Experiment And Numerical Simulation Study On Acoustic Emission Characteristics During Cracking Process Of Shale

Shale gas is a kind of unconventional oil and gas resource. The development of shale gas has profound significance for alleviating energy crisis. The mechanical property and the failure law of the shale are the key factors influencing the overall situation of mining shale gas. By monitoring the acoustic emission characteristics of the shale damage process, the development process of the shale cracks can be predicted.Using UTM5000 electronic universal testing machine and PCI-2 acoustic emission system, the uniaxial compression testing of shale from the Northern Jiangxi Province is made. The mechanics properties and acoustic emission characteristics of the shale in different regions and different bedding orientations are obtained and the difference between the mechanical properties and acoustic emission characteristics of the shale under the condition of uniaxial compression in different regions and different bedding orientations is investigated by the method of single parameters and correlation analysis. The acoustic emission characteristics of the shale under uniaxial cyclic loading and unloading are determined. RFPA2 D software was used to simulate the acoustic emission of failure process under the uniaxial compression and also to simulate the Kaiser Effect of shale under cyclic loading and unloading.The results show that the mechanical properties and the acoustic emission features of the shale in different areas and under the uniaxial compression condition have obvious differences. The compressive strength of shale is smaller, the stronger the acoustic emission activity in the destruction process and the greater the acoustic emission accumulative counts. The effect of bedding orientations of shale on the compressive strength and acoustic emission characteristic under the uniaxial compression is significant. Compared to the samples with 90°bedding orientations and 45°bedding orientations, the compressive strength of shale with 0°bedding orientations is the highest and the compressive strength of shale with 45°bedding orientations is the lowest.The AE ringing cumulative count and cumulative energy count of 0°bedding orientations is the largest in the whole process of deformation and failure, its AE count rate and energy rate is maximum and AE activity level is the strongest. The AE ringing cumulative count and cumulative energy count of 45°bedding direction is the minimum and the count rate and energy rate is the minimum. AE activity level is the weakest. Stress-time-acoustic emission energy efficiency figure is obtained by cyclic loading and unloading test and the exist of the Shale Kaiser Effect is verified right. The whole process of shale material deformation failure is simulated by the RFPA2 D and the location of crack and the extension process of the sample shale are imaginably shown by its acoustic emission figure. Kaiser effect of shale is verified by numerical simulation.