Macroscopic And Microscopic Mechanical Properties And Creep Model Of Cemented Waste Rock Backfill

The mechanical properties of the cemented waste rock backfill directly affect the overlying strata movements and surface subsidence in the coal seam filling mining area.Studying the influence mechanism of the mechanical property of cemented waste rock backfill,exploring the non-destructive test method for the stability of cemented waste rock backfill,cognizing the microstructure evolution law of cemented waste rock backfill,analyzing the damage mechanism of the creep deformation of cemented waste rock backfill are the basic research topics on the safety assessment of overlying strata and surface structures in mining area,which have the important scientific significance and engineering value for safe and green coal mining.In this paper,the macroscopic and microscopic mechanical properties and creep model of cemented waste rock backfill were systematically studied by the research methods of experimental test,theoretical analysis and numerical simulation.The main results were achieved as follows.(1)The effects of the confining pressure,dosage of cementing material and gradation Talbot index of aggregate particles on the dilatancy characteristic parameters,acoustic emission response characteristics and compressive strength of cemented waste rock backfill were investigated through the uniaxial compression,conventional triaxial compression and acoustic emission monitoring experiments.The relationship contained eight decision parameters between the compressive strength of cemented waste rock backfill and the confining pressure,dosage of cementing material and gradation Talbot index of aggregate particles was established.The genetic algorithm for optimizing the decision parameters in that relationship was constructed.And then the space(four-dimensional space)visualization on the effects of the confining pressure,dosage of cementing material and gradation Talbot index of aggregate particles on the compressive strength of cemented waste rock backfill was realized.(2)The three-dimensional particle flow numerical model of cemented waste rock backfill was established by using PFC3 D.The crack evolution and particle fragment of cemented waste rock backfill under uniaxial compression and conventional triaxial compression were simulated.And the effects of the confining pressure,dosage of cementing material and gradation Talbot index of aggregate particles on the crack number,crack distribution and particle fragment mode were analyzed.(3)The ultrasonic response characteristics of cemented waste rock backfill were investigated through the ultrasonic detection experiment.The effects of the dosage of cementing material and gradation Talbot index of aggregate particles on the ultrasonic pulse velocity of cemented waste rock backfill were analyzed.The relationship between the compressive strength and the ultrasonic pulse velocity of cemented waste rock backfill was established.The model for predicting the compressive strength of cemented waste rock backfill was proposed.(4)The nonlinear visco-elastic-plastic creep model of cemented waste rock backfill was established through the tandem of nonlinear viscous dashpot,elastic-plastic component and Burgers component.The genetic algorithm for optimizing the seven decision parameters in that creep model was constructed.The three-dimensional form of that creep model also was deduced.The mechanism of the damage of cemented waste rock backfill caused by creep was analyzed.And the nonlinear visco-elastic-plastic creep model considered the damage was proposed.(5)The filling mining process of the coal seam was simulated by using FLAC3 D,which obtained the gradation Talbot index of aggregate particles of cemented filling material satisfied the optimal filling effect.The numerical model using the optimal cemented waste rock backfill under creep was simulated,and the time-varying evolution laws of the overlying key strata and surface subsidence in mining area was investigated.There are 124 figures,37 tables and 360 references in this dissertation.