Fracture Test And Analysis Of Acoustic Emission Characteristics Of Rock-like Materials With Cracks Under Static-Quasi-Static Loading

In this paper,the RMT-150 B rock mechanics test machine is used to analyze the fractured body affected by the combination of loading rate and fracture dip angle by performing uniaxial compression tests on static to quasi-static,5 12.5 10 S--? ?5 15.0 10 S--? ?4 110 S--and4 12.5 10 S--? 4 loading rates of rock-like materials containing 0.1mm prefabricated fractures Breaking law of rock-like materials.Based on the acoustic emission test technology,the initiation law of rock-like materials with preset fractures under the combined action of loading rate and fracture dip angle was analyzed,and the dynamic frequency-domain characteristics of rock mass rupture during the whole process were also analyzed.The main research results show that:(1)The peak strength of rock-like specimens is affected by the preset fracture inclination angle and loading rate.At the same loading rate,the prefabricated cracks with different inclination angles have different degrees of damage to the compressive strength of rock-like specimens.The peak strength varies with the prefabrication.The increase of fracture dip angle shows a trend of decreasing first and then increasing,and it is the smallest when the dip angle is 45 °.When the fracture inclination angle is the same,the peak intensity of the fracture body increases with the increase of the loading rate.Different prefabricated cracks have different weakening effects on rock-like specimens.(2)There is a critical loading rate in the quasi-static loading range,which makes the loading rate enhancement effect no longer significant,that is,the growth of the fractured body basically stops after it reaches a certain value.This critical loading rate is around.(3)Under different loading rates,the degradation coefficient of rock-like specimens containing prefabricated fractures tends to increase first and then decrease with the inclination angle of the crack.The deterioration coefficient is the largest when the inclination angle of the fracture is 45 °and the smallest when the inclination angle is 90 °.The degradation coefficient of the fractured body at an inclination angle of 0-90 ° is between0-17%.At different loading rates,the degradation coefficient of the fractured body decreases with the increase of the loading rate,indicating that the larger the loading rate,the more the specimen's bearing capacity decays.The smaller.(4)Under the same loading rate,the elastic modulus of the fractured body increases with the increase of the inclination angle of the fracture.The elasticity modulus is the smallest when the inclination angle of the fracture is 0 °,and the curve of the relationship between the elastic modulus and the inclination angle generally shows a wave-like rise.The elastic modulus of the cracked body increases with the increase of the loading rate,and the rising rate tends to be gentle.The loading rate changes from4 110 S--increasing to4 12.5 10 S--? changing from static loading to quasi-static loading,and the increase of the elastic modulus is the smallest at this stage.(5)Acoustic emission activity became apparently active after the micro-crack closure phase of the specimen was completed.A large number of micro-cracks sprang up and formed macro-cracks after interpenetrating.The AE energy rate was most active before and after the peak.The characteristic parameters of the acoustic emission frequency domain varied with the loading process Change.(6)Acoustic emission test data shows that it is reliable to analyze the entire process of rock failure from the aspect of acoustic emission frequency domain characteristics.The energy initiation analysis can be used to obtain the crack initiation strength of rock-like specimens,and then the law of crack initiation stress intensity: At the same loading rate,the crack initiation stress level of the fractured body increases with the increase of the inclination angle;when the fracture inclination angle is the same,the cracked initiation stress level of the fractured body increases with the increase of the loading rate.Under static loading conditions,the fracture body with an inclination angle of 0 ° is about 60% to 70%,that is,about two thirds of the peak stress.With the increase of the inclination angle,the cracking stress level also increases.With the increase,the crack initiation stress level of the fracture body with an inclination angle of 90 ° under quasi-static loading conditions has exceeded 90%,and the crack initiation stress levels of the complete specimen in the static-quasi-static loading range have all exceeded 90%.