Investigation Of Mechanical Properties And Influencing Factors Of Layered Tailings Cemented Backfill

It is of great significance to carry out in-depth research on the filling engineering of tailings in the mining field,which is inevitably limited by the deep filling equipment in the mining industry.Based on the National Natural Science Foundation Project "Research on the unified theory and control technology of rheology,creep and solid fluid transformation of deep soft rock"(51674149),tailings cemented backfill specimens composed of tailings(aggregate),cement(cementing agent)and water were prepared in this paper.The tailings are taken from Gujiatai iron mine in Laiwu,Shandong Province,and the cement is the benchmark cement(P·I.42.5 silicate cement).Starting from the source,this paper fully understands the development of filling mining technology and finds the current shortcomings of this technology.On the premise of strictly complying with the technical specification for full tailings paste filling and other standards,this paper improves the preparation method of tailings cemented filling specimens.After curing for different ages under standard curing conditions,The uniaxial compression test and uniaxial creep test of tailings cemented backfill specimens with different influencing factors are carried out by taw-200 multi-functional material mechanics testing machine.Then the rebound method in the field of concrete is introduced and its reliability is verified,Finally,the uniaxial compression process of some tailings cemented backfill specimens is numerically simulated and analyzed by ABAQUS finite element software,which is verified with the test results.The main research contents and conclusions of this paper are as follows:(1)The preparation method of tailing cemented filling specimen is improved.The improved preparation method is easier to demould than the traditional preparation method.The obtained specimen is not only nearly free of damage,but also the physical and chemical properties are preserved to the greatest extent.the specimen is cured under the cover of release film,a more stable maintenance environment can be obtained.(2)According to the test scheme,the specimens of tailings cemented backfill are prepared and subjected to uniaxial compression test.The damage constitutive model of layered tailings cemented backfill is established.The mechanical properties of backfill is influenced by stratification phenomenon,cement sand ratio and the distribution of cement sand ratio in the upper and lower layers.The rough contact surface between layers will improve the quality of the cemented surface and improve the uniaxial compressive strength of layered tailings cemented backfill.The failure forms of cemented backfill specimens of tailings at each age are mainly tensile failure,and there are differences between low curing age and high curing age.The basic constitutive model of tailing damage is established by using Weibull strain theory.(3)The basic principle of rebound method is used to indirectly measure the hydration degree of cement in different parts of tailings cemented backfill.The results show that the hydration degree of different parts of the same tailings cemented backfill specimen is different,and the lower the curing age,the greater the difference.Combined with the test results,the failure form of the specimen is analyzed,and the reason for the failure form is explained from the perspective of material heterogeneity.The exponential function is more suitable for the strength measurement curve of tailings cemented backfill.The simple function model can well predict the variation of differential strength with hardness,and the quadratic function is the optimal model.(4)Uniaxial creep tests were carried out on some typical tailings cemented backfill specimens under graded loading.The test data are consistent with the trend of classical creep curve.The layered tailings cemented backfill with rough contact surface has better cementation effect between each layer.The isochronous curve method is used to calculate the long-term strength of tailings cemented backfill,and a more reliable result is obtained.The creep failure form of tailings cemented backfill is relatively single,which is tensile failure.Poyting Thomson creep model composed of basic elements can well predict the creep curve of tailings cemented backfill.(5)ABAQUS numerical simulation software is used to simulate and analyze the uniaxial compression test of some tailings cemented backfill specimens.The results show that the quality of stratification and cementation surface will affect the distribution of displacement.The uneven stress distribution at the end of the test piece of tailings cemented backfill.The true strain and plastic strain components of cemented tailings backfill are similar,and they are gradient distribution.The poor cementation surface will make the strain distribution of the upper and lower layers inconsistent.