Experimental Study On Acoustic Emission Characteristics Of Rock Under Different Stress Paths

This article through to depot roof and floor bottom of Lake mine in two groups of sandstone and mudstone core,using theoretical analysis,laboratory numerical simulation of uniaxial compression test,and RFPA2D means on different stress paths of sandstone and mudstone of AE under uniaxial compression deformation process,according to the experimental data obtained in the evolution of AE features under the condition of loading in compression process of rock acoustic emission in the space,in order to analyze the changes of mechanical properties of rock deformation and damage,damage and failure modes of the comparison,this can forecast the failure of rock.(1)Under different stress paths,according to the different uniaxial compression test under the stress conditions of sandstone and mudstone,obtained that sandstone and mudstone in the failure process generally after the initial damage stage compaction stage,elastic stage,plastic stage and post peak,accompanied by an increase in uniaxial compressive strength of rock,the elastic modulus of rock specimen and the sonic velocity showed a increasing trend.(2)Analysis the different characteristics of acoustic emission of sandstone and mudstone under different stress path in the process of damage,the peak number of acoustic emission events of mudstone and the maximum stress of rock does not coincide,the peak number of acoustic emission events of sandstone and the maximum stress stress of rock coincide,AE energy get peak in advance compared with the peak AE events of sandstone,the number of acoustic emission events of mudstone and peak energy overlap.(3)Analysis the change of emission events and stress under the condition of cyclic loading and unloading process,the sandstone’s Kaiser Effect of feature points appears at the peak stress of 21%that is at the beginning of the feature in the elastic phase the mudstone’s Kaiser effect of feature points appear after peak stress.The Felicity effect of mudstone appears at 29%of peak stress.Through anglicizing amplitude parameters of acoustic emission,The change amplitude of unloading is 24 times of the loading time under the condition of rock loading and unloading,after unloading the activity of acoustic emission is more intense.The Felicity ratio of sandstone and mudstone decreases first,then increases and then decreases,it keeps less than 1 and the Felicity effect is notable.AE quiet period is not an essential property of rock,AE quiet period as the precursor of rock failure criterion,used in monitoring the stability of rock mass are not suitable for weak mudstone.(4)Under the condition of controlling stress,rocks occur the shear failure,in displacement control loading,rocks occur compressive-shear failure,and rocks occur tensile failure in cyclic loading and unloading.The lines of the acoustic emission points are in agreement with the splitting shape.(5)The numerical simulation of sandstone Aland mudstone B2 under different stress paths is carried out.The rock get micro crack,rock failure mode different from loading methods.Fragment size is also affected by the loading methods.The concentration of AE events occurred in the plastic stage,the peak stress was 90%,and the post peak damage stage was only about 10%.