Sealing in railway earth structures refers to the installation of a low-permeability barrier in railway embankments, cuttings and associated earthworks. It prevents railway runoff, which can carry fuel, herbicides and de-icing agents, from reaching groundwater. Naue supplies the complete layer system: Bentofix® geosynthetic clay liners (GCL) and Carbofol® HDPE geomembranes as the sealing element, and Secutex® nonwoven geotextiles as the protection layer above and below. Each component holds a DB HPQ for its application case under DBS 918 039.
Naue sealing and protection systems are installed wherever railway infrastructure crosses or borders groundwater-sensitive areas.
Sealing new and existing embankments to keep railway runoff away from groundwater.
Approved sealing systems for rail routes through designated water protection zones.
Sealing and protection systems for new lines, including routes across karst terrain.
Sealing transition zones where slab track meets earthworks at tunnel portals.
The right sealing design depends on slope geometry, hydraulic load, groundwater sensitivity and the applicable approvals. Every Naue system combines a sealing element with a protection layer above and below it.
Railway earthworks expose liner systems to vibration, variable soils and short construction windows. The Naue layer system is designed for these conditions: the Secutex® R 901 DB protection nonwoven absorbs puncture forces from angular fill and provides the frictional interface needed to transfer horizontal forces from train traffic. The sealing element in between, either a Bentofix® GCL or a Carbofol® geomembrane, is selected to suit the slope geometry and the hydraulic load.
Practical advantages for site teams:
Step-by-step installation sequence:
Railway earthworks to DBS 918 039 require two distinct functions. The sealing element (GCL or geomembrane) controls the passage of water and contaminants. The protection element (nonwoven geotextile) preserves the sealing element against mechanical damage. Which sealing element is right depends on geometry and hydraulic load.
Key principle: The sealing layer controls the water. The protection layer protects the sealing layer. Both are required in railway earthworks under DBS 918 039.
Technical benefit: no welding; minimum 300 mm cover soil.
Technical benefit: seam integrity can be tested on site.
Technical benefit: two independent sealing principles in one build-up.
The table summarises the main selection criteria and the standard layer build-up for railway earthworks.
Note: All products used on Deutsche Bahn AG projects must hold a valid HPQ for their application case. For project-specific guidance, contact Naue EDD Engineering & Design Department.
| Criterion | GCL system | Geomembrane system | Composite system |
|---|---|---|---|
| Typical location | Embankment and cut slopes, irregular earthwork surfaces | Edge zones, planar areas, high hydraulic head | Karst terrain, particularly sensitive water protection zones |
| Sealing principle | Swelling sodium bentonite; self-sealing longitudinal overlaps | Welded 2.0 mm HDPE, textured on both faces | GCL and geomembrane as dual barrier |
| Key value | k10 = 1.2 × 10⁻¹¹ m/s (EN 16416) | Testable welded seams; resistant to hydrocarbons, de-icing salts and heavy metals | Combination of both sealing principles |
| Installation | Unroll, min. 300 mm overlap, no welding; min. 300 mm cover soil | Welding to DVS 2225-4; seam testing by air pressure or vacuum; cover soil as per design | As per ZiE design |
| Protection layer | Secutex® R 901 DB above and below | Secutex® R 901 DB above and below | Secutex® R 901 DB above and below |
| DB approval | HPQ case 3.11 + case 3.13 | HPQ case 3.12 + case 3.13 | ZiE (EBA) + HPQ cases 3.11, 3.12, 3.13 |
| Recommended products | Bentofix® NSP 5400 DB, Secutex® R 901 DB | Carbofol® HDPE 406 2.0 F/F DB, Secutex® R 901 DB | Bentofix® NSP 5400 DB, Carbofol® HDPE 406 2.0 F/F DB, Secutex® R 901 DB |
These benefits come directly from how the Naue products work in this solution, and what they mean in practice for your project.
DB HPQ for every layer
Bentofix® NSP 5400 DB (case 3.11), Carbofol® HDPE 406 2.0 F/F DB (case 3.12) and Secutex® R 901 DB (case 3.13) hold valid HPQs under DBS 918 039. This removes approval uncertainty at tender and construction stage.
Less material to handle than a compacted clay liner
A GCL is installed in a layer of 5-10 mm, compared with 300–500 mm for a compacted clay liner. No compaction equipment is required, and cost savings of up to 40 % compared with a compacted clay liner are achievable, depending on the project.
