## 3 Results and Discussion
### Degradation of Mechanical Properties of the Specimen  
Table 1 displays the mechanical characteristics of the fissure-grouted rock specimens following dry and wet cycling. Figure 5 depicts the stress-strain curves of typical fissure-grouted rock specimens. As can be seen, each rock specimen's stress-strain curve displays a typical five-stage state. Pore-fracture-compacting stage (A section): At the beginning of stressing, the initially opened structural surface or microfractures inside the specimen gradually closes, and the specimen is compacted, resulting in an early nonlinear deformation and an up-concave stress-strain curve. Stage of elastic deformation (B section): Nearly straight stress-strain curve. The elastic modulus of the fissure-grouted rock specimens is inversely proportional to the number of  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**No. **} & **Number of** & **Peak Strength** & **Peak Strain** & **Modulus of Elasticity** \\  & **Cycles** & **(MPa)** & **(\%)** & **(GPa)** \\ \hline A–1 & 0 & 16.68 & 0.716 & 3.683 \\ A–2 & 0 & 21.68 & 0.685 & 4.581 \\ A–3 & 0 & 18.29 & 0.609 & 3.183 \\ A–4  
dry and wet cycles, as shown in the figure, where the slope of the straight line segment drops as the number of dry and wet cycles increases. Stage of stable crack formation (section C): Although fresh microfractures begin to form inside the specimen and the slope of the stress-strain curve starts to decline with increasing stress, the microfractures are regulated by the applied load and progress in a steady state. The crack begins to steadily grow at the C section stage. The specimen begins to exhibit the expansion phenomenon from the C section as a result of the volume strain curve departing from a straight line and the volume of the inelastic component of the specimen growing. Cracks in the non-stable development stage (D-segment): The stress-strain curve is upwardly convex, and the formation of microcracks inside the specimen changes qualitatively as they grow until the specimen is entirely destroyed. The radial and volumetric strain rates rise quickly as the specimen's volume changes from decreasing to grow. At this point, the stress is at its peak. Figure 6 shows the sample failure. After the specimen reaches its maximum strength, its internal structure is harmed. Fractures in the specimen develop quickly, cross each other, and come together to produce a macroscopic fracture surface, but the specimen essentially stays intact, which is the post-rupture phase (segment E). The bearing capacity of the specimen then rapidly decreases with the increasing strain but does not reach zero, suggesting that the specimen still has some bearing capacity after rupture. The specimen deformation is then mostly expressed as a block slide along the macroscopic fracture surface. Additionally, the fissure-grouted rock specimens showed a considerable drop in uniaxial compressive strength after performing dry and wet cycles after comparing the uniaxial compressive strength of each specimen. After the initial few dry and wet cycles, this difference in intensity was particularly noticeable. When compared with the elastic modulus of each specimen of fissure-grouted rock in Table 1, the elastic modulus of the specimen lowers when more dry and wet cycles are applied to the specimens. Moreover, the declining trend becomes flat as the number of dry and wet cycles rises, as shown in Figure 7. The elastic modulus of each fissure-grouted rock specimen was calculated using the experimental data from uniaxial compression experiments. The relationship between the elastic modulus \(E_{n}\) and the number of cycles \(n\) of the fissure-grouted rock specimens after water-rock action was then fitted and analyzed. The fitted relationship equation was derived as follows:  
\[E_{n}=2.14e^{-\frac{n}{n+2}}+2.39, \tag{7}\]  
Figure 5: Stress–strain curves of typical fracture–grouted rock specimens under different numbers of wetting–drying cycles. Figure 6: Failed specimens under different cycles. (**a**) 0 cycles.