Research On Damage And Destructive Mechanism Of Tailings Cemented Backfill At Different Saturations

The mineral resources of our country are widely distributed,and the number and distribution of underground metal mines are wide.The hydrological environment varies greatly between different mines or at different levels in the same mine.When the cemented filling body is often used as the key bearing structure,such as artificial pillar,roof and floor,it is often in different water bearing state.However,water is the key factor affecting the bearing performance of rock and concrete.In this paper,the cemented filling body of the tailings under the different water content gradient is studied.Based on the RMT-150 C rock mechanics test system,five sets of different saturation cemented backfill bodies were subjected to uniaxial compression acoustic emission test,and the damage evolution and strength characteristics of cemented backfill with different water gradients were explored.The action mechanism of water on the damage of cemented backfill body was analyzed by means of XRD and SEM mesoscopic test.The damage evolution of different saturation cemented backfill bodies was analyzed by the damage acoustic emission characterization and the damage constitutive model.(1)In different water content gradient,the cemented backfill body have different quantities between ettringite and C-S-H gel formation,resulting in the difference of cemented backfill microstructure,60% saturation cemented the ettringite,gel quantity higher,better attitude,the overall structure of the most closely filling body.Under low saturation,water scarcity inhibited the hydration reaction.Under high saturation,the ions generated by products and pore water further participated in the reaction,resulting in the increase of pore size,thus decreasing the structural tightness.(2)The process of damage and failure of cemented backfill body with different saturation is as follows:(1)primary microfracture compaction and closure;(2)Linear elastic deformation;(3)stable development of cracks;(4)convergence of rapid fracture development.With the increase of saturation,the peak strength,strain and characteristic stress value of backfill specimens show a downward trend,and the elastic modulus is increasing.Only 60% saturation cemented filling body is dense and stable because of its internal structure,and its strength is higher than that of other groups.With the increase of saturation,the cemented filling body is broken by the single inclined plane pressure shear,and the burst mode transition through the bar fracture mode to the saturation state.(3)The acoustic emission characteristics of different saturation cemented backfill bodies are similar to those of rock like materials.At the early stage,a small amount of acoustic emission signals appear,and the elastic stage is stable.The acoustic emission at the damage stage increases rapidly,and the instability occurs rapidly.The acoustic emission signal density of backfill body with high saturation is obviously smaller than that of low saturation sample.The increase of water content softens the cemented backfill body,and the water also inhibits the propagation of acoustic emission signal.The quantitative relation formula of the acoustic emission characteristic parameters to characterize the damage of the cemented filling body was established.(4)The constitutive models of cemented backfill under different uniaxial compression failure stages are obtained.The model is more accurate for describing the stress-strain relationship of the backfill body with higher saturation.(5)The acoustic emission parameters of backfill bearing damage characterization and damage constitutive relation based studies suggest that before the peak strength of cemented filling body with high saturation,the damage evolution is faster.Water promotes the damage evolution process of cemented backfill and accelerates the fracture damage evolution before failure.