## 3 Analysis of Test Results
### Mechanical Properties of Sandstone Under the Action of a Single Factor
During the steady growth phase (section ab), acoustic emission events are relatively few, and the cumulative ringing count increases gradually, corresponding to sections I and II of the stress-strain curve. This phase reflects the closure and initial expansion of microcracks in the rock specimen. After point b (the sudden increase point), acoustic emission activity rises sharply, and the cumulative ringing count increases rapidly, marking the start of the sudden increase phase. This phase corresponds to stages III and IV of the stress-strain curve, representing crack expansion and macroscopic penetration, leading to rock failure. Figure 7a illustrates the effect of freeze-thaw cycles on the ringing count. As the number of freeze-thaw cycles increases, the number of steady-state acoustic emission events rises, the characteristic frequency of microcracks becomes evident, and the sudden increase point shifts earlier (by 34.73% for 40 freeze-thaw cycles compared to the unfrozen rock specimen). Additionally, rupture activity occurs earlier, the sudden increase period is prolonged, and the time for microcrack expansion into macroracks increases. Both the peak ringing count and the cumulative ringing count increase, while the energy released during rock failure also rises. In the initial compaction stage, the ringing count temporarily increases with the number of freeze-thaw cycles. After 40 freeze-thaw cycles, the initial cumulative ringing count of the rock specimen is 1.52-times that of the unfrozen sample, indicating that freeze-thaw cycles increase the number of micropores and microcracks within the rock. Under compression, internal micropores gradually connect, leading to the formation of more cracks. During the plastic deformation stage, the frequency of sudden increases in the ringing count rises significantly, and the slope of the cumulative \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Factor** & **Effect on Strength** & **Effect on Stiffness** & **Influence Mechanism** \\ \hline Freeze–thaw & Peak stress & Elastic modulus & Freeze–thaw cycles cause microcrack expansion and deterioration of pore structure, resulting in a gradual decrease in strength and stiffness, exhibiting typical cumulative damage effects. \\  Cycles & decreases by 55.37\% & Elastic modulus & Growing materials improve adhesion and support, extending residual strength, enhancing peak stress, and improving overall stiffness. \\  Cycles & decreases by 55.37\% & Elastic modulus & Roughness improves slurry anchoring, optimizes stress distribution, delays crack propagation, and enhances the rock’s stability, thereby improving mechanical properties. \\  Groups & Peak stress increases by 113.61\% & Elastic modulus & Growing materials improve adhesion and support, extending residual strength, enhancing peak stress, and improving overall stiffness. \\  Roughness (JRC) & Peak stress increases by 13.25\% & Elastic modulus & Roughness improves slurry anchoring, optimizes stress distribution, delays crack propagation, and enhances the rock’s stability, thereby improving mechanical properties. \\  Groups & Peak stress increases by 118.76\% & Elastic modulus & Fracture dip angle optimizes stress transfer, reduces slippage and cracking, increasing elastic modulus and peak stress, thereby enhancing stability. \\  Configning & Peak stress increases by 140.2\% & Elastic modulus & Confining pressure increases rock density, limits deformation, enhances stiffness and strength, and promotes the transition from brittle to ductile failure. \\  Pressure & Peak stress increases by 140.2\% & Elastic modulus & Confining pressure increases rock density, limits deformation, enhances stiffness and strength, and promotes the transition from brittle to ductile failure. \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Influence of factors on sandstone’s mechanical properties. ringing count curve increases, indicating that freeze-thaw cycles accelerate crack expansion and connection.