# Impact Analysis and Optimization of Key Material Parameters of Embedded Water-Stop in Tunnels
## 1 Introduction  
During tunnel construction, seepage water can not only delay construction progress but also cause serious accidents such as tunnel collapse [1], bringing great difficulties and safety hazards to the construction. In addition, seepage water adversely affects the safety and durability of tunnel lining [2], as well as the service life of tunnel facilities [3, 4]. At the same time, seepage water can also deteriorate the environment inside the tunnel and seriously affect traffic [5], making it one of the main factors causing problems during tunnel operation [6, 7]. Therefore, waterproofing is crucial to tunnel engineering, and lining joints are an important cause of water leakage. To prevent leaks at the joint, water-stops are generally installed in engineering projects to block water [8]. A water-stop is a strip made and installed to prevent water infiltration. It utilizes the high elasticity and compressive deformation of rubber to generate elastic deformation under various loads, thereby tightening and sealing, effectively preventing water leakage and seepage of building components.  
Currently, there is no clear regulation in China regarding the selection of waterproofing measures for highway tunnel joints, while the joint waterproofing measures for railway tunnels include embedded water-stops, back-adhesive water-stops, waterproof sealingmaterials, etc. Generally, the selection should be based on the waterproofing grade. When the waterproofing grade is higher than level three, a combination of multiple waterproofing measures should be used, among which the embedded water-stop is a mandatory measure [9].  
Since the successful development of rubber water-stops [10], polymer material water-stops have become the mainstream of water-stops. Rubber and plastic are the main materials of water-stops, with rubber being the primary one. There are many types of composite material water-stops, including steel-edged rubber water-stops compounded with rubber and metal, rubber water-stops embedded with metal mesh, and other [11] compounded water-stops. Therefore, the existing water-stop materials are mainly rubber-based and diverse and have become relatively mature after a long period of development.  
However, in practical engineering, the expected waterproofing effect of water-stops is often difficult to achieve [12]. [PERSON] et al. [13] indicate that the poor adhesion between rubber and concrete results in the waterproofing effect of water-stops, which is mainly generated from two aspects: one is enhancing the seepage resistance, and the other is prolonging the seepage path. [PERSON] et al. [14] have proposed that construction difficulties are the main reasons for the poor quality of tunnel joint waterproofing, including the low stiffness of rubber water-stops and the complexity of installation techniques. To address this issue, they proposed a new type of embedded water-stop with higher stiffness and transverse internal reinforcement. [PERSON], [PERSON], and [PERSON] et al. [15; 16; 17; 18] believe that improving the adhesion between water-stops and concrete can effectively improve their waterproof performance.  
In this paper, the commonly used embedded water-stop in engineering is taken as the research object. The mechanism of the water-stop is introduced, and the influence of the material hardness and the adhesion between the water-stop and concrete on its deformation stress state are analyzed through finite element simulation. Furthermore, an optimization experiment on the bond strength between the water-stop and concrete is conducted.