CT Image Processing And Mesoscopic Characteristics Analysis Of Freeze-thaw Rocks

The in-depth implementation of the "One Belt,One Road" strategy provides new opportunities for the development of my country's cold regions.With the continuous increase in the scale of geotechnical engineering in cold regions,the problems of rock damage caused by freeze-thaw cycles and freeze-thaw disasters caused by the decline in bearing capacity continue to emerge.Freeze-thaw disasters are one of the key issues affecting the stability of geotechnical engineering in cold regions.Therefore,the research background of this thesis is actual geotechnical engineering in cold regions,based on experiments,using image processing technology and statistical fractal theory to obtain meso-parameters that can accurately ch aracterize the internal structural characteristics of freeze-thaw rocks.In the framework of continuous damage mechanics,mesoscopic features are introduced into the macroscopic mechanical model,and the damage evolution behavior of the rock with the freeze-thaw cycle is systematically described.And on this basis,the finite element analysis software ABAQUS is used for multi-physics numerical analysis.The fresh red sandstone obtained by field sampling is processed into standard samples.The samples are divided into freeze-thaw group and CT group.With±20? as the temperature cycle interval,carry out the rock freeze-thaw cycle test first,and then the rock CT scan and mechanical property test after different freeze-thaw cycles are carried out to obtain CT images and macro-mechanical property parameters that characterize the mesostructure of the freeze-thaw rock.Through image processing technology,the acquired CT images are den oised,enhanced,binarized and three-dimensionally reconstructed to obtain two-dimensional images and three-dimensional digital models that clearly characterize the real mesostructure of the rock.Using fractal theory and statistical theory,the gray value,p orosity and fractal dimension of freeze-thaw rocks are statistically calculated,the mesoscopic damage evolution law of rocks under different freeze-thaw cycles is analyzed,and the rock freeze-thaw damage variable expressed by mesostructural changes is established.The freeze-thaw rock damage variables established above are introduced into the constitutive relationship that can reflect the macroscopic deformation and failure behavior of the rock,and the deformation characteristics of the residual stage are considered,and the rock damage constitutive model reflecting the whole process of rock deformation under the coupling action of freeze-thaw load is established,and compared with the test to verify the rationality of the model.Through numerical analysis software,the freeze-thaw cycle and uniaxial compression process of red sandstone are simulated,and the heat transfer effect of temperature under different freeze-thaw cycles and the stress-strain curve and strength distribution law of the rock under load are studied,and compared with the experiment.