## 3 Results and Discussion
### Mechanical Properties
#### 3.3.1 Stress-Strain Curve
This effect arises because confining pressure facilitates the closure of internal cracks within the sample, thereby enhancing its plastic deformation capacity. Figure 18 presents the stress-strain curves of the grouting reinforcement body with a 30\({}^{\circ}\) crack dip angle subjected to various freeze-thaw cycles under confining pressures of 3 MPa and 9 MPa. The stress-strain curves of grouting reinforcement bodies with 30\({}^{\circ}\) and 0\({}^{\circ}\) crack dip angles exhibit no significant differences from the compaction stage through the elastic and unstable extension stages. However, noticeable differences arise in the post-peak strength region. In Figure 18a, multiple peaks are observed following the peak strength in the stress-strain curve of the grouting reinforcement body subjected to 0 freeze-thaw cycles. This phenomenon is attributed to the confining pressure restricting slippage along the fracture surface, allowing the sample to continue bearing a portion of the axial stress. In the same figure, the stress-strain curve of the grouting reinforcement body after undergoing freeze-thaw cycles is similar to that of the sample with a 0\({}^{\circ}\) crack dip angle under a 3 MPa confining pressure. After reaching peak strength, the axial stress decreases rapidly, leading to brittle fracture. This behavior is attributed to the weakening effect of freeze-thaw cycles on the confining pressure, which alters the internal pore structure of the rock and diminishes the cohesive forces between internal particles. The stress-strain  
Figure 17: Stress–strain curves of sample (0\({}^{\circ}\)) (a) \(\sigma\)3 = 3 MPa; (b) \(\sigma\)3 = 9 MPa. curves in Figure 18b show significant differences compared to those in Figure 18a. Notably, after reaching peak strength, the stress does not sharply decline, and the sample does not experience immediate brittle failure. This behavior is observed because these samples are subjected to triaxial compression under a high confining pressure of 9 MPa, where the weakening effect of freeze-thaw cycles on the confining pressure is not as pronounced. Figure 19 presents the stress-strain relationship curves for the grouting reinforcement body with a 45\({}^{\circ}\) crack dip angle, subjected to varying confining pressures and freeze-thaw cycles. As depicted in Figure 19a, under a confining pressure of 3 MPa, the stress-strain curve of the grouting reinforcement body reaches peak strength shortly after the elastic deformation phase, following a brief compaction stage. As axial strain increases, the axial stress rapidly decreases, leading to the brittle failure of the grouting reinforcement body. This behavior is attributed to the initial load being borne by both the grouting reinforcement body and the slurry-rock interface layer during axial loading. When the stress increases and reaches the shear strength of the slurry-rock interface layer, the rock block begins to slip along the fracture surface. Due to the low confining pressure, the restriction on rock block slippage is minimal, preventing the slip from being adequately controlled, which results in the observed curve. As illustrated in Figure 19b, under a confining pressure of 9 MPa, the stress-strain curve of the grouting reinforcement body exhibits two distinct peaks. After each peak, the stress slightly decreases before gradually increasing with strain, demonstrating a trend of strain hardening. The first peak signifies the moment when the grouting reinforcement body reaches its compressive strength. However, due to the restraining effect of the confining pressure, slippage along the fracture surface is prevented, allowing the rock to continue  
Figure 19: Stress–strain curves of sample (45\({}^{\circ}\)) (a) \(\sigma\)3 = 3 MPa; (b) \(\sigma\)3 = 9 MPa. Figure 18: Stress–strain curves of sample (30\({}^{\circ}\)) (a) \(\sigma\)3 = 3 MPa; (b) \(\sigma\)3 = 9 MPa. bearing the axial stress, which leads to the formation of a second peak.