Experimental Study On Temperature Effect Of Fly Ash Tailings Cemented Filling

In the design of traditional cemented filling process,when the mechanical strength,long-term stability,durability and transportation performance of filling materials are included in the research category,most of them are carried out under the indoor standard(constant temperature and constant humidity)conditions,and are affected by geothermal,geographical location,topography and climatic environment.The difference between the indoor environment and the in-situ environment faced by the mine filling material is large,which causes the temperature of the filling slurry to the goaf to change.In order to reveal and master the evolution law of the performance development of the filling body under the change of temperature(5 °C,20 °C,35 °C,50 °C).Taking the tailings cemented backfill with different fly ash incorporation as the research object,the systematic temperature effect test was carried out to study the backfill with excellent performance,economic applicability and technical feasibility.The main research contents and results of this thesis are as follows :(1)Through slump and bleeding tests,the flow characteristics and bleeding characteristics of filling slurry under different temperature effects were explored.The results show that the influence of different slurry temperature on the performance of fly ash cemented filling slurry is significantly different.With the increase of slurry temperature,the slump and bleeding volume of slurry mixture decrease significantly,while the addition of fly ash has no significant effect on the flow performance and bleeding performance of filling slurry,that is,the variability level of fly ash content is low,and the correlation between the two performance indexes of the slurry is small.In order to study the influence of fly ash content on the internal temperature-time history of slurry under temperature effect,the internal temperature of fly ash cemented filling slurry was monitored and the heat loss deduction diagram was made.It was found that the use of fly ash admixture instead of part of cement not only reduces the hydration reaction heat generation inside the filling slurry,but also the composite cementitious material can effectively reduce the temperature loss rate.The stable temperature in the early stage ensures the rapid growth of early strength to a certain extent.(2)In order to explore the mechanical properties of fly ash tailings cemented backfill under different temperature effects,96 cylindrical specimens of different sizes were made by orthogonal design method.The physical simulation tests of uniaxial compressive strength,Brazilian splitting and elastic modulus were carried out.The sensitivity and significance level of the influence of fly ash content,mass concentration and slurry temperature on the strength of backfill were analyzed by means of range analysis and variance analysis.(3)According to the analysis of multi-factor orthogonal test results,combined with the fluidity and transportation characteristics of filling slurry,based on the optimized test ratio,the mechanical strength test of fly ash tailings cemented filling body under different age-temperature conditions was carried out.The evolution law of compressive strength of filling body with the extension of curing time under different temperature conditions was explored.(4)In order to simulate the environment of in-situ temperature field in mined-out area,the backfill body was heated to different temperatures(30 °C,60 °C,120 °C,150 °C)for curing,and the influence of different temperature fields and heating time on the strength of backfill body was studied by thermal stability test.The research shows that in each temperature field,the strength of filling body decreases with the extension of curing time.Under the influence of temperature field,the strength of filling body with different slurry temperature shows that the strength of filling body with high slurry temperature is higher than that with low slurry temperature,and the greater the temperature field temperature,the more significant the effect.The adjustment of slurry temperature has a positive effect on resisting the strength loss of filling body at high temperature.