## 3 Analysis of Test Results
### Rock Mechanical Properties Under the Interaction of Multiple Factors
#### 3.3.2 Factor Interactions on Peak Stresses  
Figures 8-10 show that under the combined effects of grouting material and roughness, grouting material and confining pressure, and fracture dip angle and roughness, the peak stress of the rock specimen increases. This increase is greater than the effect of the independent combination of the two factors: the increase in peak stress due to the interaction of grouting material and roughness is 7.68%, due to the interaction of grouting material and confining pressure is 17.42%, and due to the interaction of fracture dip angle and roughness is 19.69%. From the density of the contour lines, it is evident that confining pressure in the interaction between grouting material and confining pressure, fracture dip angle in the interaction between fracture dip angle and roughness, and grouting material in the interaction between grouting material and roughness have a more prominent influence on peak stress, respectively. Interaction between grouting material and roughness: As the strength and roughness of the grouting material increase, the peak stress shows a clear increasing trend, and the interaction between the two further strengthens this effect. Specifically, when the strength and roughness of the grouting material are both at a high level, the increase in peak stress is the greatest; when they are at a medium or low level, the increase in peak stress tends to stabilize. Specifically, during the transition from low to high grout material strength, the peak stress gain increased nonlinearly from 5.96 MPa to 11.06 MPa, an increase of 1.86-times, as the roughness increased. Under the condition of low-strength grouting material, although the increase in roughness will enhance the frictional resistance and bite effect of the fracture surface, the reinforcement effect of the low-strength groutingmaterial itself is limited, resulting in a small increase in peak stress. Under the condition of high-strength grouting material, the material forms a stronger anchoring system with the rough fracture surface, which not only effectively disperses the external stress but also further reduces the stress concentration effect at the fracture tip, thus significantly increasing the peak stress. In addition, during the transition from low to high roughness, as the strength of the grouting material increases, the peak stress gain increases nonlinearly from 27.76 MPa to 32.86 MPa, an increase of 1.18-times. Under low roughness conditions, the fracture surface is relatively smooth, and the bite with the grouting material is weak, so even if the strength of the grouting material increases, its effect on increasing the peak stress is relatively limited. Under high roughness conditions, the uneven structure of the fracture surface can significantly enhance the anchoring effect of the grouting material, so that the high-strength characteristics of the grouting material can be brought into full play, resulting in a greater increase in peak stress. Interaction between grouting material and confining pressure: As the strength of the grouting material and confining pressure increase, the overall trend of peak stress variation is similar to the interaction between grouting material and roughness, exhibiting a strong synergistic effect. During the transition from low to high confining pressure, as the strength of the grouting material increases, the gain in peak stress increases nonlinearly from 27.76 MPa to 43.83 MPa, an increase of 1.58-times. Under low confin  
Figure 8: Visualization of the interaction effect between grouting material and roughness on peak stress. Figure 9: Visualization of the interaction effect between grouting material and confining pressure on peak stress. the confining pressure has a weak inhibitory effect on crack propagation, and the increase in the strength of the grouting material only has a limited strengthening effect in the grouting crack area.