Study On Mechanical And Acoustic Emission Characteristics Of Uniaxial Compression Of Cemented Tailings Backfill Subjected To Temperature

Cemented tailings backfill(CTB)with different depths of backfilling mining mines are subjected to different ambient temperatures.The damage and failure characteristics of the CTB subjected to temperature,which can be described by acoustic emission(AE)parameters,are closely related to the control of mine ground pressure.Taking Daye Iron Mine as the engineering background,the uniaxial compression and acoustic emission experiments of the unclassified CTB with cement-tailing ratios of 1:4,1:6,1:8,1:10 and 1:12,cured at the temperature of 20°C,35°C,40°C,45°C,50°C,60°C and at the curing time of 3 days,7 days,14 days,21 days,28 days,35 days,42 days,and 50 days,are conducted.The influence of temperature,cement-tailing ratio and curing time on mechanical properties and AE characteristics of the CTB are analyzed based on the obtained complete stress strain curve and AE parameters.The damage variable defined by the AE parameters is used to describe the damage evolution process of the CTB and the damage constitutive model of the CTB are established.The results are shown as follows:(1)The uniaxial compressive strength(UCS)and elastic modulus of backfill at 3days increase linearly.While the UCS and elastic modulus of CTB from 7 days to 50 days,which reach the maximum at 45 ?,increase gradually and decrease slowly when cured at 35 ?~45? and 45 ?~60 ?,respectively,as the temperature increases.The UCS and elastic modulus of the CTB at different temperatures and curing times increase gradually with the increase of cement-tailing ratio.Moreover,the UCS increase linearly with cement-tailing ratio.The UCS and elastic modulus of the CTB cured between 35 ? and 45 ? with different cement-tailing ratios increase gradually with increasing curing time,and the UCS shows logistic function relationship with curing time.The UCS of the CTB cured at 40 ? and 45 ?with different cement-tailing ratios reach the long-term strength at 42 days and 35 days,respectively.The UCS and elastic modulus of the CTB cured at 50 ? and 60 ? with different cement-tailing ratios increase at first and then decrease,reaching maximum at 35 days and 28 days,respectively,and the UCS fits quadratic polynomial fitting curve with curing time.(2)Higher energy AE events of the CTB prepared with different cement-tailing ratios and cured at different temperatures appear during the compaction stage,resulting in higher and concentrated ring count rate.when the CTB enters the elastic stage,the ring count rate has high volatility with the variation of temperature and cement-tailing ratio.The ring count rate is lower at yield stage and relative quite period appears before peak strength.While during the post-failure stage,a large amount of high energy AE events of CTB occur.The ring count rate,which increase first and then decrease,is higher and concentrated.The average value of the cumulative total ring count of the CTB increases first and then decreases with increasing temperature,and increases with the increase of cement-tailing ratio.(3)The damage process of the CTB under uniaxial compressive condition can be divided into initial damage stage,damage stable development stage,damage acceleration stage and damage failure stage.As the strain increases,the damage variable increase rapidly and is larger during the initial damage stage.While the damage variable increase slowly and the increment is smaller at the damage stable development stage.the damage variable shows accelerated growth and the increment is larger during the damage acceleration stage.When the CTB enters the damage failure stage,the increasing trend of the damage variable tends to be flat and the increment is small.The damage constitutive model of the CTB prepared with different cement-tailing ratios and cured at different temperatures are established based on AE parameters.The theoretical results using the proposed damage constitutive model agrees well with the experimental curves.