Study On Mechanical Characteristics And Damage Laws Of Coal Samples Under Different Loading

In recent years,with the increase of the coal mining depth and the speed of the working face,the coal wall gangs and rock burst have been aggravated,therefore,the influence of different loading rates on the mechanical properties and internal failure laws of coal samples is discussed,which provides a new idea for preventing and controlling the deep coal and gas complex dynamic disasters.From the microscopic angle of Tunliu coal pore fracture parameters,using RMT-150C rock mechanics test system with DS5 AE monitoring and signal analysis system,in the analysis of the mechanical properties and acoustic emission characteristics under different loading rates,and the evolution rules of AE counting,cumulative counting,energy,cumulative energy and coal sample destruction time at different loading rates were compared and analyzed;Secondly,the study simulated the destruction process of the coal sample?AE characteristics and mechanical parameters under different loading rates with RFPA^2D simulation software,finally,the damage theory was used to analyze the damage law of coal samples,a stress-strain constitutive model based on the damage of coal samples was established,and the conversion formula of the laboratory loading speed and the working surface speed was established.The main results of this paper are as follows:?1?The experimental results:The coal samples in Tunliu coal mine have a high degree of metamorphism,poor pore development,small pore diameter,and poor connectivity of pore fractures;With the increase of loading rate?0.0002⁰.2 mm/s?,the average compressive strength and elastic modulus of coal samples increased,while Poisson's ratio did not change significantly,among them,the compressive strength increased by 142.42%and the elastic modulus increased by 216.87%;Under different loading rates,AE counts and energy showed a gradually increasing trend,coal has obvious acoustic emission?AE count>100?time will be significantly ahead of schedule,but the coal sample values of AE counts and acoustic emission cumulative energy appeared a decreasing trend during the process of coal sample loading failure.?2?Numerical simulation results:As the loading rate increases from 0.0002 mm/s to 0.2 mm/s,the AE peak counting,AE peak energy,compressive strength,and elasticity models in the process of coal sample rupture showed a increasing trend,and the coal sample destruction and the initial acoustic emission signal time were also advanced,however,the cumulative number and energy of AE are decreasing,which was in accordance with the experimental results.?3?Model construction:The process of damage and evolution of coal and rock can be divided into 3 stages:initial damage,stable development of damage and accelerated development of damage,and the influence of loading rate on damage process is mainly manifested in the stage of damage stability.The research object of the rate effect in the field scale is determined as the speed of the working face,and based on the variational principle and strain equivalent,the conversion formula between the advancing speed of the work surface and the load rate in the laboratory scale is obtained:...