Experimental Study On The Acoustic Mission Characteristics During Uniaxial Compression Creep Of Fine Sandstone In Xiaolangdi Reservoir

In this paper,according to the results of conventional uniaxial compression test,uniaxial compression acoustic emission experiments are used to the fine sandstone of Xiaolangdi Reservoir with grading loading and respective loading by RLJW-2000 microcomputer controlled rock triaxial shear servo rheometer and PCI-II acoustic emission device.The creep properties and acoustic emission characteristics of rocks under two stress paths are studied.On this basis,the effects of different paths on creep acoustic emission characteristics of fine sandstone are compared.The research shows that:(1)Creep mechanical properties and creep model of fine sandstone under grading loading: Creep failure strength is 84.5% of uniaxial compressive strength.The generalized Kelvin model is used to fit the test results.The model that can better reflect the creep properties of fine sandstone and the corresponding model parameters are obtained.(2)Creep acoustic emission characteristics of fine sandstone under grading loading: There is a relatively obvious acoustic emission phenomenon in the creep process of fine sandstone,and the AE signal is directly related to the initiation,expansion and penetration of cracks.At the low stress level,the deceleration and constant velocity creep stages that the cumulative ringing count and cumulative energy curve rate of rock acoustic emission decreases with the decrease of creep rate;The high stress level is similar to the low stress level.The cumulative ringing count and cumulative energy increase are relatively large at high stress levels.(3)Acoustic emission characteristics of the creep failure stage under grading loading: rapid increase in amplitude,peak frequency,energy,and ring count is a precursor to creep damage.The quiet period of the acoustic emission parameters and the cluster growth before accelerating creep are the criteria for the precursor characteristics of creep damage;and the cumulative ringing count and cumulative energy curve variation characteristics of the accelerated creep phase are consistent with the creep curve.The inflection point of the cumulative ringing count curve of different creep stages is also earlier than the inflection point of the creep curve,indicating that the acoustic emission ringing count can sensitively predict the creep rupture and damage evolution of the rock.(4)The acoustic emission characteristics of rock creep under respectively loading: the increase of respectively loading energy is closely related to the increase of stress multiple.When the stress increases by a multiple,the maximum energy growth of respectively loading increases linearly;When the stress increases by an equal multiples,the cumulative energy multiple increasing becomes parabolic,revealing that the acoustic emission is closely related to the stress.(5)Creep mechanics and acoustic emission characteristics under different stress paths: the axial transient change with the graded loading creep is a linear change,but the respectively loading does not change linearly;the respectively loaded AE event number curve has a steeper slope,the grading loading is relatively smooth;the number of high amplitude and high peak frequencies of the grading loading is more than the respective loading,the explain that creep damage is an evolving process.