| In the Filling mining is a green mining technology which is different from the traditional caving method.Compared with the latter,it has obvious advantages.It has important practical significance and strategic value to realize goaf filling by using bulk filling materials.Coal gangue is a solid waste produced in the process of coal mining.As a filling material,coal gangue has the advantages of wide source and low application cost.However,under natural conditions,granular gangue particles are mostly in a discontinuous state,that is,discontinuous gradation state,and are more common in geotechnical and mining engineering.The compaction and refracture characteristics of graded broken gangue determine the quality and effect of mined-out area under certain conditions.Therefore,in order to improve the utilization rate of rock and soil and realize the high quality filling of mined-out area,it is necessary to study the compaction characteristics of graded broken gangue.In view of this,this paper uses 0～25 mm gangue particles to prepare continuous graded and discontinuous graded gangue samples as the research object,and carries out the confined uniaxial compression tests under different loading rates and different discontinuous positions in the laboratory.The compaction deformation characteristics,particle size fractal and rebreaking characteristics,energy dissipation and crushing probability in the compaction-rebreaking process of graded gangue are taken as the research contents.The influence of axial stress,graded power index,loading rate and discontinuous position on the compaction and crushing characteristics of graded broken gangue is studied by using the research method of combining experimental research and theoretical analysis.A quantitative analysis method for the compaction and re-breaking characteristics of graded broken gangue considering discontinuous gradation is established.The energy dissipation in the process of compaction-rebreaking and the probability of grading crushing considering particle size migration are analyzed.The main research results are as follows:(1)Through the quantitative analysis of the compaction test results with different loading rates and different gradations,it is concluded that increasing the loading rate is beneficial to the compaction of the specimen,and the loading rate has little effect on the compaction characteristics of the broken gangue particles compared with the gradation,that is,the influence of the internal physical characteristics of the specimen on its compaction characteristics occupies the dominant position.(2)Based on the mathematical model of axial displacement and axial stress in the process of continuous grading compaction,the applicability of discontinuous grading is verified by the compaction test results.Furthermore,the physical meaning of parameters in the model was discussed by using the limit method,and the similarities and differences of compaction characteristics of gangue with different gradations were analyzed by using parameters,and the compaction constitutive model of broken gangue considering discontinuous gradation was established.The compression resistance of different grades under high stress is discussed.The compaction stage of graded gangue is divided into three stages:rapid compaction,slow compaction and stable compaction.(3)Combined with the particle size fractal theory,the influence of discontinuous position on the particle size distribution and its fractal characteristics in the process of crushing gangue with different gradations is studied,and the relative crushing rates of different gradations are obtained.Based on the research route of grading gangue from compaction to re-crushing and fractal evolution,the compaction and re-crushing model is established,and the physical meaning of parameters in the model is demonstrated,the internal relationship between grading compaction and re crushing is revealed,and the re crushing characteristics of different grading are further compared with the physical meaning of parameters.(4)Based on the energy dissipation characteristics of graded gangue in the process of compaction-re crushing,the correlation mechanism between energy dissipation and compaction and re-crushing of graded broken gangue is analyzed.The compaction stage of graded gangue is divided into low energy consumption stage and high energy consumption stage,which verifies the crushing boundedness of graded gangue.Based on the assumption of independence and uniformity of discrete element angle,the probability model of gradation crushing is deduced.Considering the particle size migration characteristics in the process of particle crushing,the crushing probability of gangue particles in different particle size ranges is obtained. |
PDF Full Text Request