Tunnel waterproofing is vital for ensuring the long-term safety and durability of underground structures, especially under complex stress and environmental conditions. This paper systematically reviews current waterproofing technologies, including sheet materials, spray-applied membranes, and grouting agents. It also introduces recent innovations such as double-bonded systems, energy-absorbing layers, and self-healing hydrogels. Despite the significant progress made in recent years in developing new waterproofing materials and structural systems, several key challenges remain in practical engineering applications. On one hand, the bonding compatibility between different material interfaces is still insufficient, making them prone to delamination or slippage under repeated loading or uneven stress. On the other hand, research on the adaptability and long-term service stability of materials under extreme environments, such as high temperature, high salinity, and freeze-thaw cycles, is still limited. In addition, there is a lack of standardized durability evaluation criteria and complete life-cycle performance testing systems. The article follows a logical structure from traditional materials to new systems, comparing their mechanical, waterproofing, environmental, and construction performances. This study points out the need for smart, flexible materials and integrated systems to support future green and deep-environment tunnel projects.
Ruolin Wang (Wed,) studied this question.