## 2 Materials and Methods
### Experimental Results and Analysis
In addition, in order to more accurately reveal the profound influence of moisture content changes on the mechanical properties of the core, this paper further studies the strain rate dynamics of the core under different moisture content conditions in the pressure-increasing and pressure-reducing cycle experiment and the entire research period. Relevant charts clearly show the evolution law and characteristics of the core strain rate under various moisture content environments. Figure 12 presents the complex relationship between the strain rate and moisture content of limestone cores in the water pressure test. Through the comparative analysis of the whole process, including pressurization and decompression states, it can be found that the strain rate change is closely related to the moisture content. Under the whole process and pressurization conditions, the strain rate gradually decreases with the increase in moisture content, and the two show a significant negative correlation linear relationship. The reason is that water fills the pores and micro-cracks of limestone, making the internal structure of the rock more compact. During the pressurization process, water exerts a lubricating effect and reduces the frictional resistance between particles, which makes the rock more prone to deformation when subjected to external pressure and finally leads to a decrease in strain rate. However, under decompression conditions, the strain rate gradually increases with the increase in moisture content, showing a positive correlation linear relationship. This is because during the decompression process, the water pressure in the pores is gradually released, and the supporting effect of water on rock particles is weakened. As the moisture content increases, the volume of water relatively increases. During decompression, it will cause a greater degree of pore pressure change, which makes rock particles more prone to relative displacement and rearrangement, thereby causing an increase in strain rate [30]. \begin{table}
\begin{tabular}{c c c c} \hline
**Moisture Content (\%)** & **Average Strain Mutation (\(10^{-6}\))** & **Average Strain Rate Amplitude (S\({}^{-1}\))** & **Elastic Modulus (GPa)** \\ \hline
0 & 6.79 & 2.08 & 29.44 \\
50 & 5.58 & 1.28 & 34.20 \\
80 & 5.26 & 0.48 & 38.04 \\
100 & 4.67 & 0.34 & 42.87 \\ \hline \end{tabular}
\end{table} 
Table 1: Influence of moisture content on rock deformation characteristics. Figure 12: Relationship between different moisture content of specimens and average strain rate amplitude under different loading states. (**a**) Variation in average strain rate amplitude of rocks with 100% moisture content under different loads. (**b**) Variation in average strain rate amplitude of rocks with 80% moisture content under different loads (**c**) Variation in average strain rate amplitude of rocks with 50% moisture content under different loads. (**d**) Variation in average strain rate amplitude of rocks with 0% moisture content under different loads. The specific reason for the deformation of limestone specimens is because the high-pressure water changed the pore structure of the rock; therefore, in this paper, the porosity, movable fluid saturation, and permeability of limestone specimens before and after the test were tested by nuclear magnetic resonance (NMR), and the exact pore sizes were obtained, which are defined as follows: microporous: less than 10 \(\upmu\)m, microporous: 10-20 \(\upmu\)m, small porous: 20-50 \(\upmu\)m, medium porous: 50-100 \(\upmu\)m, macropores: greater than 100 \(\upmu\)m [31].