Sealing element protected against railway loading
Secutex® R 901 DB absorbs puncture and abrasion from angular fill and transfers horizontal forces from train traffic at the interface. Its protection efficiency is tested to EN 13719.
Single-source system with consistent documentation
Sealing element and protection layer come from one manufacturer, with matching installation guidelines and approval documentation available from the start of the project.
Sealing in railway earth structures describes the installation of a low-permeability barrier in railway embankments, cuttings and associated earthworks. It prevents railway-related contaminants such as fuel, herbicides and de-icing agents from reaching groundwater. The system consists of a sealing element, either a geosynthetic clay liner (GCL) or an HDPE geomembrane, with a nonwoven protection layer above and below.
Naue supplies all layers of the system. Bentofix® NSP 5400 DB is the GCL for slopes and irregular surfaces (DB HPQ, application case 3.11). Carbofol® HDPE 406 2.0 F/F DB is the welded geomembrane for edge zones and high hydraulic head (case 3.12). Secutex® R 901 DB is the protection nonwoven installed above and below the sealing element (case 3.13).
A Bentofix® GCL is generally the more practical choice on slopes and irregular earthwork surfaces, where its self-sealing bentonite and needle-punched structure suit difficult geometry. A welded Carbofol® geomembrane is preferred where seam integrity, high hydraulic head or chemical exposure are decisive, for example in edge zones or contaminated-land crossings. In karst terrain or particularly sensitive zones, both can be combined under a case-by-case approval (ZiE).
Angular fill, sub-ballast and dynamic train loads can puncture or abrade a geomembrane or GCL. The Secutex® R 901 DB protection nonwoven absorbs these forces and, in full contact with the liner, transfers horizontal forces at the interface. DBS 918 039 application case 3.13 makes the protection element a mandatory part of the system, and RIL 836 requires a minimum mass per unit area of 500 g/m².
DBS 918 039 defines application cases for geosynthetics in railway construction, and manufacturers need a DB HPQ for each case. Case 3.11 covers clay liners (GCL) as the sealing element, case 3.12 covers geomembranes as the sealing element, and case 3.13 covers the protection element for both. A compliant system therefore combines case 3.11 or 3.12 with case 3.13.
The main frameworks are DBS 918 039 (technical delivery conditions for geosynthetics in railway construction), RIL 836 / DS 836 (DB guideline for earthworks) and the German Federal Water Act (WHG) for water protection zones. Geomembrane welding for DB applications follows DVS 2225-4. Relevant test standards include EN 16416 (GCL hydraulic conductivity), EN 13719 (protection efficiency), EN ISO 12236 (static puncture) and EN ISO 12957-1/-2 (shear strength).
The lower Secutex® protection nonwoven is placed on an even subgrade. Bentofix® is then unrolled with a minimum 300 mm overlap and needs no welding, while Carbofol® panels are welded to DVS 2225-4 by certified welders and the seams are tested by air pressure or vacuum. The upper Secutex® layer and the cover soil follow, with at least 300 mm of cover on Bentofix®. The Naue installation guideline must be available on site, as required by the EBA.
In many projects, yes. A GCL is installed in a layer of 5-10 mm, whereas a compacted clay liner requires 300-500 mm of selected clay placed and compacted in lifts. Savings of up to 40 % compared with a compacted clay liner are achievable. The actual cost difference depends on the project, including clay availability, transport distance and slope geometry.
Yes. All system components hold DB HPQ for their application cases, and the systems are designed for rail routes through water protection zones in line with WHG requirements. On the Wendlingen–Ulm high-speed line in Germany, where the route crosses the karst of the Swabian Alb, around 70,000 m² of Carbofol® HDPE 406 2.0 F/F DB were installed between around 140,000 m² of Secutex® R 901 DB protection nonwoven.
Sealing and protection systems for railway earthworks are designed in accordance with DB AG standards and national water protection legislation. Naue Engineering & Design Department (EDD) assists with specification from outline design to tender documentation:
The following system benefits come directly from how the Naue products work within the layer structure:
Naue Bentofix® is a geosynthetic clay liner (GCL) for waterproofing in landfill engineering, groundwater protection and hydraulic applications.
Naue Carbofol® is a HDPE liner for landfill sealing, mining containment, and groundwater protection.
Naue Secutex® is a mechanically bonded nonwoven geotextile for separation, filtration and protection for the use in roads, railways, environmental and hydraulic engineering projects.
