# Impact Analysis and Optimization of Key Material Parameters of Embedded Water-Stop in Tunnels
## 2 Optimization of Key Parameters for Water-Stop Materials
### Analysis of the Influence of Water-Stop Hardness on Its Deformation Force State
Therefore, it can be considered that a lower material hardness of the water-stop has a certain effect on improving the deformation stress of the water-stop. In conclusion, although reducing the hardness of the water-stop can improve its stress deformation state, the hardness of the water-stop is a comprehensive indicator of its mechanical properties and the ability to resist hard objects pressing into its surface. If the hardness of the water-stop is too low, it may cause damage to the water-stop during construction or service, and the risk of the water-stop being torn or punctured is higher. Secondly, when the hardness of the water-stop is low, i.e., softer, it may cause difficulties in installation and positioning during construction, increasing the construction difficulty and reducing the project quality. The hardness range of the water-stop specified in the code is 55-65; based on this, it is recommended that the hardness of the water-stop in the design should be 55-60. Analysis of the Influence of the Bonding Property of Water-Stops on Their Deformation and Stress State  
The waterproofing ability of water-stops depends on their surface contact pressure and bonding force. The contact pressure is difficult to change due to the structure; the waterproofing ability could be improved by increasing the bonding force of water-stops. To analyze the deformation and stress state of water-stops under different bonding forces, the bonding forces between rubber and concrete obtained from the tests are used as the basis, and different bonding forces are set, as shown in Table 2. A finite element model is established using ABAQUS/Standard, and the deformation is applied in the same way as described above. The calculation results of the water-stop deformation stress are shown in Figures 8-10. The results show that: 1 During tensile deformation, the deformation stress of the water-stop exhibits significant fluctuations after working condition 6, with the deformation stress first increasing and then decreasing. Before working condition 7, the deformation stress eventually tends to approximate values, while the deformation stress in working condition 8 shows a significant increase; 2 During compression deformation, the deformation stress curves of each working condition are almost identical, indicating that the compression deformation is mainly due to the concrete lining squeezing the pores of the water-stop, which hardly destroys the bond between the water-stop and the concrete. The size of the bond strength between the water-stop and the concrete has little effect on the compression deformation stress of the water-stop; 3 During settlement deformation, the deformation stress of the water-stop does not show an obvious regularity with the change in bond strength before working condition 6, while after working condition 6, a clear regularity is observed, with the deformation stress increasing with the increase in bond strength. \begin{table}
\begin{tabular}{c c c} \hline
**Working Condition** & **Normal Adhesive Force/MPa** & **Tangential Adhesion Force/MPa** \\ \hline
1 & 0.000 & 0.000 \\
2 & 0.193 & 0.076 \\
3 & 0.386 & 0.151 \\
4 & 0.579 & 0.227 \\
5 & 0.772 & 0.302 \\
6 & 1.158 & 0.453 \\
7 & 1.930 & 0.755 \\
8 & 3.088 & 1.208 \\ \hline \end{tabular}
\end{table} 
Table 2: Rubber and concrete bonding force parameters. stop and the concrete lining. In Figure 11, the schematic diagrams of the bond failure area after the tensile deformation of the water-stops from Case 4 to Case 8 are shown. It can be seen from the figure that in Case 4 and Case 5, the bond failure area after deformation just covers the first water-stop rib on both sides (the bond failure area of the cases before Case 4 is similar). In Case 6 and Case 7, after the water-stop deformation, the bond failure area is between the first water-stop ribs on both sides, just at the edge of the water-stop ribs. After the deformation of Case 8, the bond failure area has the smallest range, and the water-stop ribs are not within the failure range.