Underground structures are subject to deterioration conditions in which water leakage occurs through cracks due to the long-term influence of soil and groundwater. Therefore, composite waterproofing sheets can play an important role in securing the leakage stability of structures by combining them with concrete structures. In this study, a total of eight composite waterproofing sheets were used according to the thickness of the compound and the properties of the material attached to the concrete, and the deformation characteristics at the bonding surface were identified through repeated tensile tests. Types A, B, and C, with a compound thickness of 1.35 to 1.85 mm and a single layer, had strong bonding performance, with a deformation rate of 0.5 to 2 x 10-4 and a DE/RE ratio of 0.3 to 1.3; tensile deformation progressed while maintaining integrity with the concrete at the bonding surface. Types D and E were viscoelastic and non-hardening compounds with a compound thickness of 1.35 to 3.5 mm, where the strain rate due to tensile deformation was the lowest, at 0.1 x 10-4 or less, and the DE/RE ratio was -5 to 3; therefore, when internal stress occurs, the high-viscosity compound absorbs it, and the material is judged to have low deformation characteristics. Types F, G, and H, which were 2 to 2.9 mm thick and had two layers using a core material, were found to have characteristics corresponding to tensile deformation, as the strain rate increased continuously from 0.2 to 0.5 x 10-4, and the DE/RE ratio increased up to 8 mm of tensile deformation.

A survey and assessment of the technical condition of basement and semi-basement structures in public buildings aged 60 to 130 years were conducted to evaluate their suitability for use as basic shelters. Based on the survey results, the most adverse impacts were identified, including changes in groundwater levels, improper building operation, and the characteristic damages to underground structural elements. Structural solutions were proposed to eliminate the consequences of these damages. The reviewed cases indicate that the vertical and horizontal waterproofing systems used during construction cannot perform their function throughout the building's entire life cycle. When designing new buildings, waterproof materials should be used for the enclosing structures of underground premises. While this may have a higher initial cost than membrane or coating waterproofing, considering life-cycle costs, it can provide a positive economic effect and improve the quality and comfort of the indoor environment.

When subjected to external loads from the ground and nearby construction, tunnel segmental lining joints are prone to damaging deformation. This can result in water leakage into tunnels, posing great safety risks. With this issue in mind, we conducted a series of full-scale tests to study the effects of external loads on the waterproofing performance of longitudinal joints. A customized rig for testing segmental joints was developed to assess the effect of loading magnitude, eccentricity, and loading-unloading-reloading cycles on waterproofing performance. Additionally, the relationship between joint force, sealing gasket deformation, and waterproofing pressure was investigated. The results indicate that: (1) the sealing gasket's compression rapidly decreases as external loads increase, which weakens the waterproofing capacity of the joint; (2) the watertightness limit dramatically decreases as the bending moment increases; (3) a loading-unloading-reloading cycle leads to degradation of the joint' s waterproofing performance. The findings of this study provide a reference for subsequent waterproofing design of segmental tunnel joints, helping ensure the safety of tunnels throughout their operational lifespans.