High-performance drainage solution for tunnels

When planning and constructing cut-and-cover tunnels or bored tunnels, a long and safe service life is a key priority. One of the factors affecting the performance of tunnels is the design of their drainage system. The installation of EnkaDrain geocomposites has proven highly effective in draining off water while also protecting the tunnel sealing system. For several decades now, different types of EnkaDrain have been proving their capabilities in terms of discharge capacity and compression resistance in tunnels and galleries all over the world. Examples of projects successfully completed with EnkaDrain include the Gotthard Base Tunnel (Switzerland): This is the world’s longest and deepest tunnel.

This is EnkaDrain for tunnel drainage

EnkaDrain tunnel drain Copyrights Low & Bonar_Enka Solutions (4)The EnkaDrain product range offers a number of low-inflammability drainage mats developed and extensively tested for use in tunnelling. What all EnkaDrain product variants have in common is their design – a durable drainage core made of polymeric monofilaments connected to one or two nonwoven filter fabrics. The voids ratio of the core exceeds 95 %, and this provides EnkaDrain with a long-term high discharge capacity despite overburden pressure. The core and filter nonwoven of Enkadrain 5020Z/2 contain fire retardants. This drainage mat meets fire class 5.1 (Swiss leaflet 1: BZK). It has been approved for the Swiss Gotthard- and Lötschberg Tunnel following testing by AlpTransit. Environments in which its resistance has been evaluated include hot water, heated acid and continuous compressive stress on rough surfaces.

How EnkaDrain contributes to a long service life of tunnels

In cut-and-cover tunnels, EnkaDrain is installed on the outside faces of the tunnel. It acts as a combined protection and drainage layer on top of the waterproof lining. In bored tunnels, EnkaDrain is applied directly on the unfinished sprayed concrete coating of the rock face to create a hollow space between the shotcrete and the liner. EnkaDrain so reliably drains off seepage water while also providing protection to the sealing. One product requirement in this particular application is that the drainage and protection layer must be capable of conforming to the irregularities of the tunnel walls: a requirement that EnkaDrain meets easily. Repair systems are a third application: here, single-sided EnkaDrain CK is used as a grip layer for sprayed concrete. All EnkaDrain drainage mats are lightweight, and easily and quickly installed even at low temperatures.

What makes EnkaDrain the ideal tunnel drain


  • Successfully applied in tunnels for over 30 years
  • Approved by authorities such as AlpTansit Gotthard
  • Excellent long-term drainage capacity
  • High compressive strength
  • Flexible
  • Low inflammability


  • Multifunctional product: drainage and reliable protection of the liner
  • Can also be used as a grip layer for shotcrete lining
  • Cost-efficient solution
  • Easily conforms even to complex rock profiles
  • Very easy to handle and install
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