Study On Rock-mechanical Characteristics And Acoustic-emission Characteristics Under Different Confining Pressures State

During the construction of underground projects,the deformation and stress distribution of the rock does not occur and complete instantaneously,but is gradually adjusted over time.Based on this,this paper studies the rock-mechanical characteristics and acoustic-emission characteristics under different confining pressure conditions(Set the confining pressure of 10 MPa,the confining pressure holding time in three groups is 0h,0.5h,1h)around the confining pressure holding time.Take sandstone samples from an open-pit coal mine in Hami,Xinjiang,and cut,drill,grind,screen,and group the samples in the rock processing room.The rock sample is processed into a standard cylindrical specimen with a diameter of 50 mm and a height of 100 mm.The RTX-1000 triaxial test machine carried out triaxial compression failure experiments on rocks under different conditions of confining pressure holding time;and the PCI-2 type acoustic emission instrument was used throughout to monitor the rock sample acoustic emission signal.A large number of stress,strain,and acoustic emission data of rock samples under different confining pressure holding time were collected.And carry out analysis of rock sample deformation failure characteristics,peak strength,acoustic emission ring count rate,energy,acoustic emission b value,r value,acoustic emission peak frequency and acoustic emission relative quiet period.The effects of different confining pressure holding time on rock mechanical properties and acoustic emission characteristics are initially revealed.The main research results of this article are as follows:(1)The form of rock sample failure,peak intensity,etc.are related to the duration of confining pressure holding time.When the confining pressure holding time of rock samples is 0h and 0.5h,the form of rock failure is weak surface shear failure;when the conserving pressure holding time of rock samples is 1h,the form of rock sample failure is ductile failure.And,When the confining pressure holding time is maintained for 0h,the peak intensity of the rock sample is greater than when the confining pressure holding time is maintained for 0.5h;When the confining pressure holding time is maintained for 0h,the peak intensity of the rock sample is smaller than when the confining pressure holding time is maintained for 1h.(2)Acoustic emission ringing rate peak value,acoustic emission energy peak and acoustic emission peak frequency high frequency signal,The deformation stage of the three parameters is related to the duration of confining pressure holding time.When the confining pressure holding time is 0h,the three parameters mainly appear in the elastic deformation stage of the rock sample;when the confining pressure holding time is 0.5h and 1h,the three parameters mainly appear in the rock sample plastic deformation failure stage.(3)The relationship between the acoustic emission b value and the duration of confining pressure holding time is not clear.The study found that the rock sample acoustic emission b value curve will show a sudden drop at the peak stress point,This law can provide a reference for the prediction of rock instability and destruction in actual engineering.4)The change of r value of acoustic emission is affected by the duration of confining pressure holding time.When the confining pressure holding time is maintained for different lengths,the acoustic emission r value curve also changes,which can reflect the different types of rock sample failure.(5)The relative quiet period characteristics of acoustic emission are affected by the duration of confining pressure holding time.When the confining pressure holding time is maintained for 1h,before the rock reaches the peak stress,its relative quiet period generally occurs,and the relative quiet period lasts longer.