Study On The Correlation Between Coal Rock Damage And Macroscopic Deformation Based On Multi-fields Synchronous Monitoring

The deformation,failure and instability of the loaded coal rock are the macroscopic manifestation of the internal damage accumulation in the coal rock.Many scholars have studied the internal damage evolution law of the coal rock,such as electromagnetic radiation,acoustic emission and infrared radiation that released during the process of coal rock failure,and have achieved fruitful results.Because the internal damage of coal rock is difficult to be observed directly,this paper constructs a multi-fields synchronous monitoring experiment system based on machine vision and acoustic emission technology,and have studied the evolution law of the macroscopic deformation and internal damage of the coal rock materials during the loading deformation process,established the quantitative relation between the deformation and the damage,and realized the macroscopic deformation characteristics.Characterization of internal damage evolution of coal rock provides an important reference for monitoring underground rock and monitoring the early warning of coal rock disaster.The main achievements of this article are as follows:(1)The acoustic emission characteristics of coal rock under uniaxial monotonic loading are studied.It is shown that during the loading failure process of sandstone specimen,it will gather a large amount of energy in the process of loading and destroy the sandstone specimen,and release it quickly after reaching the limit,resulting in the instability and failure of the whole,and a large number of tiny micro cracks have been developed and expanded before the coal sample is completely destroyed.In order to quantitatively describe the internal damage of coal rock,a damage index model based on cumulative count of acoustic emission is proposed for quantitative description of the internal damage of coal rock.The CT scanning picture of samples before and after loading is digitized,and the ratio of fracture in different regions of coal rock samples is calculated and verified.The reliability of the damage index model is obtained.(2)In view of the inhomogeneity,continuity and sudden characteristics of coal-rock deformation,a monitoring system for macroscopic deformation of coal rock based on binocular vision is developed.The system hardware platform is formed by using two CCD industrial cameras,ring white light source and binocular camera support,and the system software platform is developed based on Visual C++.Through digital image acquisition,camera calibration,image preprocessing,binocular correction and 3D information recovery,the real-time,non-contact and full field monitoring of coal rock macroscopic deformation can be realized,and the cracks can be identified and extracted.(3)A multi-fields synchronous monitoring experiment system has been constructed to synchronize the acoustic emission of the damage field inside the coal rock and the macroscopic deformation field under the condition of uniaxial loading.Through the study of the correlation between the macroscopic deformation and the damage,the mathematical model of the macroscopic deformation and internal damage of the coal rock is obtained.The macroscopic damage characteristics are used to characterize the internal damage evolution of coal rock.