Study Of Sand Meso-fabric Based On CT Images

Sand is a typical granular material,and its anisotropy can be quantitatively measured by the pore direction distribution inside the material.In this paper,a virtual sectioning method based on three-dimensional reconstruction is proposed by combining image analysis and three-dimensional reconstruction technology.The pore direction distribution in granular materials is studied.Firstly,the mathematical principle of pore tensor analysis is introduced and deduced.Then,the original CT images of sand were analyzed and processed,and the serial cross-sectional images with clear grains and pores were obtained.Through the extraction and calculation of the microscopic parameters of sand,the scalar information of sand grains in each CT image was obtained.Two algorithms of surface rendering and volume rendering are respectively used to try to reconstruct three-dimensional sand samples.Among them,contour line algorithm and Marching-Cubes(MC)algorithm are used to reconstruct sand samples for surface rendering,and ray casting method is used to reconstruct sand samples for volume rendering.By comparing the results of commercial software ImageJ with the above methods,the Marching-Cubes algorithm is finally determined as the 3D reconstruction method in this paper.At the same time,the virtual cutting algorithm is studied and its feasibility is discussed.The commercial software and the program in this paper are used to cut the three-dimensional reconstruction body and extract the cutting plane respectively.The cut section is compared with the actual CT section at the corresponding position,and the microscopic information is determined to be extracted by the method in this paper.Three groups of sand orthotropic tests were carried out with the new method,and each group of test results were successfully obtained.After comparing and analyzing the results,the sample size was increased,and various meso-level information of the target sample was accurately obtained,including average particle area,total particle area,total particle perimeter,porosity,anisotropic amplitude parameters,etc.Finally,the three-dimensional pore tensor of the sample was calculated,and the experiment proved that the target sample had orthotropic anisotropy.