# Impact Analysis and Optimization of Key Material Parameters of Embedded Water-Stop in Tunnels
## 4 Conclusions  
Based on the waterproof working mechanism of embedded water-stops, this chapter establishes finite element models of water-stops with different material parameters from the perspectives of water-stop hardness and the bonding force between water-stops and concrete lining. The effects of key material parameters on the stress and deformation of water-stops are analyzed, revealing the laws of the influence of water-stop hardness and the bonding force between water-stops and concrete lining on the stress and deformation of water-stops and their waterproof capacity. An optimization method for the bonding force between water-stops and concrete lining is proposed and verified through experiments. The main conclusions are as follows:  
1. Water-stop hardness is a comprehensive indicator of its mechanical properties, such as elasticity, plasticity, strength, and toughness. The stress deformation of the water-stop will increase with the increase in hardness. Reducing the hardness of the water-stop can optimize its stress deformation state. However, when the hardness of the water-stop is low, the risk of tearing and puncturing increases, the construction difficulty may also increase, and the engineering quality may decrease. The hardness of water-stops specified in the code is 55-65, so it is recommended that the hardness of water-stops be 55-60.
2. In addition to compression deformation, when the bonding force reaches a certain value, the bonding failure area between the water-stop and the lining concrete will decrease with the increase in the bonding force. The stress deformation of the water-stop will increase with the increase in the bonding force. When the bonding force is large, the stress deformation of the water-stop will exceed the dangerous stress value. This indicates that increasing the bonding force between the water-stop and the concrete can not only improve the water seepage resistance of the water-stop but also improve the waterproof reliability of the water-stop. However, to prevent excessive deformation stress, it is necessary to optimize the geometric structure of the water-stop simultaneously.
3. It is proposed to increase the bonding force between the water-stop and the concrete by applying an epoxy-quartz sand coating on the surface of the water-stop, and the coating with different epoxy thicknesses and quartz sand particle sizes is verified through experiments. The results show that this method can indeed increase the bond  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Working Condition** & **Test 1/MPa** & **Test 2/MPa** & **Test 3/MPa** & **Shear Bond Strength/MPa** \\ \hline
1 & / & 0.397 & 0.412 & 0.405 \\
2 & 0.306 & 0.376 & 0.344 & 0.342 \\
3 & 0.303 & 0.276 & 0.240 & 0.273 \\
4 & 0.202 & 0.223 & 0.246 & 0.224 \\
5 & 0.404 & 0.387 & 0.412 & 0.401 \\
6 & 0.432 & 0.423 & / & 0.428 \\
7 & / & 0.340 & 0.356 & 0.348 \\
8 & 0.215 & 0.248 & 0.256 & 0.240 \\
9 & 0.372 & 0.394 & 0.356 & 0.374 \\
10 & 0.328 & 0.332 & 0.312 & 0.324 \\
11 & 0.237 & 0.262 & 0.228 & 0.243 \\
12 & 0.224 & 0.206 & 0.252 & 0.227 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Shear bond strength of cement-rubber coated specimens.  
ing force between the water-stop and the concrete. When the epoxy layer thickness is 2 mm, and the quartz sand particle size is 26-40 mesh, the effect is the best.  
Conceptualization, Y.W.; methodology, L.W.; validation, L.W.; investigation, C.G.; resources, C.G.; data curation, L.W.; writing--original draft preparation, L.W.; writing--review and editing, C.G.; visualization, C.F.; project administration, Y.W. and C.F. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Department of Transport of Hubei Province Science and Technology Project: 2020-186-2-5.  
Not applicable.  
All data are available from the author.  
The authors declare no conflict of interest.