## 1 Introduction
Due to the multiphase nature and heterogeneity of soil [17], employing fractal theory to quantitatively depict soil structure and develop a fractal model can significantly enhance our comprehension of processes occurring within the soil structure. Consequently, fractal theory has emerged as a prominent topic in examining the microstructure of soil porous media. [PERSON] et al. [18] successfully utilized fractal methods to characterize soil pores, while [PERSON] et al. [19] applied fractal theory to investigate soil pores distribution characteristics. Further research by [PERSON] et al. [20] revealed that microscopic pores in soft clay exhibit pronounced fractal characteristics during consolidation, and [PERSON] et al. [21] confirmed the fractal nature of pores in saturated soft clay. These studies collectively underscore that soil pores exhibit fractal features. Various fractal models have been proposed to describe soil microstructure, including the Korcak island model [22], the Sierpinski carpet model [23], and its subsequent enhancements [24]. These models typically represent soil microscopic pores as a two-dimensional distribution. However, in reality,the adjustment of soil pore structure occurs adaptively in a three-dimensional space, and the distribution of pores within this space can be regarded as a dispersed system where pores are randomly distributed throughout the internal space of the soil. Thus, selecting an appropriate fractal model to accurately represent the characteristics of soil microscopic pores remains a challenging endeavor. The Menger sponge model [25], derived from the two-dimensional Sierpinski carpet fractal model, offers a fractal concept uniquely suited for illustrating the three-dimensional spatial structure of soil's porous system. In summary, to investigate the microscopic pore characteristics and mechanisms of disturbance damage in Zhanjiang Formation structural clay, unconfined compressive strength tests, scanning electron microscopy (SEM), and X-ray diffraction (XRD) tests were conducted on undisturbed samples and those subjected to various disturbance conditions. Using Arc Geographic Information System (ArcGIS), the three-dimensional visualization images of SEM microstructure were reconstructed to quantitatively analyze the evolution pattern of microscopic pores. Furthermore, a correlation analysis was performed to explore the relationship between unconfined compressive strength and microscopic pore characteristics. Drawing on Menger sponge fractal theory and the pore parameters obtained from the three-dimensional visualization images of SEM microstructure, the relationship between the macroscopic mechanical properties of Zhanjiang Formation structural clay and its pore fractal characteristics was elucidated. This analysis sheds light on the mechanisms of microstructural disturbance damage. The findings of this research will contribute to the understanding of the intrinsic microscopic mechanisms underlying the macroscopic mechanical behavior of Zhanjiang Formation structural clay, and provide valuable references for the evaluation of unconfined compressive strength in geotechnical engineering.