Drainage in railway backfill zones refers to the controlled removal of seepage water from the backfill behind railway structures such as retaining walls, bridge abutments and cut-and-cover tunnels. Water that cannot drain builds up hydrostatic pressure on the structure. Secudrain® geocomposites combine a drainage core with a filter nonwoven on both faces and replace a mineral drainage layer with a single layer a few millimetres thick. For DB projects, Secudrain® WAS 7 holds the DB HPQ for application case 3.10, drainage element for backfill zones
Secudrain® geocomposites are installed wherever seepage water must be removed from the backfill behind railway structures.
Drains the backfill of concrete retaining walls along the track.
Controls seepage water behind abutment walls of railway bridges.
Drains the backfill against tunnel walls and portal structures.
Slim-profile drainage behind platform edge walls.
The design of geocomposite drainage behind railway structures depends on the expected seepage, the earth pressure acting on the drainage element, the backfill material and the approval requirements of the railway operator.
Behind railway structures, the drainage element must carry water under the full earth pressure of the backfill, and its filter must stay open against fine-grained soil. Secudrain® is a three-layer, pressure-stable drainage system: a wave-shaped polypropylene core is bonded over its full area to a mechanically bonded Secutex® filter nonwoven on each face, so that shear forces are transferred between the layers.
Practical advantages for site teams:
Step-by-step installation sequence:
On the DB network, the use of geocomposite drainage elements in backfill zones is regulated by RIL 836. Outside the DB network, other requirements apply, for example RiZ-ING and ZTV E for bridge structures.
Key principle: A drainage element only works as long as its filter works. Behind concrete structures, it must also cope with alkaline pore water. On DB projects, only a product with HPQ for case 3.10 may be used.
Technical benefit: a thin drainage layer where space behind the wall is limited.
Technical benefit: calculable flow capacity as a basis for the coordination.
Technical benefit: the same installation method for railway and road structures.
The table shows the technical data of Secudrain® WAS 7 used behind railway structures.
For project-specific selection and the flow capacity calculation, contact Naue Engineering & Design Department (EDD).
| Criterion | Secudrain® WAS 7 |
|---|---|
| Typical use | DB projects (HPQ case 3.10); bridge structures to RiZ-ING / ZTV E |
| Construction | Wave-shaped PP core, filter nonwoven on both faces |
| Thickness at 2 kPa | 6.0 mm |
| Mass per unit area | 660 g/m² |
| Flow capacity md, i = 1.0 (EN ISO 12958) | 0.8 l/(m·s) at 20 kPa; 0.6 l/(m·s) at 50 kPa |
| Opening size O90 (EN ISO 12956) | 0.09 mm |
| Roll size | 1.90 m × 35 m |
| DB HPQ | Case 3.10 |
These benefits come directly from how the Naue products work in this solution, and what they mean in practice for your project.
Approved for DB projects
Secudrain® WAS 7 holds the DB HPQ for application case 3.10 under DBS 918 039 and is approved under RiZ-ING / ZTV E for bridge structures.
Calculable flow capacity
Flow capacities tested to EN ISO 12958 under defined pressure and gradient give planners a verifiable design basis for the drainage behind the structure.
A thin layer instead of gravel
A geocomposite 6-25 mm thick replaces a granular drainage layer of 300-600 mm and a separate filter geotextile. This can reduce the drainage layer material by up to 90 %, depending on the project.
Simple installation
Secudrain® is unrolled against the structure face and jointed using prefabricated overlaps. No drainage aggregate has to be supplied, placed or compacted.
Drainage in railway backfill zones describes the controlled removal of seepage water from the backfill behind railway structures such as retaining walls, bridge abutments and cut-and-cover tunnels. A drainage element against the structure face collects the water and leads it to a drain at the base, so that no hydrostatic pressure builds up on the structure.
DBS 918 039 regulates drainage elements for backfill zones as application case 3.10. According to RIL 836, a geocomposite may be used for the backfill drainage of retaining walls in justified individual cases. For backfills of railway bridges, its use requires consultation with the responsible DB technical department. In both cases, the product needs a DB HPQ for case 3.10.
Secudrain® WAS 7 holds the DB HPQ for application case 3.10. It consists of a wave-shaped polypropylene core with a filter nonwoven on both faces, is 6.0 mm thick and has a flow capacity of 0.8 l/(m·s) at 20 kPa and a hydraulic gradient of 1.0.
Pore water from concrete can raise the pH in the backfill well above the range of natural soils. The declared durability of geosynthetics typically refers to natural soils with a pH of 4 to 9. Behind concrete structures, the suitability of the drainage element therefore has to be confirmed for the specific conditions. On DB projects, a product with HPQ for case 3.10 is required.
The flow capacity in the plane of the geocomposite is tested to EN ISO 12958. At a hydraulic gradient of 1.0, Secudrain® WAS 7 carries 0.8 l/(m·s) at 20 kPa and 0.6 l/(m·s) at 50 kPa. The required capacity is calculated for each project from the expected seepage, the earth pressure and the gradient.
Yes. A Secudrain® geocomposite 6-25 mm thick replaces a granular drainage layer of typically 300-600 mm together with a separate filter geotextile. This can reduce the drainage layer material by up to 90 %, depending on the project. On DB projects, the RIL 836 conditions for case 3.10 apply.
Secudrain® is unrolled vertically against the structure face before backfilling, fixed at the top and jointed using the prefabricated overlaps. The lower end is connected to the drain at the base of the structure. The backfill is then placed and compacted in layers; the geocomposite should be covered within one month of installation.
On DB projects, DBS 918 039 (HPQ for case 3.10) and RIL 836 apply. Flow capacity is tested to EN ISO 12958, the opening size of the filter nonwoven to EN ISO 12956 and its water permeability to EN ISO 11058. EN 13252 defines the characteristics required for geotextiles in drainage systems. For bridge structures outside the DB network, RiZ-ING and ZTV E apply.
Yes. Secudrain® is used to drain the backfill against the walls of cut-and-cover tunnels and portal structures. It is installed against the structure before backfilling, in the same way as behind retaining walls. Naue Engineering & Design Department (EDD) provides project-specific design assistance.
The key design parameter is the in-plane flow capacity of the geocomposite under the earth pressure and hydraulic gradient at the structure. Naue Engineering & Design Department (EDD) assists with the flow capacity calculation and product selection:
The following system benefits come directly from how the Naue products work within the layer structure:
