Tunnels consisting of tubing elements which are built with a tunneling shield or Tunnel Boring Machine (TBM) represent the most advanced method used in tunnel construction. However, despite heavy reinforcement, cracks can appear on the concrete surface due to high pressure from hydraulic stresses on the tubbing elements. In order to prevent moisture damage due to water penetration and subsequent corrosion of the reinforcement, these cracks are sealed with standardized injection methods. Since the cracks can be assumed to be static, crack-bridging as well as structural rebonding products are suitable.
Another common problem in tunnel construction is the partial failure of the outer seal and consequent leakage through the tubing element joints. Very often curtain injection behind the tubing element is the chosen method of repair. A grid of drill holes are drilled through the tubbing element and are injected with an injection gel. The injection material solidifies the adjacent layers of earth and waterproofs the building component from the backside.