# CT Scanning of Structural Characteristics of Glacial Till in Moxi River Basin, Sichuan Province
## 5 Discussion  
Meso-structure and micro-structure play a decisive role in the physical and mechanical properties of rock and soil mass [33]. Therefore, it is of great significance to study the fine structure of rock and soil mass. However, for the acquisition of information on the meso- and micro-structure of intact glacial till, it is necessary to ensure that the intact structure of the soil sample is not damaged [34]. Because the soil and stone in the glacial till are mixed and the content of powder and clay is low, the cementation between the soil and stone is fragile and easy to break up; this makes it prone to sampling failure. As a result, there are few reports on intact glacial till so far. Therefore, the success of obtaining an intact glacial till sample is the key to analyzing the meso-structure and micro-structure of intact glacial till. The intact glacial till samples selected in this paper have excellent cementation properties, which provides the possibility for successful sample preparation. Advanced technology is the key to obtaining the meso-structure and micro-structure of intact glacial till. In recent years, with the development of computer technology and numerical calculation methods, a variety of methods have emerged in the field of analysis and research on the meso-structure and micro-structure of rock and soil [35; 36; 37], such as SEM techniques, statistical methods, fractal theory, and CT scanning methods. The CT scanning technology and scanning electron microscope technology used in the study of the meso-structure and micro-structure characteristics of intact glacial till are the most advanced methods for studying the structure of rock and soil mass. When statistical methods such as Monte Carlo, the stochastic method and Flac3D are used to simulate the meso-structure and micro-structure of rock and soil mass in 3D, their internal structure is extremely complex, because most rock and soil mass materials are composed of a certain size of high-strength rock block and relatively low-strength soil filling and corresponding pores. However, the three-dimensional meso-structures of rock and soil mass generated by these methods are all random simulations, which cannot truly reflect the real three-dimensional structure of rock and soil mass materials [38; 39; 40]. When the method of fractal theory is used to study and analyze the internal meso-structure and micro-structure, the rock and soil mass must be kept in their original state, and representative parts must be selected to reflect the structure during the sample preparation process; then, fractal theory should be used to perform fine measurement and digital representation of the internal structure of the loess, and further solve the structural parameters [41]. SEM technology is used to study the micro-structure of rock and soil mass. The sample preparation is simple. As long as the block or powder samples are slightly processed or not processed, they can be directly placed in the scanning electron microscope for observation, which is closer to the natural state of the material. The magnification has a wide range and high resolution, and can be continuously adjusted. Different fields of view can be selected for observation according to the researcher's needs. At the same time, under high magnification, high-brightness and clear images that are difficult to achieve by general transmission electron microscopes can be achieved. The sample can be observed with a large depth of field, a large field of view, and as a three-dimensional image [42]. It is possible to directly observe the rough surface with large undulations and the uneven metal fracture of the sample, so that people have the feeling of being in the microscopic world [42]. Because of the above advantages of SEM technology, it is favored by many scholars in the analysis of rock and soil micro-structure.