Cavidrain Protector

Cavidrain® Protector tunnel wall cavity drainage & lining system provides a free draining layer to collect infiltration water from behind tunnel linings, as well as providing protection from physical damage.

Cavidrain® Protector provides significantly more drainage capacity than traditional geotextile fleece solutions and can often be used to replace the fleece itself.


  • New tunnel construction
  • Repair of existing tunnels
  • NATM constructed tunnels
  • Drill and blast tunnels
  • TBM tunnels
  • Metro underground stations
  • Cable tunnels
  • Highway tunnels
  • Railway tunnels


  • Enhanced integrity of the tunnel lining system
  • Improved drainage capacity
  • Minimised damage caused by mineral calcification

The long term compressive strength of Cavidrain Protector is 250kPa. The cuspates provide a void for water flow.

Good tunnel design anticipates drainage needs by managing the build up of hydrostatic pressure on the waterproofing liners and by transporting water away in the tunnel invert. Tunnel wall drainage is conventionally provided by a layer of geotextile held in place by nails. Geotextiles offer little or no in-plane water flow, making them ineffective as a drainage layer. This limited drainage capacity is further impeded by the compressive forces at this location and the choking of the geotextile due to calcification.

Cavidrain® Protector is a pre-formed cavity drainage system. It is a highly flexible void forming sheet material developed to facilitate the relief of water pressure behind tunnel linings, thus giving hydrostatic protection to the membrane liner. It comprises a flexible thermoformed HDPE (high density polyethylene) sheet in the form of a dimpled profile.

Cavidrain® Protector provides significantly more drainage capacity and can be used to replace the geotextile, creating a free draining void to collect infiltration water from behind the tunnel waterproofing. This minimises the build up of hydrostatic pressure, protecting and enhancing the effectiveness of the waterproofing.

Cavidrain® Protector wall drainage is easily fixed to tunnel walls with shot-fired pins, and rondels for fixing of the waterproof liner.

Cavidrain® Protector has been used successfully throughout the world in a number of major tunnel projects.

Typical Client Profile

  • Medium to Large Contractors
  • Tunnel Contractors
  • Consulting Engineers
  • Tunnel Engineers
  • Waterproofing Contractors
  • Utility Service Providers
  • Railway Engineers

ABG Technical CPD Presentations

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Additional information

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