Variation Law Of Acoustic Emission Signal And Charge-induced Signal Under Uniaxial Compression Of Anisotropic Black Shale

Since the beginning of the 21 st century,human consumption of energy has become more and more rapid,and the demand for energy is difficult to balance.The current mining volume of coal and gasoline is far from being able to meet the development needs of our country,so it is imperative to exploit shale gas on a large scale.However,in the process of mining,due to the lack of a comprehensive and profound understanding of the mechanical properties of black shale,the recovery efficiency of shale gas has not reached a satisfactory degree,and the expected safe and efficient acquisition has been achieved.Therefore,the study of the anisotropy of sound-charge signal of black shale can provide corresponding theoretical support for the safe and efficient exploitation of shale gas.In this paper,according to the anisotropy of black shale with different dip angles,indoor uniaxial compression tests are carried out,the acoustic-charge signal monitoring system during black shale fracture is established,and uniaxial compression tests are carried out under different conditions.the change law of time domain signal of charge signal and acoustic emission energy signal is analyzed,and the damage variable of charge induction signal in the process of uniaxial compression cycle loading and unloading deformation failure is deduced.The characteristics of combined damage are analyzed quantitatively,and the results show that:(1)In the process of uniaxial compression of black shale with different dip angles at the loading rate of 0.05mm/s,there is a good agreement between the abrupt change of soundcharge signal and stress,and there is a concentrated stage of strengthening and post-peak breaking,and the peak signal often appears at this stage,and the change trend of the two signals tends to be the same.(2)When the loading rate changes from low-speed loading to high-speed loading,the time of generating high-value sound-charge signal for the first time is in advance,and it often occurs in the early stage of strengthening damage.When all the inclination samples enter the elastic and strengthening stage,a more dense sound-charge signal is formed,and the obvious stress drop phenomenon appears before reaching the peak stress,and the sound-charge signal with high amplitude appears at the same time.(3)The samples with different inclination angles have obvious charge signals during the first two cyclic loading,which proves that the black shale contains quartz and other piezoelectric materials.In the compaction stage,the friction between particles is large,which leads to the generation of charge signal.When entering the elastic stage,the amplitude change of the sound-charge signal under the cyclic load becomes weaker,which proves that the generation mechanism of the sound-charge signal is different.(4)When the number of cyclic loading and unloading is more,the damage variable calculated by the charge signal method shows a "ladder" increase,while the damage variable calculated by the acoustic emission energy signal method shows a "V" form.And,in this loading and unloading process,it is accompanied by damage.