consolidation strength and resistance to deformation of the tailings in the bag.(4)The numerical simulation of geofabriform consolidation using ABAQUS software was conducted to study the changes in pore water pressure,deformation,and geofabriform tension during geofabriform consolidation under different filling concentrations and filling heights;Comparing and analyzing the measured settlement value of consolidation test with the numerical simulation settlement value,it is found that the simulated settlement value of geofabriform is in good agreement with the experimental value.(5)By simulating the drainage and consolidation of large size mold geofabriform in engineering,the changes of geofabriform displacement and pore water pressure during consolidation under different geofabriform heights were analyzed.The results show that the final settlement increases with the increase of geofabriform height,and the dissipation time of pore water pressure gradually increases with the increase of filling height;For large size geofabriform with a height of 0.4m,0.5m,0.6m,and 0.7m in the project,the time required to achieve a 90%consolidation degree is 33d,36d,43d,and 48d,respectively.If further improvement of the consolidation degree is required,the required consolidation time will be extended;The final settlement rate is around 24%under different geofabriform heights.(6)The hyperbolic formula is used to analyze the settlement of geofabriform under different consolidation times,and the t andt s_t under different influencing factors are plotted.The results show that the hyperbolic method can better reflect the change of geofabriform settlement with consolidation time;The final settlement prediction values of the mold bag under different filling concentrations,different filling heights,and different loading pressures were obtained;The hyperbolic method can be used to predict the consolidation settlement of bag dam construction projects.