# Study on the Influence of Moisture Content and Void Ratio on the Disintegration of Red Clay
## 3 Microstructure Analysis of Red Clay  
### Electron Scanning Microscope Test  
The scanning electron microscope (SEM) is a powerful tool for soil researchers as it provides a wide depth of field and strong stereoscopic effect, allowing for intuitive reflection of contact form and grain size of soil particles on the section. This facilitates the determination of microstructure morphology and microstructure parameters of soil [45,46]. Figure 2: Disintegration curves of various red clays in pure water. However, SEM is not suitable for quantitatively describing the size and distribution of micro-pores inside the soil, nor can it study the moisture content in the pores. Additionally, the sampling and drying processes can easily disturb the sample. In this experiment, red clay was prepared into soil material according to the designed moisture content and compacted for 24 h. Different void ratio reshaped samples were then made using the compaction method. The reshaped samples were slowly cut into small pieces of 10 mm \(\times\) 10 mm with a cutting knife and placed in a liquid nitrogen freezer for 30 min. After that, the samples were gently taken out with tweezers and vacuumed for 24 h to dry them. To reduce sample discharge, a layer of conductive material (gold) was uniformly plated on the surface of the soil samples. The samples were then placed in the scanning chamber of an S-3000N scanning electron microscope (SEM) for surface observation at a magnification of 10,000 times. Figure 3 shows SEM images of soil samples partially magnified by 10,000 times. The red clay exhibits granular, lamellar, block-like, flocculent, and debris structures. The soil sample with \(\omega\) = 24% and e = 1.0 consists of agglomerates of varying particle sizes, with less noticeable inter-aggregate pores. The agglomerates are closely connected in an edge-face and face-face manner, with poor arrangement orientation. The soil sample with \(\omega\) = 24% and e = 1.15 comprises agglomerates with larger particle sizes and clearer interfaces. The granular structure is prominent, and small soil particles fill the gaps between larger units. The agglomerates are in contact with each other in an edge-edge and edge-face manner, forming a flocculent structure with weak connection, loose structure, and local voids. In the soil sample with \(\omega\) = 26% and e = 1.0, layered and overlapped lamellar minerals are visible, along with local fine-grained structures. These lamellar minerals have good orientation and are mainly connected in a face-face manner. Fine-grained minerals are locally embedded in the lamellar structure, and the minerals are closely connected with poor pore connectivity. In the soil sample with \(\omega\) = 30% and e = 1.0, numerous block-like structures with different particle sizes and a small amount of lamellar structures are observable, along with occasional larger granules. The particles are mainly in face-face contact, and a certain amount of small and a few large pores can be seen, belonging to block-like structures. In the soil sample with \(\omega\) = 30% and e = 1.1, a large number of lamellar and flocculent structures are visible. The lamellar minerals are disordered with poor arrangement orientation, mainly in edge-edge contact, and some are in edge-face contact. The minerals have developed pores and good connectivity. In the soil sample with \(\omega\) = 30% and e = 1.15, block-like and debris structures are visible, with minerals mainly in edge-edge contact and some in edge-face contact. Large pores are well developed and filled with a large amount of debris internally. Figure 3: _Cont._  
Comparing a, c, d and b, f, when e = 1.0, the contact between red clay particles is mostly face-to-face contact; however, in the 24% soil, the particles are larger and the pore size is also larger, with locally visible holes and a loose structure. In the 26% and 30% soil, the particles are smaller and more uniform, the pore size becomes smaller, and the connection is also tighter.