Specific Energy Characteristics Of Cemented Tailings Backfill Of Damage And Fracture Under Uniaxial Compression

Cemented tailing filling mining method is more and more widely used in China's underground mines,especially metal mines.The instability of cemented tailing backfill threatens the safe production of mines.The damage and fracture process of backfill is essentially the process of energy conversion between backfill and the outside under external loads.Taking Daye iron mine as the engineering background,the uniaxial compression and acoustic emission(AE)experiments of unclassified backfills with cement-tailing ratio 1:2,1:4,1:6,1:8 and 1:10 are conducted to explore systematically the energy change characteristics of the damage and fracture process of backfills.The mechanical properties and AE characteristics of different cement-tailing ratio backfills are analyzed based on the obtained stress-strain curve and the AE parameters.The damage variable which is defined by the AE parameters is used to describe the damage state of backfill.The specific energies of backfill with different cement-tailing ratio are calculated based on stress-strain curves,whose characteristics and relationship with the damage variable are analyzed.It can provide guidance for the mine to determine the damage status of the backfill according to the energy parameters and to select a reasonable cement-tailing ratio.(1)By analyzing the test results,the uniaxial compressive strength and elastic modulus of the backfill decrease with the decrease of cement-tailing ratio,while the poisson's ratio decrease with the increase of cement-tailing ratio.The AE events are active during the compaction and yield phase,which is quiet during the elastic phase.The lower cement-tailing ratios are,the more active the AE events are during the post-failure stage.(2)The damage process of the backfill can be divided into initial damage,stable development of damage,rapid propagation of damage and damage-failure stage.The damage variable increase rapidly during the initial damage and the yield stage,and increase slowly during the stable development of damage and damage failure stage.(3)The total specific energy and the dissipative specific energy increase with the increase of the axial strain,while the elastic specific energy increase first and then decrease with the increase of the axial strain and achieve the maximum value when the backfill reaches the yield strength.The total specific energy,elastic specific energy and the dissipative specific energy increase slower during the compaction stage.The elastic specific energy increase more rapidly during the elastic stage compared with the yield stage.The dissipative specific energy increase more rapidly during the yield stage and the post-failure stage compared with elastic stage.When the backfill reaches the yield strength,the total specific energy,elastic specific energy and the dissipative specific energy grow as the cement-tailing ratio grows.(4)The total specific energy and dissipative specific energy of backfill increase with the increase of damage variable.While the elastic specific energy increases first and then decreases with the increase of the damage variable.The lower the cement-tailing ratio,the smaller the decrease rate of the elastic specific energy.The damage state of the backfill is closely related to the dissipative specific energy.The dissipative specific energy presents an exponential relation with the damage variable approximately.The dissipative specific energy can well reflect the damage state of the backfill.