Tunnel waterproofing describes the installation of a continuous geomembrane barrier between the excavated rock face and the inner concrete shell of a tunnel structure. Groundwater ingress, chemical aggression and long-term seepage water pressure threaten the structural integrity of the inner lining. Naue Carbofol® geomembranes and Secutex® protection geotextiles provide a certified, plasticiser-free waterproofing solution with a long design service life.
Carbofol® geomembrane systems are deployed wherever a watertight, long-life barrier is required between the surrounding ground and the structural concrete lining.
Continuous membrane system with a long design life on high-speed and heavy-rail routes
Certified waterproofing for motorway, road, and urban underground tunnels under high groundwater pressure
High-pressure waterproofing for power waterways and pressure shafts in the energy sector
Chemical-resistant barrier for aggressive groundwater in mining and underground extraction
Tunnel waterproofing is subject to extreme mechanical loads during installation. Shotcrete surfaces are irregular; sharp rock edges create a puncture risk. Carbofol® geomembranes are manufactured from plasticiser-free polyethylene (PE), combining high flexibility with excellent puncture resistance. Secutex® protection geotextiles are placed directly on each side of the membrane as a mechanical buffer layer.
Practical advantages:
In tunnelling, the waterproofing system must manage both seepage water drainage and hydraulic pressure containment. The system build-up depends on whether the tunnel is designed as a drained or undrained structure.
The choice of waterproofing system depends on ground conditions, water chemistry, tunnel geometry and service life requirements. The table below provides a criterion-based decision guide.
| Criterion | Condition | Carbofol® PE geomembrane | Bentofix® X GCL |
|---|---|---|---|
| Hydrostatic pressure | High (undrained tunnels) | Primary choice: high tensile strength, continuous welded seal, testable seams | Suitable for moderate pressures; PE coating required for high pressure |
| Chemical aggression | Aggressive groundwater | Excellent: PE is chemically inert across a wide range of media | Check bentonite compatibility; Bentofix® X2 types offer enhanced resistance |
| Ground movement | Dynamic loads, seismic zones | High flexibility; rondelles with predetermined breaking points absorb deformation | Less suited to high-deformation or seismic zones |
| Filtration requirement | Seepage/drainage zones | Secutex® geotextile layer provides separation and filtration | Bentofix® X2 BFG 5300 addresses seepage in lower-pressure sealing zones |
| Installation complexity | Complex cross-sections | Click system, injection connections, waterstops handle all details on site | Better suited to flat or near-flat surfaces; less suited to complex arch geometries |
| Certified installation | QA required | Naue is certified installer (full member of Arbeitskreis Tunnelabdichtung e.V.) | Project-specific certification for Bentofix® in tunnel applications |
Continuous, verified seal over the full structure
Carbofol® welds are tested seam by seam using dual-channel welding. The smooth surface reveals any installation damage immediately. Certified installation by Naue ensures every element is traceable and compliant with relevant standards.
Full-service delivery: material, installation and compliance
Naue provides project-specific material sizing, certified on-site installation, end-to-end logistics and full compliance documentation. Naue is able to handle import, tax administration and regulatory compliance directly through international and local presence.
Long design service life: chemically inert and stable
Carbofol® is manufactured from polyethylene (PE) without plasticisers and is chemically inert. It is highly resistant to degradation and does not leach plasticisers or heavy-metal additives into groundwater over the design service life of the structure.
Tunnel waterproofing describes the installation of a continuous geomembrane barrier between the shotcrete primary lining and the inner concrete shell. It is required in all tunnels where groundwater ingress would compromise structural integrity, serviceability or occupant safety. Both drained and undrained tunnel designs are covered by the Carbofol® system.
Carbofol® PE geomembrane is the primary choice for tunnels with high hydrostatic pressure, complex cross-sections, aggressive groundwater chemistry or long design service lives. Bentofix® X types are used in lower-pressure sealing zones and specific seepage containment applications. Naue provides project-specific sizing and system recommendations. Please get in touch via our contact form.
Tunnel waterproofing is subject to national standards (e.g., ÖNORM B 2203 for NATM tunnels) and product standards (e.g., EN 13491:2005+A1:2016 for tunnel geosynthetic barriers). The Arbeitskreis Tunnelabdichtung e. V. defines quality control procedures for certified specialist companies. Naue is a full member and certified to its requirements.
A continuous, welded Carbofol® membrane with certified installation eliminates the risk of localised leakage and the costly remediation that follows. Project-specific material sizing minimises waste. For the Drammen Tunnel (170,000 m² installed, August 2021 to August 2022), Naue delivered a full-service solution including compliance, reducing the client coordination burden significantly.
Secutex® protection geotextile is fixed to the shotcrete surface first. Carbofol® membrane panels are fixed to the Secutex® layer using rondelles nailed to the shotcrete; the membrane is then welded to the rondelles with a hot-air blower. Panels are overlapped 150 mm and hot-wedge welded at 300 – 420 °C. Waterstops and injection connections are installed at block joints. All work is performed by certified Naue installation specialists.
Naue is a full member of the Arbeitskreis Tunnelabdichtung e. V. and is certified to its quality standards. Installation teams are trained and certified specialists. Naue holds relevant product approvals for Carbofol® geomembranes.
The full system comprises: Secutex® protection geotextile, Carbofol® Tunnel Membrane 2.0, Carbofol® Rondelles (predetermined breaking point), Carbofol® ME Anchor (non-penetrating), Carbofol® Click System (injection connections), Carbofol® Waterstops with injection hose connections, and Bentofix® X types for secondary sealing zones where required.
In a drained tunnel, seepage water is collected and discharged via drainage elements (pipes, channels) behind the membrane system - the membrane operates under low to zero hydrostatic pressure. In an undrained tunnel, the membrane must resist the full hydrostatic head; Carbofol® Waterstops segment the system into independently watertight compartments. The choice is determined by the hydrogeological conditions, acceptable maintenance regime and client requirements for groundwater discharge.
All Carbofol® seams are produced using state-of-the-art dual-channel hot-wedge welding equipment, which creates two parallel seams with an air channel between them. Each weld is pressure-tested immediately by inflating the air channel to a defined test pressure; a maintained pressure confirms a watertight seam. All weld tests are documented in a weld log per panel, forming part of the quality assurance (QA) dossier submitted at project completion. Certified Naue installers provide full weld documentation as standard.
The dimensioning of Carbofol® tunnel waterproofing systems is based on recognised national and European standards. Naue provides project-specific material sizing as a full service. Specialists assess ground conditions, water chemistry, hydraulic pressure and construction method to specify the correct membrane thickness, geotextile mass per unit area and accessory components.
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