Underwater tunnels such as immersed tunnels and immersed floating tunnels have shown rapid development in recent years. In the construction of underwater tunnels, new materials with high performance and new technologies such as machine learning are required due to the large water loading and other challenges. Compared to tunnels constructed using tunnel boring machines (TBMs) and the drill-and-blast method, underwater tunnels are not widely constructed in tunnel engineering due to high construction difficulties, especially with immersed floating tunnels. Thus, limited research has been conducted in the area of underwater tunnels. Furthermore, current underwater tunnel research focuses on the construction process, conventional simulations, and model tests. As a result, further investigation is required to address the issues regarding new materials and technologies to improve the construction of underwater tunnels.

This Special Issue aims to publicize conjectural and procedural developments, and significant technical applications of new materials in underwater tunnels such as high water-tightness materials, concrete with toughness, joint water-stop rubber, etc., corresponding application and simulation technologies. This Special Issue invites original research and review articles on the application and simulation of new materials for underwater tunnels.

Potential topics include but are not limited to the following:

• Empirical or theoretical models for predicting the performance of high water-tightness materials
• Laboratory test methods corresponding to concrete with toughness
• Long-term behavior of joint water-stop rubber
• Theoretical models of water-stop rubber
• Laboratory test methods corresponding to water-stop rubber
• Reliability of underwater tunnels under large water loading
• Performance of underwater tunnels using new materials
• Long-term behavior of concrete undersea
• Numerical simulation or model tests on underwater tunnels
• Evaluation of service status of underwater tunnels
• Use of machine learning technology for underwater tunnels