Study On The Deformation And Damage Rules Of Coal Samples Base On Meso-mechanical Experiments

Recently years,the disasters of coal mine is more and more,under the complex conditions such as high ground stress,high gas pressure,low permeability and so on,with the coal mining gradually to the deep extension.The interaction between the various dynamic disasters highlighted and made the traditional prediction prevention measures is difficult.The new complex power disaster brings new problems of the coal mine safety production,monitoring and governance.Therefore,the new method is used to study on the relationship between macroscopic break of coal-rock mass and its internal meso-structure and defects,which is the focus of the study on the occurrence mechanism and prevention strategy of coal-rock compound dynamic disaster.In this paper,the microscopic structure of the coal sample and the acoustic emission characteristic during the loading process are taken as the main lines of the study.The macro-mechanics experiments,the microscopic experiments,the numerical simulation and the theoretical analysis were used to research the microstructure of coal samples.Under the different gas pressure conditions,the evolution characteristic of coal samples was analyzed,and the evolution process of internal cracks and damage in coal samples were studied by discrete element numerical simulation.The microscopic characteristics of coal samples were analyzed by X-ray diffraction,Scanning Electron Microscopy and Nuclear Magnetic Resonance,repectively.The corresponding results indicate that the degree of metamorphism of coal is inversely proportional to the meshing distance d_?002?;The characteristics of the primary pore and fissure structure of the coal sample are qualitatively observed,and obtained the typical microstructures of coal samples;the structural characteristics of the pore fissures were measured.The influence of gas on the mechanical properties and acoustic emission results of coal samples was summarized by mechanical experiments.When the Gas pressure increased to 2MPa,the strength of coal samples decreased by 37.57%,the elastic modulus decreased by 26.1%,the acoustic emission cumulative count decreased by32%,and the accumulated energy decreased by 25.32%.In general,the mechanical properties and acoustic emission results of coal samples are negatively correlated with gas pressure.The mesoscopic damage evolution of prefabricated cracked coal samples was studied by discrete element numerical simulation.It shown that the damage of the rock begins to rupture,and ends of the primary crack,and with the stress increases gradually,the microcracks were generated and aggregated,and became the main crack eventually.According to the results of experiments the room,the evolution model of coal samples damage and rupture based on acoustic emission parameters is established.The experimental results suggest that the relationship between the acoustic emission parameters and mechanical failure mechanism of coal samples.