## 5 Conclusions  
In this study, a uniaxial real-time CT scanning ultrasonic high-frequency vibration excitation test was conducted on a brittle fine-grained red sandstone sample. The test was designed to examine the properties of rock microfractures by analyzing real-time CT scans taken during vibrational excitation. Additionally, digital image processing techniques were utilized to examine the formation and growth of holes and cracks in the sample. The primary findings are as follows:  
1. Under the stimulation of high-frequency ultrasonic vibration, the maximum crack propagation depth in red sandstone reaches 32.15 mm, with the highest crack development degree in the uppermost rock layer. The total crack length extends to 119.63 mm, and the maximum crack opening value reaches 1.287 mm. The excitation surface edge serves as the crack initiation zone, with the fracture propagating radially towards the free surface, forming a fracture surface. The adjacent fracture surfaces are connected, resulting in local rock failure;
2. The original CT image's grayscale interval was equalized, and the image was nonlinearly stretched to enhance the contrast between the matrix and the pores and cracks within the rock. Subsequently, threshold segmentation of the processed image was performed using a trial-and-error method to isolate the pores and cracks in the CT image section. Ultimately, the solid porosity of the red sandstone was determined to be 6.18% when the image segmentation threshold was set at 0.06, which is consistent with the MRI test results;
3. The application of digital image processing technology was utilized to quantitatively determine the attenuation characteristics of the influence of ultrasonic vibration excitation on rock pore and fracture development with respect to rock depth. The porosity of the CT section in proximity to the excited surface demonstrated a significant increase of 170.42%, whereas that of the lowest CT section experienced a marginal increase of only 0.22%. This suggests a positive exponential relationship between the porosity increment and rock depth; (4) Incorporating the boundary conditions of the rock during testing, a mechanical model of rock fracture induced by ultrasonic high-frequency vibration, taking into account the effects of static load, is established. The model highlights a significant spatial disparity in the displacement of particles within the rock, with a greater reduction in the maximum displacement amplitude as the distance from the excitation surface increases. As the layer height varies from \(h\) to \(3/4\)\(h\), \(h/2\), and \(h/4\), the displacement amplitudes of rock particles in the corresponding horizons decrease by 0.076, 0.293, and 0.617, respectively.  
All the authors contributed to publishing this paper. [PERSON] and [PERSON] conceived and designed the research. [PERSON] performed the experiments and wrote the original manuscript. [PERSON] and [PERSON] participated in the data analysis and manuscript modification. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China, (52374146, 51874282), and the Six Talent Peaks Project in Jiangsu Province (GDZB-052).  
Not applicable.  
Data Availability StatementData is contained within the article.  
Great appreciation goes to the editorial board and the reviewers of this paper.  
The authors declare no conflict of interest.