A Study on the Effectiveness of Surface Protection Methods for Underground Tunnel Structures in Singapore

Underground structures are required in densely populated urban areas where space is limited. Singapore is a country with sparse land space and has several underground structures such as roads tunnels, rail tunnels (mass rapid transit), and common utility services tunnels. Some of these structures were built more than 40 years ago and are prone to structural damage due to water seepage and material degradation. Defects such as leaks, cracks, and spalling concrete due to corrosion damage were commonly found in these underground structures. In this paper, various aspects affecting the durability of underground structures are presented. A study has been carried out to identify major factors contributing to the underground structure damages and to enhance the durability of these structures, as part of this study, three different surface protection methods, namely, impregnation, hydrophobic impregnation, and coating methods have been explored. This paper summarizes the details of surface protection methods and tests carried out to evaluate the effectiveness of surface protection methods to enhance the durability of underground tunnel structures.