## 8 Conclusions  
This study comprehensively applies DIC and CT scanning techniques to conduct experimental research on the mechanical properties and cracking behaviors of three types of hole-fissured sandstone specimens under compressive loads after undergoing different numbers of wetting-drying cycles. Moreover, the influence of wetting-drying cycles on the energy of porous specimens is analyzed through energy evolution, and the following conclusions are drawn.  
1. The peak strength and elastic modulus of hole-fissured sandstone decreased with the increase in wetting-drying cycles and the expansion of the horizontal distance between pores. The damage degree of peak strength during the 0-10 cycles was higher than that during the 10-20 cycles, while the decline in the elastic modulus was more significant during the 10-20 cycles.
2. The primary cause of sample failure is the penetration of rock bridges between holes and fissures. As the number of wetting-drying cycles increases, the number and width of macroscopic cracks increase, and the left-right separation and fragmentation of hole-fissured sandstone become more pronounced, leading to a shift in the failure mode from simple tensile failure to tensile-shear failure and shear failure.
3. CT scan results reveal that with the increase in the hole and fissure horizontal distance and the number of wetting-drying cycles, the crack propagation path in hole-fissured sandstone evolves from a complex to a simpler form and forms a simpler crack network structure within the rock bridge region.
4. With the increasing count of cycles, the total energy of specimen failure, the total energy at the peak point, and the elastic strain energy all show a downward trend. The ratio of elastic energy consumption first increases and then decreases with the increase in strain. Abrupt changes in the elastic energy consumption coefficient over various cycles indicate the occurrence of crack propagation and instability failure within the sample.
5. In its natural condition, the surface of the sandstone appears comparatively even, with tightly packed mineral particles and no visible dissolution holes. After undergoing wetting-drying cycles, new holes and cracks become interconnected, causing the surface to appear scaly. The cementation between minerals is severely damaged, leading to a loss of structural integrity.  
P.L., validation, resources, writing--review and editing, supervision, and funding acquisition; P.J., software, validation, formal analysis, date curation, and writing--original draft; L.S., software, validation, and visualization; Y.P., validation and data curation. All authors have read and agreed to the published version of the manuscript.  
This research is funded by the Research Fund of The State Key Laboratory for Fine Exploration and Intelligent Development of Coal Resources, CUMT (SKLCRSM22 KF017).  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The raw data supporting the conclusions of this article will be made available by the authors on request.  
**Conflicts of Interest:** Author [PERSON] was employed by the company Postdoctoral Research Station of Shandong Huaning Mining Group Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.