## 2 Materials and Methods
### Experimental Results and Analysis  
In the complete pressurization-depressurization cyclic experiment, the relationship between the strain and stress of the limestone core is significantly affected by the water content. Specifically, with the increase in water content, the strain response of the core to stress shows a corresponding increasing trend, as in Figure 7, in the complete pressure-increasing and pressure-reducing cycle experiment, when observing different moisture contents (0%, 50%, 80%, and 100%), it can be seen that during the first application of pressure, the cores with moisture contents of 0%, 50%, and 80% start to absorb surrounding moisture on their surfaces. This is because in the uncompressed state, the tiny pores and fractures on the surface of the core are in a state where water can enter, and the surrounding moisture can enter them. As moisture enters, these tiny pores and fractures are filled, thereby causing the core volume to expand and leading to an increase in strain. From the microscopic mechanism level, the interaction between water molecules and the surface of rock particles increases the distance between rock particles, which in turn causes the overall volume to expand. As the pressure gradually increases, the strain tends to be stable. This is because under the action of pressure, the internal stress distribution of the core gradually changes. During this process, the rock particles begin to rearrange, and theinternal pore structure also undergoes a certain degree of adjustment. When the stress distribution reaches a new equilibrium state, the strain tends to be stable. When the moisture content reaches 100%, the core does not experience the process of water absorption and expansion during the first compression. Its strain directly changes with the change in stress. This is because in the case of 100% moisture content, the pores and fractures of the core have been fully filled with water. When under pressure, water can no longer enter the pores and fractures to cause volume expansion. Instead, directly through the incompressibility of water and its effect on rock particles, the strain changes correspondingly with the change in stress. From the perspective of mechanical principles, at this time, water in the core makes the response of strain to stress more direct. In order to gain a clearer insight into the influence of moisture content changes on the mechanical properties of the core, this paper deeply analyzes the performance of the elastic modulus of the core under different moisture content environments during the pressure-increasing and pressure-reducing cycle and the entire experiment process. As shown in detail in Figure 8, it shows the changes in the elastic modulus of cores in each moisture content state under different water pressure conditions. Figure 8 above shows in detail the evolution law of the elastic modulus of rock cores with different moisture contents under different loading states. The elastic modulus is a physical quantity that measures the stress-strain relationship of rock within the elastic range. It can directly reflect the ability of rock to resist deformation. That is, the higher the elastic modulus, the stronger the ability of rock to resist deformation [29]. It can be clearly observed from Figure 8 that with the change in water pressure load, the elastic modulus of rocks with different moisture contents shows a clear trend: when the water pressure gradually increases, the elastic modulus of the rock correspondingly increases; when the water pressure decreases, the elastic modulus also decreases. This change law reveals that there is a positive correlation between water pressure and rock elastic modulus. The main reason is that rock is a porous medium, and its internal water-bearing state will change its own mechanical properties. When the water pressure increases, the water pressure in the pores also increases, which makes the effective stress between rock particles increase.