Waterproof Tunnels with High-Performance EPDM Systems

Yes. EPDM is used in high-speed rail tunnels throughout Europe, including on the Lyon-Turin line and various TGV network tunnels in France. Seismic resistance (300-500% elongation), durability under high-frequency cyclic vibration without accumulated permanent deformation, and the 100+ year design service life are the principal reasons for selecting it over alternatives such as PVC or sprayed concrete. In Portugal, EPDM specification is aligned with the requirements of the high-speed rail programme and Ferrovia 2020.

EN 13491 defines performance classes for geosynthetic barriers in underground structures: Class A (≤ 50 kPa, shallow structures with low groundwater table), Class B (≤ 100 kPa, standard cut-and-cover in normal conditions), Class C (≤ 200 kPa, bored tunnels with moderate groundwater table — 15-20 m above invert), and Class D (≤ 400+ kPa, tunnels beneath rivers, deep metro, estuary crossings). The class is determined by the design groundwater level from geotechnical investigation. Membriko reviews the geotechnical report and proposes the appropriate class before any thickness or product specification is established.

Membriko carries out two complementary verifications. Metal probe testing traverses 100% of installed seams — any unbonded zone is detected immediately and repaired before advancing. For critical projects (Class D, or tunnels with specific contractual provisions), air lance testing of lap seams is specified as an additional QA measure, with each seam pressurised and checked for watertightness. All results are photographically documented and integrated into the as-built package delivered to the client. Secondary lining concrete placement is not authorised without documented 100% seam conformity.

In Membriko's compartmentalised system, repair of a compartment with active infiltration is carried out by injection from inside the tunnel, with no excavation or demolition. The process: (1) confirmation of the affected compartment by injection port pressure testing; (2) material selection — micro-fine cement grout for compartments with moderate void volume, or hydro-expanding polyurethane foam for active infiltration during injection; (3) progressive injection monitoring pressure and volume; (4) sealing confirmation by pressure test after material cure. Cost is €2,000-10,000 per compartment versus €50,000-500,000 for demolition and re-casting. The operation is completed in 1-3 days without tunnel closure.

EPDM contains no chlorine, so it does not emit hydrogen chloride (HCl) in case of fire — unlike PVC membranes, which contain 57% chlorine by mass and generate HCl at concentrations immediately dangerous to life (> 35 ppm). In terms of fire reaction behaviour, EPDM is classified Euroclass D or E per EN 13501-1. For tunnels with high fire safety requirements (metro, rail, high-volume road tunnels), Membriko specifies halogen-free low-smoke EPDM formulations achieving Euroclass D or C classification — the appropriate standard for the post-Mont Blanc fire safety environment.

In NMT (New Austrian Tunnelling Method), the membrane is installed freely between the primary sprayed concrete support and the cast-in-place secondary lining, with integrated drainage cavity and compartmentalisation system. This system accommodates structural movements without membrane stress. In cut-and-cover, the concrete box is constructed in open excavation and EPDM is applied on the exterior as a positive-pressure system before backfill, in pre-applied (concrete cast against membrane) or post-applied (membrane over hardened concrete) variants. Installation requirements differ significantly, but the EPDM material is the same — the difference lies in its position within the structure.

EPDM material cost is typically 10-20% higher than equivalent-thickness PVC. However, the 100+ year design service life of EPDM (no plasticisers to migrate) versus 50-80 years for PVC (with progressive plasticiser loss and associated elongation reduction), the absence of HCl emission in fire, and the superior elongation for seismic accommodation clearly justify the difference for a tunnel with a 100-year design life. In full life-cycle analysis, EPDM is invariably the more economical choice — Membriko provides this analysis in any specification consultation.

Yes. Membriko installs continuous infiltration monitoring systems integrated in the drainage cavity between membrane and primary support. Flow or electrical conductivity sensors in each compartment drainage channel detect active infiltrations with compartment-level precision — enabling preventive maintenance and injection remediation without tunnel closure. These monitoring systems are particularly relevant in critical infrastructure tunnels (metro, high-speed rail, Class I road tunnels) where any operational closure carries significant cost.