# State-of-the-Art Research on Loess Microstructure Based on X-ray Computer Tomography
###### Abstract  
Computer tomography (CT), combined with advanced image processing techniques, can be used to visualize the complex internal structures of living and non-living media in a non-destructive, intuitive, and precise manner in both two and three-dimensional spaces. Beyond its clinical uses, CT has been extensively employed within the field of geotechnical engineering to provide both qualitative and quantitative analyses of the microstructural properties of loess. This technology has been successfully applied in many fields. However, with the rapid development of CT technology and the expansion of its application scope, a reassessment is necessary. In recent years, only a few documents have attempted to organize and review the application cases of CT in the field of loess microstructure research. Therefore, the objectives of this work are as follows: (1) to briefly introduce the development process of CT equipment and the basic principles of CT and image processing; (2) to determine the current state and hotspots of CT technology research based on a bibliometric analysis of the literature from the past three decades in the Web of Science Core Collection and CNKI databases; and (3) to comprehensively review the application of CT to explore the microstructural characteristics (such as particle size, shape, arrangement, and the connectivity, orientation, and pore throats of pores, etc.) and the evolution of structural damage in loess within geotechnical science. In addition, the progress and deficiencies of CT applications in the field of loess microstructure are summarized, and future prospects are proposed. loess; microstructure; CT scan; image analysis and processing; bibliometric analysis +
Footnote †: journal: Medical  
common methods for observing the microstructure of geomaterials include optical microscopy, scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and computed tomography (CT), among others. CT has been widely applied in the study of the microstructure of geomaterials due to its non-destructive, quantitative, repeatable, high-resolution capabilities and its ability to obtain the true geometric characteristics of particles and pores. Additionally, three-dimensional reconstruction and visualization provide strong technical support for the refined characterization of the microstructure of geomaterials [3; 4]. In recent years, a multitude of researchers have used CT scanning to construct the three-dimensional structure of loess, achieving a wealth of research findings. Considering the significance and broad application prospects of CT, as early as 1988 [5], [PERSON] in 2001 [6] and [PERSON] in 1999 [7] described in detail the principles and applications of computerized tomography. Building upon this foundation, [PERSON] [8] conducted an in-depth summary and elucidation of the specialized terminology that may emerge during the CT scanning process. It is worth noting that, possibly due to technological limitations in earlier years, their research was predominantly focused on rock and soil particles. Despite the inherent necessity of X-ray CT in visualizing granular geomaterials, coarse sand, or glass beads, its capacity to reveal the intricacies of soil structure and pore space distribution remains an area that requires further exploration. Consequently, conclusions derived from research based on idealized systems may not accurately reflect the characteristics of real soil [9]. [PERSON] et al. [10] offered a synthesis of the advancements in the application of CT in soil physics, yet their review was confined to applications pertinent to Brazil. The swift progression of computed tomography (CT) has broadened its sphere of influence, simultaneously introducing novel challenges to the methodologies of data acquisition and image analysis within the domain. The situation is especially evident as advancements in both hardware and analytical methods are made, and research questions in the field of geotechnical bodies become more complex and in-depth.