Study On Acoustic Emission Characteristics Of Crushed Gangues During Confined Compaction

Gangue,as a kind of granular material,broke up under overlying strata pressure.The breakage of gangue affects the stability of backfilling materials or roadbeds.The energy produced by particle breakage is transmitted in the form of sound waves.The research methods used in this paper are field investigation,theoretical analysis and laboratory testing.In this paper,the acoustic emission propagation principle during confined compression is studied,and the macroscopic deformation mechanism of gangue is revealed from the microscopic view.Conventional confined compression tests were designed to test the compression deformation and crushing characteristics of gangue with different loading rates,aggregate gradation and lithology.According to the experimental results,the stages acoustic emission energy characteristics and the time-space evolution laws of crushed gangue under different compression conditions are analysed.Model between the macroscopic deformation of crushed gangue and acoustic emission energy is established.The main research results are as follows:(1)As the sample of crushed gangues continues to compact,acoustic transmission medium changes from three mediums to two mediums in steel cylinder during confined compaction.According to the number of propagation medium experienced by sound wave,three sound wave transmission states propagating,through two mediums of gangue-steel cylinder,through three mediums of gangue-air-steel cylinder,and through multilayerde mediums of gangue-air-steel cylinder,are determined.(2)Conventional confined compaction tests were designed to test the compression deformation and crushing characteristics of gangue with different loading rates,aggregate gradation and lithology.The change laws of macroscopic deformation and broken rate of gangue under different conditions are obtained.(3)The acoustic emission energy characteristics during compression are studied under different loading rates,grading and lithologic gangue conditions.Theacoustic emission energy under different conditions and stages is analysed.The research shows that acoustic emission energy increases with the increase of loading rate,the variation of acoustic emission energy characteristic changes under different stage and follows the rule that small-size gradation < large-size gradation,uniform gradation < non-uniform gradation,mudstone < mixed,gangue < limestone < sandstone.(4)The temporal and spatial evolution of acoustic emission in different stress states,stress stages,time and time stage is studied,and particle breakage at different stages is analyzed.The cumulative and stage events of acoustic emission change with stress and time.(5)The model between the macroscopic deformation and acoustic emission energy of crushed gangue is established based on the macroscopic deformation and acoustic emission variation characteristics of gangue.Linear correlations between macroscopic deformations and acoustic emission energy under different loading rates,gradations and lithologic gangue are obtained.