| The subsequent stage filling mining method has significant advantages such as good safety,high tailings utilization,large production capacity and low loss and dilution.The key to the successful application of this method is the stability control of the cemented tailings backfill of the mine room.Considering the filling cost and the stability of the backfill comprehensively,the cement-tailings ratio design of the backfill often adopts more than three proportions in the vertical height,and the stratification phenomenon will occur between the backfill of different proportions,resulting in the internal structure and the mechanical properties of the backfill become more complicated.Based on the sub project of national key research and development project"Theory and technology of spatiotemporal collaborative continuous mining in deep large ore block and multi mining area(2017YFC0602901)",taking the stage subsequent filling method of Daye Iron Mine as the research background,the layered cemented tailings backfill is taken as the research object.By means of laboratory experiment,theoretical derivation and numerical simulation,the failure mode,damage evolution characteristics,internal instability mechanism and strength model of layered cemented backfill are studied.(1)Based on the uniaxial compression test,the relationship between the uniaxial compressive strength,elastic modulus and structural characteristics of the layered cemented tailings backfill was quantitatively characterized by using different fitting functions.(2)According to the monitoring data of acoustic emission,the time-series evolution characteristics of the ringing count of the layered cemented tailings backfill are analyzed.With the aid of the acoustic emission positioning principle,the temporal and spatial evolution characteristics of the internal cracks in the layered cemented tailings backfill during the compression process are revealed.The instability and rupture of the cemented backfill has been effectively predicted.(3)Using the continuous damage theory and the principle of energy conservation,the damage constitutive equation of the layered cemented tailings backfill was deduced and constructed,and the constructed damage constitutive equation was verified;based on the experimental data,the structural characteristics of the initial damage of the LCTB specimen were quantitatively analyzed The influence of load damage and total damage evolution law,and the in-depth discussion of each fabric damage and total damage evolution law of SCTB specimens.(4)According to the actual occurrence of stope backfill,a three-dimensional numerical model of large height width ratio cemented tailings backfill considering the dip angle of slicing surface is constructed.The distribution characteristics of internal stress and displacement of exposed face under unilateral exposure are analyzed,and the instability mechanism of layered cemented tailings backfill in stope is revealed.(5)Based on Mohr Coulomb failure criterion,the strength model of sliding surface penetrating through the sub layer of front wall exposed and rear wall compression is established.The comparison and analysis with other strength models is made.It is concluded that the calculation results will be more accurate and reliable only by selecting the appropriate theoretical model combined with the actual situation of stope.(6)According to the spatial distribution characteristics of the rooms in Dayc Iron Mine,the actual strength requirements of the backfill are obtained by combining the theoretical and numerical calculation results.Based on the internal stress and displacement distribution characteristics of the backfill,the layered cemented tailings backfill structure is optimized and adjusted.Under the premise of ensuring the self-supporting stability of the cemented tailings backfill,the amount of cementing agent is reduced by about 20%,and the optimized backfill structure is optimized More reasonable. |
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