Tunneling
Waterproof Protection Layers
Protecting tunnel waterproofing systems from puncture, abrasion and long-term mechanical stress.
Geotextiles in waterproofing and protection systems for tunnels
In tunnels, non-woven geotextile plays a key role in what is known as the ‘waterproofing blanket system’. It acts as a puncture-resistant layer that protects the membrane whilst ensuring hydraulic stability and the long-term watertightness of the tunnel.
After excavation and the application of shotcrete (the first phase of sprayed concrete), the surrounding rock mass or soil continues to release water.
If the water were to encounter a rigid, impermeable barrier with no means of drainage, it would accumulate behind the structure, creating significant hydrostatic pressure.
This pressure can exert force on the final concrete lining, causing cracking, delamination, water ingress into the tunnel’s soffit and even accelerated structural deterioration.
Key Benefits
- Puncture protection: Positioned between the primary sprayed concrete lining (which is often uneven and rough) and the synthetic geomembrane (made of PVC-P or TPO), it prevents the membrane from being punctured.
- Interlayer drainage: It channels seepage water from the rock or ground towards the piers and bottom drains, preventing the build-up of hydrostatic pressure on the structure.
Example of a Layer Structure
In tunnel waterproofing systems, nonwoven geotextiles are commonly installed directly behind the waterproofing membrane. Their role is to protect the membrane from the rough tunnel surface and support long-term system performance.
- Excavated tunnel surface or shotcrete layer
The prepared tunnel surface that forms the outer structural support of the underground construction. - Nonwoven geotextile protection layer
Installed against the tunnel surface to cushion and protect the waterproofing membrane from puncture, abrasion and localised stress. - Waterproofing membrane
The barrier layer designed to prevent water from entering the tunnel structure. - Inner concrete lining
The structural lining that forms the finished tunnel interior and protects the waterproofing system.
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