Creep characteristics and constitutive model of cemented backfill considering stress and damage

In the filling mining method,the cemented backfill will have an important impact on the safe mining of the mine in a long term loading environment.Based on this,standard cylinder samples were prepared for uniaxial compression test,graded creep test and AE (acoustic emission) monitoring tests by the systems of WDW 100 kN microcomputer controlled electronic universal testing machine and DS2 series acoustic emission monitoring machine,and creep deformation and AE parameters,such as ring count,energy and amplitude,were obtained.Based on the results,the creep deformation characteristics and AE characteristics of cemented backfill under different stress levels were discussed.Compared with uniaxial compression tests,the creep failure characteristics of cemented backfill were revealed from a macro and meso perspective.Considering the effects of stress levels and damage,damage variable,a new secondary viscous body and switching component were imported to construct an improved Burgers model,which could characterize the creep rule of cemented backfill under different stress levels and was verified by experimental data.The research results show that ① Under different stress levels,the three phase creep deformation characteristics of cemented backfill are significantly different.Based on this,the load stress is divided into three types:deceleration,constant velocity and acceleration;② Under different stress levels,the AE characteristics of the cemented backfill are consistent with the changes in the creep deformation characteristics at each stage:during the deceleration creep phase,the AE events are more active;during the steady creep phase,there are fewer AE activities;during accelerated creep phase,AE events are most active;③ Compared with the failure of samples under the uniaxial compression,the creep damage of cemented backfill is relatively gentle.The main crack is deflected obviously along the propagation direction.Sample presents structural instability failure with integrity failure;④ The improved Burgers model constructed can be in good agreement with the experimental data of various stress levels,and it can better characterize the creep deformation rule of cemented backfill under different stress levels.