Experimental Study On Strength Characteristics Of Full Tailings-cemented Filling Body/layered Cemented Backfill

In this paper,based on the demand to construct a full tailings cement filling system in a lead-zinc mine in Hunan Province,the strength characteristics of the full tailings cemented filling body/layered cemented backfill were studied based on the characteristics of the filling system and the filling method.This paper draws the following conclusions through laboratory experiments and theoretical analysis.(1)Study on rheological properties of full tailings cement slurry.Filling slurry flow performance is the basis for studying whether tailings can be used for conveying and filling.The rheological properties of the full tailings cement slurry under different mass concentrations and cement-sand ratio were tested by MCR52 modular rheometer.The rheometer measured the viscosity and shear stress of 20 groups of different proportions,and carried out the experiment of the expansion of each group.The author analyzes and establishes a one-factor and two-factor nonlinear regression model.The viscosity and yield stress of the slurry increase with the increase of the slurry mass concentration and the cement-sand ratio.The degree of expansion directly reflects the flow properties of the slurry.The cement-sand ratio of slurry and mass concentration have a general quadratic function relationship with their viscosity and yield stress.When the mass concentration of the slurry is between 76% and 78%,the slurry will not be isolated and precipitate,and the fluidity is good.(2)Experimental study on uniaxial strength of full tailings cemented filling body.The author conducted a uniaxial compression test on 20 sets of test blocks of different ages.It was found that the sand-sand ratio of the same filling body follows a quadratic function relationship.The mass concentration and age follows the S-function relationship with the strength of the filling body.The greater the cement-sand ratio of the filling body,the greater the effect of increasing age on the strength of the filling body.The smaller the cement-sand ratio,the slower its strength with increasing mass concentration.The author establishes a binary quadratic regression equation of the strength of the filling body with its sand-cement ratio and slurry mass concentration.The regression effect is good and can be used for the prediction the strength of the filling body.When the mass concentration of the slurry is between 76% and 78% and the cement-sand ratio is between 1:4 and 1:8,the flow performance of the filling slurry is the best,and the 28 d strength of the filling body can meet the actual production work requirements.(3)Experimental study on the strength of the layered cemented backfill of the full tailings.The limitations of the filling process lead to discontinuity and instability of the filling process,which causes the filling body to stratify.The authors conducted uniaxial compression experiments on a total of 30 groups of different ages of fillings with different layers,interval time,concentration difference between layers,and dip between layers.The author analyzes that the stratification quantity corresponds to the quantitative relationship of the strength of the filling body in accordance with the power function model.The interval of the stratification time corresponds to the quantitative relationship of the exponential function.The increase in the number of layers and the interval of stratification have the effect of weakening the strength of the filling body.The difference in the concentration between the layers also reduces the strength of the filling;When the inter-layer inclination is increased,the strength of the stratified filling body is first increased and then decreased.The uniaxial compression failure modes of stratified backfill under all stratification factors show longitudinal splitting failure,but the uniaxial compression failure modes under different stratification factors are different.In the filling process,the filling concentration and the stability of the cement-sand ratio should be controlled as much as possible to reduce the influence of the stratification effect.