## 3 Results and Discussion
### Mechanical Properties  
#### 3.3.1 Stress-Strain Curve  
Following water saturation and freeze-thaw cycles, grouting reinforcement bodies with varying crack dip angles were subjected to uniaxial and triaxial compression testing. The analysis of the experimental data revealed a significant influence of crack dip angle, confining pressure, and freeze-thaw cycles on the stress-strain behavior of the grouting reinforcement body. To explore the effect of these factors, the stress-strain relationship curves for grouting reinforcement bodies with different crack dip angles were analyzed under confining pressures of 3 MPa and 9 MPa. As shown in Figure 17, when the crack dip angle is 0\({}^{\circ}\) and the confining pressure is set at 3 MPa and 9 MPa, the stress-strain curve of the grouting reinforcement body closely resembles that of intact red sandstone. The primary deformation characteristics of the grouting reinforcement body, under varying confining pressure conditions, can be divided into five distinct stages: (1) Compaction stage: In the initial loading stage, the axial stress-strain curve of the grouting reinforcement body exhibits a mildly concave trend. As the axial stress gradually increases, the original micropores and cracks within the sample progressively close, leading to compaction. This follows a nonlinear concave pattern, while the radial strain remains minimal, with overall behavior dominated by compressive deformation; (2) Transition from elastic deformation to stable propagation of micro-elastic cracks: This stage is visible in the curve, where the axial stress-strain relationship follows an approximately linear trajectory; (3) stable propagation of micro-elastic cracks: The curve deviates from the previous linear path, showing slight nonlinear deformation. Micro-cracks begin to form within the grouting reinforcement body, marking the onset of irreversible deformation; (4) unstable fracture propagation: As axial stress intensifies, micro-cracks propagate and accumulate, causing the grouting reinforcement body to transition from elasticity to plasticity. The accumulation of micro-cracks at various locations leads to peak strength and eventual catastrophic failure. During this stage, radial strain increases rapidly, with the grouting reinforcement body displaying pronounced shear dilation behavior;  
Figure 16: Evolution law of pore diameter of grouting reinforcement body. (5) post-peak fracture stage: After reaching peak strength, the internal structure of the grouting reinforcement body is compromised, and fracture behavior extends beyond microcrack expansion. With continued axial pressure, cracks within the sample propagate rapidly, forming an interconnected macroscopic fracture surface. The deformation of the sample is characterized by sliding along this macroscopic fracture surface, resulting in a rapid decline in load-bearing capacity, a sharp drop in axial stress, and the occurrence of a significant brittle fracture, accompanied by an audible cracking sound. The failure characteristics of the grouting reinforcement body under varying freeze-thaw cycles during the triaxial compression test were analyzed. As shown in Figure 17, with an increase in freeze-thaw cycles, the concavity of the compaction stage curve slightly increases, and the duration of the compaction stage is extended. The slope of the nearly linear stress-strain curve in the elastic deformation phase decreases, and the phase gradually shortens. The peak strength of the sample decreases, the brittle characteristics weaken, and the plastic characteristics enhance. Figure 17a,b demonstrate that confining pressure has a pronounced effect on the stress-strain curve of the grouting reinforcement body. As confining pressure increases, both the peak stress of the grouted reinforcement and the slope of the elastic deformation stage curve rise notably. Additionally, with increasing confining pressure, the strain at failure for the grouted reinforcement exhibits a substantial increase.