Research On Macro And Meso Mechanical Properties And Failure Evolution Mechanism Of Cemented Tailings Backfill Under Dynamic Load

As the main load-bearing structure for ground pressure control in metal mines,the mechanical properties study of cemented backfill tailings(CTB)is significant.In addition,as a synthetic material,the presence of many internal pores and microcracks increases the complexity of the mechanical properties study.Meanwhile,the influence mechanism of blasting disturbance on the CTB mechanical behavior cannot be ignored.This paper takes the cemented backfill as the primary research object to reveal the mechanical properties,damage evolution process and mesoscopic properties of the CTB under dynamic load.And the macro-and meso-mechanical properties and damage evolution mechanism of CTB were investigated under dynamic load through indoor dynamic property tests,theoretical analysis and numerical simulation.The main results are as follows.(1)The dynamic compressive strength and macroscopic damage mode of the rock-backfill-rock(RBR)composite samples under different average strain rates were analyzed by the SHPB test.And the internal damage mode of the composite samples under low strain rate impact was investigated by X-ray computed tomography(CT)scanning technique.(2)The SHPB tests of the CTB samples were carried out to analyze the influence of the average strain rate and the confining pressure on the dynamic strength characteristics,stress-strain curves,energy dissipation and macroscopic rupture patterns of the CTB.The dynamic compressive strength of the CTB was quantitatively characterized as a function of the confining pressure and the average strain rate using different fitting methods.(3)The mesoscopic parameters such as porosity,pore size,crack volume and 3D fractal dimension of the CTB were investigated by combining CT scanning and 3D reconstruction techniques.The correlation mechanism with the dynamic macroscopic compressive was used strength was established.The morphology and distribution of the hydration products of the CTB were observed by scanning electron microscopy(SEM)tests,and EDS quantitatively characterized the content of each element in the hydration products.(4)A dynamic intrinsic model of the CTB considering the coupling effect of initial pore and confining pressure was established and verified by comparing it with the dynamic load test curve.The grid model of the CTB with initial pore space was coupled to the numerical simulation software to reproduce the whole process of the SHPB test and reveal the damage rupture evolution law of the CTB filler in time and space dimensions.(5)Taking the Daye Iron Mine as an industrial test background,combined with the three-dimensional numerical model of the CTB considering the dynamic parameters,the stability of the CTB in the stage of pillar mining was monitored.Feasible measures to enhance the CTB stability are proposed.