Study On Damage Evolution And Constitutive Model Of Cemented Backfill During Deformation

Backfill mining method is more and more widely used for the high resource recovery rate and effectively preventing the collapse of surrounding rocks and ground subsidence,which meets the requirements of green mine construction.Cemented backfill(CB)plays an important role in backfill mining,and its failure is often caused by creep damage under long-term loading.Therefore,it is urgent to study the creep characteristics and constitutive model control to provide theoretical basis for the stability control of CB.First,the uniaxial compression test was carried out on cube samples of different sizes.By analyzing the changes of acoustic emission(AE)parameters and ultrasonic wave velocity,the basic mechanical properties and damage evolution rules of CB of different sizes were discussed.The results show that there is size effect on the strength and failure form of CB,and the AE and ultrasonic parameters also show a rule that changes with the size.Secondly,according to the study of the size effect of CB,the samples of the appropriate size were selected,and then the creep characteristics of CB were studied.Combined with AE monitoring,the creep deformation and failure characteristics under different stress levels were analyzed.It is found that the creep characteristics of CB are affected by the stress level,and the AE characteristics are consistent with the three-stage creep deformation characteristics;the creep damage of CB is relatively gentle,and sample present structural instability failure with integrity failure.Combined with ultrasonic testing,it shows that the creep characteristics of CB are affected by the stress level,and the AE characteristics are consistent with the three-stage creep deformation characteristics;the creep damage of CB is relatively gentle,and sample present structural instability failure with integrity failure.Finally,considering the effects of stress level and damage,the damage variables,new secondary viscous element and switching element were introduced to construct an improved Burgers model and its creep constitutive equation was derived.Verification of the model based on the sample results shows that the model better characterizes the creep deformation law of cemented backfill under the influence of damage degradation.