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Waterproofing systems for tunnel structures are faced with very stringent requirements regarding durability, exposure and stress conditions, demanding construction methods and sequences, ease of application and total cost management. In addition, sustainable system solutions are becoming more important to save natural resources such as energy and water, while reducing CO2 emissions.
Content Index
Main Challenges in Tunnel Waterproofing
Today, operators request a service life for underground structures of over 100 years. However, a lack of watertightness severely reduces the long-term durability of a tunnel structure and poorly affects its planned use, as water ingress and other exposures result in physical attack and deterioration of the concrete. This may result in expensive repair work, damage and even operational downtime.
The selection of the appropriate waterproofing solution, the project specific design of the chosen waterproofing system and its safe application on site are the key elements to minimize operational costs. A waterproofing system typically amounts to a fraction of the total constructions costs. The selection of a high-quality waterproofing solution may easily save an amount of its initial investment or more on future maintenance and repair costs during the entire service life of the structure.
Tunnel Excavation Methods & Waterproofing Concepts
Tunnels face a variety of exposures and stress including water ingress, dynamic forces, temperature variations, chemical and even gas penetration. There are also a variety of methods for excavating tunnels.
All these factors in addition to location, geology and groundwater conditions define the appropriate approach to the tunnel design. The tunnel engineer or designer must understand all factors, prior to defining the construction layout and selecting waterproofing materials and systems.
Sika Solutions for Tunnel Waterproofing
As the global leader in providing structural waterproofing solutions, Sika has a complete and comprehensive range of solutions and designed systems to meet the specific needs and requirements of owners, architects, engineers and contractors on site.
Sika tunnel waterproofing solutions include:
Highly flexible membrane systems
Liquid-applied polymeric membranes
Waterproofing concrete admixtures
Joint waterproofing systems
Waterproofing mortars and coatings
Injection grouts
For our full range of all tunneling solutions beyond waterproofing, please visit our tunneling solutions webpage.
Five Main Types of Tunnels & Selection Guide
Before selecting the specific waterproofing solutions, we must understand which type of tunnel is designed and planned for the project.
Mined tunnels include all structures excavated underground by conventional methods or tunnel boring machines (TBMs). These include drained tunnels (umbrella), pressurized tunnels and the connecting cross-passage tunnels.
Cut-and-cover structures, often used for station boxes for transit stations, describe buildings constructed in an open pit and then covered by soil again. The type of temporary pit support and excavation method defines the possible waterproofing systems to be used, whether box-in-box or permanent diaphragm walls are used.
1. Drained Tunnel (Umbrella)
A drained tunnel uses an umbrella concept, where the waterproofing layer protects the inner structural concrete by directing the water into drainage pipes located on each side of the tunnel.
Selection Table for Drained Tunnel Solutions
| Fully-bonded membranes | SikaProof®-200 | (+) |
| SikaProof®-110 PP-500 | (++) | |
| SikaProof® A+ | (-) | |
| Loose-laid membranes | Sikaplan® WP 1100 | (+) |
| EVA cementitious membranes | Sikalastic®-245 | (+) For tunnels with low requirements, e.g. escape tunnels |
| Legend | |
| (++) | Recommended application |
| (+) | Possible application |
| (-) | Not recommended |
2. Pressurized Tunnel
Pressurized tunnels are under full water pressure, which must be considered in the structural design. The waterproofing layer protects the entire structural concrete against water ingress and chemical attacks.
Selection Table for Pressurized Tunnel Solutions
| Fully-bonded membranes | SikaProof®-200 | (++) |
| SikaProof®-110 PP-500 | (+) | |
| SikaProof® A+ | (-) | |
| Loose-laid membranes | Sikaplan® WP 1100 | (+) |
| EVA cementitious membranes | Sikalastic®-245 | (-) |
| Legend | |
| (++) | Recommended application |
| (+) | Possible application |
| (-) | Not recommended |
3. Cross-Passage Tunnels
Cross-passages are an important feature of large tunnel users’ safety. Special care shall be taken to ensure continuous waterproofing in these areas, which may contain operating and maintenance equipment in addition to providing escape pathways.
Selection Table for Cross-Passage Solutions
| Fully-bonded membranes | SikaProof®-200 | (++) Termination with Sikaplan® WT Tape-200 |
| SikaProof®-110 PP-500 | (+) Termination with Sikaplan® WT Tape-200 | |
| SikaProof® A+ | (+) Termination with Sikaplan® WT Tape-200 | |
| Loose-laid membranes | Sikaplan® WP 1100 | (+) Termination with Sikaplan® WP Tape-200 |
| EVA cementitious membranes | Sikalastic®-245 | (-) |
| Protection of tunnel segments | Sikagard®-65 WN | (++) Only for the segments |
| Legend | |
| (++) | Recommended application |
| (+) | Possible application |
| (-) | Not recommended |
4. Station Box/Cut-and-Cover Tunnel (Box-in-Box)
This method involves the creation of a concrete structure within an existing concrete “box”. The waterproofing layer must be applied before the concreting of the base slab and after the concreting of the top slab. For vertical areas, the waterproofing layer is applied either before or after the concreting of the walls, depending on the site conditions.
Selection Table for Stations Solutions (Box-in-Box)
| Type | Blind-side waterproofing (e.g. base slab, wall) | Open-cut structure (e.g. wall, top slab) | |
|---|---|---|---|
| Fully-bonded membranes | SikaProof®-200 | (++) High water pressure | (+) Post-applied |
| SikaProof®-110 PP-500 | (+) | (-) | |
| SikaProof® A+ | (++) | (++) Post-applied | |
| Loose-laid membranes | Sikaplan® WP 1100 | (+) Compartment system | (+) |
| EVA cementitious membranes | Sikalastic®-245 | (-) | (-) |
| Hot-spray PUA membranes | Sikalastic®-851 | (-) | (++) |
| Sikalastic® M 800 Sikalastic® M 811 | (-) | (++) |
| Legend | |
| (++) | Recommended application |
| (+) | Possible application |
| (-) | Not recommended |
5. Station Box/Cut-and-Cover Tunnel (Permanent D-Walls)
Diaphragm walls (D-walls) are built as permanent structures, being a strong method of soil and water retention especially in poor conditions. With the introduction of the following solutions, the D-wall, the base slab and the top slab will be protected from water ingress.
Selection Table for Stations Solutions (D-Walls)
| Type | Base slab | D-wall treatment | Top slab | |
|---|---|---|---|---|
| Fully-bonded membranes | SikaProof®-200 | (++) High water pressure | (-) Use SikaInject®, Sika Waterbar®, SikaFuko®, SikaSwell® ... | (+) Post-applied |
| SikaProof®-110 PP-500 | (+) | (-) Use SikaInject®, Sika Waterbar®, SikaFuko®, SikaSwell® ... | (-) | |
| SikaProof® A+ | (++) | (-) Use SikaInject®, Sika Waterbar®, SikaFuko®, SikaSwell® ... | (++) Post-applied | |
| Loose-laid membranes | Sikaplan® WP 1100 | (+) Compartment system | (-) Use SikaInject®, Sika Waterbar®, SikaFuko®, SikaSwell® ... | (+) |
| EVA cementitious membranes | Sikalastic®-245 | (-) | (+) | (-) |
| Hot-spray PUA membranes | Sikalastic®-851 | (-) | (-) | (++) |
| Sikalastic® M 800 Sikalastic® M 811 | (-) | (-) | (++) |
| Legend | |
| (++) | Recommended application |
| (+) | Possible application |
| (-) | Not recommended |
