Study On Mechanical Characteristics And Damage Evolution Of Coal-Rock Mass Under Different Loading Rates

In the process of coal mining,due to different coal seam and mining technology conditions,coal or rock mass is often affected by different loading rates that is caused by mining-induced stress,tectonic stress and construction disturbance.In this paper,stress transfer test of different loading rates was carried out by mining-induced stress testing machine,and uniaxial compression tests of gypsum materials and cement mortar materials at different loading rates were carried out by using hydraulic servo rigid testing machine.And with the help of particle discrete element analysis software,the construction of uniaxial compression model and related numerical simulation analysis were carried out,and the damage constitutive model was built by acoustic emission evolution law.From the perspective of macro and micro analysis method,the mechanical characteristics,acoustic emission rule and damage evolution relationship of coal and rock mass are analyzed and studied.(1)In the process of uniaxial compression,the acoustic emission law of coal and rock mass is mainly experienced by 3 periods.Number of acoustic emission signal is small during the compaction and elastic period,and the nun1ber of acoustic emission increases abrupt in the stage of fracture instability,and the number of signals in the residual phase of the specimen is reduced.(2)During stress transfer test of different stress loading rates,the failure characteristics of the specimen and the acoustic emission parameters present a distinct phase rule.Maximum ringing count of the corresponding region is decreasing,and the cumulative ringing count of the acoustic emission is most obviously more than 3kN/s when the velocity of transfer is 1kN/s.during the transfer of stress at different speeds of 1 kN/s,3kN/s and 5kN/s,(3)The effect of loading rate on acoustic emission signals of coal and rock material is significant.With the increase of loading rate,the acoustic emission rate is obviously increased and the acoustic emission activity is more intense.(4)The greater the loading rate,the more concentrated the damage to a certain macro fracture surface,and the failure form changes from a multi macro fracture to a single macro fracture surface,and the degree of overall fragmentation is reduced.(5)The damage evolution process of coal rock specimen can be divided into initial stage of damage,the stage of damage stable development and the stage of damage accelerating development.The effect of loading rate on damage development mainly shows the stage of damage stability,that is,the greater the loading rate,the smaller the strain value is,and the strain range is smaller.