Acoustic Emission Multiple Information Of Rock Mode ? Fracture Under Three-Point Bending Experiment

Tensile fracture is a common form of disaster in engineering rock mass,which plays an important role in the stability of rock engineering.In order to study the evolution law of acoustic emission(AE)characteristics in the process of rock tensile failure,argillaceous siltstone,granite,horizontal and vertical bedding marbles were taken as the research objects.AE test of mode ? fracture was carried out under three-point bending load.The time-frequency-space multivariate information of acoustic emission during mode ? fracture process was studied.The results are as follows:1)Time domain: The AE activity in argillaceous siltstone remains active throughout the whole process;the granite event rate drops rapidly after peaking before rupture,and energy releases sharply during rupture;the event rate of vertical bedding marble rises steeply,and the energy rate of horizontal bedding specimen fluctuates violently.2)Frequency domain: The number and energy of AE main frequency have obvious evolution trend at 40?60k Hz and 120?180k Hz,which can be used as the intrinsic frequency band of the test.In the later stage of loading,the proportion of energy in the middle and high frequency band gradually replaces that in the low frequency band.The diffusion of the dominant frequency from medium high frequency to intermediate frequency is the precursory information of fracture instability.3)Spatial positioning: Cracks in argillaceous siltstone form core regions at the loading tip;cracks in granite and vertical bedding marble accumulate in the fracture process area;under the influence of bedding,the cracks of horizontal bedding marble form shear fracture zones in the line connecting the two loading ends.After instability and rupture of the rock,tensile fracture occurred in all but the horizontal bedding marble.4)Evolution of fracture characteristics: According to the critical length,surface energy and energy conservation,the difference of AE is explained.By extracting AR value and energy,the crack mode and scale evolution are characterized.Finally,the damage evolution of fracture process is characterized by ring counting.Figure35;Table8;Reference 58...