Grading Loops And Uninstall Sandstone Creep Pcm Sound Emission Characteristic Research

Acoustic emission (AE) is one of the important monitoring methods of rock mass failure. AE characteristic during rock mass failure under different loading was researched massively now. The failure of rock mass is closely related to time, creep of rock is the important reason of rock mass failure. Therefore establishing the relationship between creep and AE has important values in theory and application. Based on theoretical analysis and test, the main content and conclusions are as follows:(1) The AE theoretical model of creep damage was established, which revealing the AE characteristic during creep fracture and steady creep. AE has three stages including attenuate, steady and accelerated corresponding to the deformation. The percentages of AE show attenuate, fluctuant and sharply raised. AE activities are centered on the accelerated creep stage with increasing of rock homogeneity degree.(2) The deformation and young’s modulus were analyzed through the sandstone test under step-cyclic loading and unloading. Parameter identification of creep model was study and parameter of viscoelasticity of rock was obtained due to particle swarm optimization, then creep damage was investigated based on them. The differences of rock deformation mainly reflect on the stages of creep. The stiffness of rock was raised after creep and unloading. The elastic parameters, viscoelastic modulus and viscoelastic coefficients of creep model depend on instantaneous deformation, deformation of attenuate stage and time enter steady creep.(3) The change law of AE was obtained through analyzing the change rate and accumulation of parameters of AE. AE characteristics under different stress levels were studied, the mechanism of creep damage was revealed. Frequency of AE at the stage of creep is lower than it at the stages of loading and unloading, strength of AE at the high stress levels is higher than it at the low stress levels.(4) Based on fast fourier transform, the characteristics of AE under different stress levels were investigated. Subdominant frequency phenomenon emerged from every cyclic loading and unloading. Frequency range became wider with the increasing of stress level.(5) The fractal features of AE time series during creep were investigated, and the relationships between fractal correlation dimension and time under different stress levels were obtained. Fractal correlation dimension fluctuate steadily with time under the same stress level, AE during creep is relative uniformity. Fractal correlation dimension increases with the increasing of loading. Frequency and strength of AE have positive correlation with loading.