Experimental Study On Mechanical Characteristics Of Graded Tailings Cemented Backfill Under Static And Dynamic Loads

With the increasing mining depth in recent years,the probability of accidents in mining areas such as collapse of empty areas and instability of roadway deformation has increased,and tailings filling has become one of the most popular methods for filling composite aggregates.This method can not only effectively limit the land.Pressure activity,and is conducive to tailings treatment and environmental protection in the mining area,but the problem of filling body damage also threatens the safety of mine production.Deep filling bodies are affected by underground static pressure and blasting and earthquakes.It is imperative to study the factors of filling body damage.Therefore,this paper mainly studies the change of mechanical properties of static and dynamic filling bodies with the curing age and the lime-sand ratio as the variables that affect the performance of the filling body.The main conclusions are as follows:(1)Under uniaxial compression,the age of curing increases,the strength of the filling body increases,and the initial period is almost linear growth.The growth trend is gradually flat at 28days;the ratio of sand to sand is increased(1:8,1:6 to 1:4).The overall performance shows a fast and slow growth trend;when the ratio of lime to sand is 1:6,the growth of the filling body is relatively high.The bigger the age,the greater the influence of the filling body on the sand-cement ratio,and the strength growth mainly occurs in the later stage of curing.In the production,attention should be paid to the protection of the early filling body to avoid damage to the filling body caused by the blasting event;the elastic modulus of the filling body increases with the increase of the sand-sand ratio,and the rate gradually increases,and the elastic modulus increases from 3 days to the curing age.The change is larger in 7 days.When the growth is 7days and 14 days,the elastic mode is closer.At 28 days,the growth rate becomes larger again,and the growth trend is almost the same as the intensity.The damage constitutive equation is derived by the theory of strain equivalence.The same lime-sand ratio is obtained.As the curing age increases,the peak damage degree of the filling body increases,and the strain in the compaction stage decreases.At the same age,the ratio of lime to sand increases,and the damage corresponding to the compaction stage and the yield limit stage will improve in degree.(2)Under the condition of single dynamic impact,the curing age increases,the dynamic load strength of the filling body increases obviously;the sand-sand ratio increases,and the dynamic load strength of the filling body increases;the ratio of sand to sand is 1:8 and 1:6.The static load strength of different curing ages is lower than the dynamic load strength;when the ratio of sand to sand is 1:4,the static load strength of the low age(3-7 days)is greater than the dynamic impact velocity(2m/s);The dynamic strength of the backfill under different curing agesincreases with the increase of strain rate,and has a good strain rate effect.The filling body is affected by the strain rate during the curing period from 3 days to 14 days,and tends to be stable at 28 days.Under different lime sand ratio and curing age,the dynamic strength improvement factor increases linearly with the increase of strain rate.At the same age,the ratio of lime to sand increases,the dynamic linear coefficient increases first and then decreases,and reaches the maximum at 14 days.When the temperature reaches 28 days,the strength of different sand-sand ratios of the filling body tends to be stable.Once again,as the curing age increases,the growth trend of the filling body strength decreases.With the increase of the curing age,the ratio of sand to sand is 1:6.1:8 intensity change coefficient increases first from 3 days to 14 days,and starts to decrease significantly at 28 days.At 1:4,the linear coefficient shows a decreasing trend.With the increase of the strain rate,the absorption energy of the filling body increases with the ratio of lime sand to sand and the age of the curing age.The absorption energy of the sand-sand ratio is1:6 and 1:4.During the curing period from 3 days to 7 days,the increase was the largest,while the sand-sand ratio increased from 1:8 to 1:4.During the same age period,the absorption energy increases,and the larger the lime-sand ratio,the more energy is absorbed by the filling body.(3)Under multiple dynamic impact conditions,the incident energy increases and the number of impacts decreases;with the incident energy,the peak stress increases with the increase of the number of impacts,and the overall trend of “increasing-decreasing” is the same as the ratio of sand to sand.Compared with the sand-ash ratio,the curing age increases,and the filling body experiences an increase in the number of impacts,but the peak strain is less affected by the incident energy and the number of impacts.;the incident energy is about 30% of the critical incident energy,and the initial blasting impact increases the dynamic strength of the filling body.The dynamic strength of the filling body decreases until it breaks;when the incident energy is less than the critical incident energy of 48.3%,the dynamic strength increases with the number of impacts.When the incident energy is greater than 70%,the dynamic strength of the filling body decreases until it breaks;Extending the age of maintenance and reducing the incident energy can increase the number of impact resistance of the filling body;the filling failure mode is at low speed and low age,and the multiple impact filling body failure points mainly occur at the end,and the filling increases with the increase rate.The body crack develops and mainly penetrates the crack until it is destroyed.Therefore,in actual production,the unit consumption of the explosive is reduced as much as possible,the end treatment of the filling body is strengthened,and the effective roof formation is performed.Red layer thereby reducing damage to the filling body.