Damage Evolution Characteristics And Constitutive Model Of Fiber-reinforced Cemented Tailings Body

Waste-free mining has become an inevitable trend for the future development of the modern mining industry.A large amount of solid tailings waste is deposited in the tailings pond,which poses a serious threat to the surrounding ecological environment and security.The reclamation and large-scale utilization of tailings is the main way to eliminate mine solid waste on a large scale,and cemented tailings material has been highly concerned and widely used.By mixing tailings waste with cement to make cemented tailings materials,the environmental and safety problems caused by the accumulation of surface tailings can be effectively reduced and environmental pollution and geological disasters can be avoided.Mechanical properties and stability of cemented tailings materials have always been the focus of attention in the field of engineering.Different and complex engineering mechanical environments often lead to the overall performance of cemented tailings materials being reduced,which not only affects the quality of engineering applications but also poses security threats to personnel and facilities.Therefore,based on the National Natural Science Foundation of China project（No.51764013）,this paper investigates the damage evolution and constitutive model of fiber-reinforced cemented tailings materials from the damage mechanism of the materials,and provides a theoretical basis for the application and promotion of fibre-reinforced cemented tailings materials,to provide some guidance to promote the comprehensive utilization of tailings resources.The main contents and conclusions of this paper are as follows:（1）The effects of different slurry concentrations and cement-tailings ratio on the peak stress,peak strain,residual stress,elastic modulus,stress-strain curve,final rupture characteristics,and energy evolution characteristics of fiber-reinforced cemented bodies were discussed by studying the mechanical properties of fiber-reinforced cemented bodies under uniaxial compression.The addition of glass fibers was most effective in enhancing the peak stress and peak strain of the cemented bodies at a slurry concentration of 68%.With the increase of axial strain,the total energy and dissipation energy of glass fiber-reinforced cemented body specimens increased continuously,and the elastic energy increases first and then decreases with the node of peak strain.（2）The microscopic pore structure of the cemented body was tested by the nuclear magnetic resonance technique to study its pore distribution and fractal characteristics.The distribution curve of the transverse relaxation time T₂ spectrum of the cemented body showed a typical"three-peak"distribution,and the total spectral peak area was significantly correlated with the cement-tailings ratio and slurry concentration.The fractal dimension of the small pores of the cemented body was correlated with the cement-tailings ratio and slurry concentration,but the fractal dimension of the medium and large pores was not correlated with the cement-tailings ratio and slurry concentration.（3）The internal damage evolution of fiber-reinforced cemented body specimens was experimentally studied by acoustic emission（AE）technology,and the temporal and fractal evolution characteristics of AE parameters were obtained.Under the same cement-tailings ratio,the number of high-amplitude and high-frequency AE signals in glass fiber-reinforced cemented body is much higher than that in fiber-free cemented body.The temporal evolution characteristics of AE parameters of the cemented body specimens are significantly correlated with the cement-tailings ratio,and AE activities weaken with the decrease of the cement-tailings ratio.Under the same cement-tailings ratio,the mean ringing count correlation dimension of glass fiber-reinforced cemented body specimen is lower than that of fiber-free cemented body specimen.（4）Digital image correlation techniques were used to monitor the failure process of the cemented bodies with different cement-tailings ratios.By analyzing the full-field strain clouds and discussing the displacement changes of monitoring points,the mechanism of internal structure development and surface damage evolution of the cemented body is revealed.Under different cement-tailings ratio conditions,the maximum transverse displacement,maximum longitudinal displacement,and maximum full-field strain of the monitoring points on the surface of glass fiber-reinforced cemented body increase and then decrease with the decrease of cement-tailings ratio.（5）Since the traditional damage constitutive model ignores the influence of the initial compaction stage of the cemented body on the constitutive model,a modified damage constitutive model considering the initial compaction stage is established.Compared with the traditional damage constitutive model,the modified damage constitutive model can better describe the stress-strain curve characteristics of the whole process of the cemented body under uniaxial compression.After the damage extension,the damage of the cemented bodies with different cement-tailings ratios showed a monotonically increasing trend with the increase of axial strain and finally leveled off.The incorporation of glass fibers and the reduction of the cement-tailings ratio had similar effects on the damage evolution process inside the cemented bodies,i.e.,the damage extension was inhibited and the damage evolution process of the cemented bodies was prolonged.