Study On Mesoscopic Failure Process Of Non-homogeneous Granite Based On PDE Digital Image Technique

Rock Mechanics has been focusing on the mechanical properties and its failure modes.Previous studies mostly explored the failure mechanism of rock from macro-view and ignored the non-homogeneous properties of rock materials.Researches on rock failure mechanism by mesoscopic perspective has become new hot pot in recent years.Based on PDE image processing technique,setting up analysis model that can reflect real mesoscopic structure of granite.Through the finite element software ABAQUS,conducting numerical simulatin of Brazil Disk Split test,Uniaxial Compression test,Triaxial Compressiontest,the evolution rule and macroscopic response of mesoscopic crack in the processing of loading are studied.The main work is as follows:(1)Using camera to get the granite digital image,based on PDE technique C-V model and MATLAB programming to realize stable segmentation of the image.The digital information of the boundary point is obtained.AUTOLISP is used to realize the secondary development of AUTOCAD,automatically connectting the digital image point and setting up geometric model that can reflect the real mesoscopic structure.(2)Conducting the numerical simulation and laboratory test to analysize the procedure of Brazil Disk Split.Based on elastic mechanics analytical solution,the stress distribution rule of the points in parallel with vertical loading axis was obtained.The rule was compared with numerical solution of homogeneous rock and non-homogeneous rock respectively.The non-homogeneous of the components influence the internal stress distribution was concluded.Elastic-plastic analysis was followed by ABAQUS software,conducting Brazil Disk Split numerical test of non-homogeneous granite,the evolution rule of mesoscopic crack is conducted:the cracks started in the tensile region of disk's central part,approximately developed in parallel with vertical loading axis.The same conclusion as the real experiments can be testted.(3)In the numerical simulation analysis procedure of Uniaxial Compression test and Triaxial Compression test,we can get: cracks first sporacticly appear in the weaker components and medium interface for the uniaxial compression test.Cracks develop,gather and break through along the diagonal direction with load increasing.There are small areas of plastic zone around the main failure surface,which form branches of the crack.It performs shear and splitting failure form on a macro level.For the Triaxial Compression test,rock mechanical properties were affected by its non-homogeneous structure.The place of stress concentration first appeared in the quartz-mica contacting surface.When the tensile stress exceeded material's tensile strength,the mesoscopic cracks generated,scattered distributing inside the rock sample.The tensile stress wrap up the components of mica and feldspar with the external load increasing.And the compression stress was accumulated in the internal parts of these components.Cracks gradually became the main shear crack,gathering with the neighbor tensile crack.Eventually cracks gathered through each other eventually,and formed the macroscopic shear failure surfaces.