## 3 Results and Discussion  
### Mass and Wave Velocity Damage Analysis  
Table 4 shows the mass and wave velocity loss results calculated using Equations (2) and (3). Figure 10 shows the trend change in mass versus wave velocity damage after processing the data from Table 4. Three sandstone specimens were set up for each group of freeze-thaw temperatures. The specimens were numbered F-T-X-Y, where X denotes the  
Figure 8: Schematic diagram of particle changes. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Particle Type**} & \multicolumn{3}{c}{**Parameters**} \\ \cline{2-3}  & **Coefficient of Linear Expansion** & **Thermal Resistance** & **Specific Heat Capacity** \\  & \(\alpha\)**/(1\({}^{\circ}\)C\({}^{-1}\))** & \(\eta\)**/(\({}^{\circ}\)C\(\cdot\)W\({}^{-1}\).m\({}^{-1}\))** & \(\mathbf{C_{\
u}}\)**/(J\(\cdot\)kg\({}^{-1}\).\({}^{\circ}\)C\({}^{-1}\))** \\ \hline Rock particle & 0.053 & 2.59 & 878 \\ Water particle & 2.080 & 1.00 & 4216 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Freeze–thaw parameters. Figure 9: Heat transfer process diagram. number of freeze-thaw cycles, and Y represents the serial number of sandstones under the same grouping. According to Figure 10, with the increase in freeze-thaw cycles, the Mass Damage Factor (D\({}_{\text{m}}\)) generally shows an increasing trend, but the growth rate is different at different stages. Specifically, when the number of freeze-thaw cycles is lower than 60, the Mass Damage Factor's growth is gentler. The Mass Damage Factor increased from 0.28% to 0.30% during the phase of 20 to 40 freeze-thaw cycles and reached 0.43% during the period of 40 to 60 cycles. However, when the freeze-thaw cycles exceeded 60, the Mass Damage Factor jumped to 0.75%. This phenomenon suggests that 60 freeze-thaw cycles is a threshold value below which the sandstone mass loss is relatively small. While once exceeded, the sandstone mass damage increases rapidly. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Specimen** & **Pre-Freeze–** & **Post-Freeze–** & **Mass Loss/\%** & **Pre-Freeze-** & **Post-Freeze-** & **Wave Speed** \\
**Number** & **Thaw Mass/g** & **Thaw Mass/g** & **Mass Loss/\%** & **Speed/m-s\({}^{\text{-1}}\)** & **Speed/m-s\({}^{\text{-1}}\)** & **Speed/m-s\({}^{\text{-1}}\)** \\ \hline F-T-20-1 & 589.56 & 587.86 & 0.288 & 3225.66 & 3212.76 & 0.4 \\ F-T-20-2 & 594.20 & 592.52 & 0.283 & 3456.98 & 3446.61 & 0.3 \\ F-T-20-3 & 591.89 & 590.29 & 0.270 & 3015.28 & 2994.17 & 0.7 \\ Average value & 591.88 & 590.22 & 0.280 & 3232.64 & 3217.85 & 0.5 \\ F-T-40-1 & 595.66 & 593.66 & 0.336 & 3456.78 & 3415.30 & 1.2 \\ F-T-40-2 & 588.98 & 587.18 & 0.306 & 3598.58 & 3537.40 & 1.7 \\ F-T-40-3 & 590.27 & 588.57 & 0.288 & 3569.28 & 3515.74 & 1.5 \\ Average value & 591.60 & 589.80 & 0.310 & 3541.55 & 3489.48 & 1.5 \\ F-T-60-1 & 589.75 & 587.15 & 0.441 & 3426.20 & 3350.82 & 2.2 \\ F-T-60-2 & 590.70 & 588.3 & 0.406 & 3265.10 & 3173.68 & 2.8 \\ F-T-60-3 & 592.30 & 589.6 & 0.456 & 3356.12 & 3295.71 & 1.8 \\ Average value & 590.92 & 588.35 & 0.434 & 3349.14 & 3273.40 & 2.3 \\ F-T-80-1 & 590.22 & 586.02 & 0.712 & 3567.55 & 3446.25 & 3.4 \\ F-T-80-2 & 591.26 & 586.76 & 0.761 & 3055.12 & 2966.52 & 2.9 \\ F-T-80-3 & 595.10 & 590.40 & 0.790 & 3099.70 & 3000.51 & 3.2 \\ Average value & 592.19 & 587.73 & 0.754 & 3240.79 & 3137.76 & 3.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of damage before and after freeze–thaw. Figure 10: Mass and wave velocity damage. The water-ice phase change in sandstone causes dislocations and displacements of the internal mineral particles, particle shedding on the surface, and rock debris falling, resulting in a loss of sandstone mass. As the freeze-thaw cycles increase, the displacement of the sandstone's internal mineral grains accumulates, leading to a rapid increase in the Mass Damage Factor at a certain point in time. The wave velocity magnitude reflects the degree of development of defects within the sandstone.