Tunnel Waterproofing

Tunnel sealing systems are constructed underground on the job site. To protect against the ingress of moisture, a plastic sealing system made of HDPE, PP, PVC or TPO is normally used after completion of the concrete coating.

Tunnelling, as part of civil engineering, includes the construction of all underground cavities such as tunnels, galleries, shafts or caverns. Tunnel waterproofing systems are constructed in open-cast or underground mining and are sealed with geomembranes to prevent water from entering after the concrete lining has been completed. With the right welding method, the right automatic welding machines and manual hot air tools from Leister, every tunnel construction project can be brought to a successful conclusion.

Overhead welding

Geomembranes made of HDPE, PP, PVC or TPO are processed at right angles to the tunnel route using the overlap welding method. Due to the shape of the tunnel, it is inevitable to work with the welding machine above the head. This is required in effort to cover the tunnel ceiling in the upper third of the tunnel cross-section, also known as the calotte, with Geomembranes.

Welding the geomembrane lining and the side walls in tunnels (sometimes referred to as elm trees) is no less strenuous. Using a hot air hand tool or automatic welder in the required position for several hours requires stamina and strength. In addition, a correspondingly light and ergonomic tool is needed to generate high-quality welding seams on a consistent basis. Light and flexible automatic welding machines are required for "overhead welding." With TWINNY S, TWINNY T, COMET and UNIDRIVE 500, Leister offers several suitable machines that are ideal for waterproofing membranes in tunnels.

Tightly welded connections


In tunnel construction, not everything can be sealed with the GEO automatic welding machines from Leister. For welding connections and similar work, hand extruders are used to seal seams with welding rod. Handy heat guns are used for detail work since automatic welders are too large.

Check tunnel seams


Test needles, punching devices for test samples and test bells are particularly important in tunnel construction. It is essential to avoid structural defects and damaged areas such as holes and cracks in the material. Therefore, it’s important to pay special attention to the accessories needed for quality testing in tunnels. Leister is an excellent provider of the appropriate testing equipment needed for testing the weld seams and making work easier.