

Tunnel waterproofing and drainage: elements and execution process
- Category: Geomembranes
Index
On G & G® We are leaders in tunnel waterproofing and drainage, we were in charge of the first waterproofing project with PVC geomembrane in Mexico with the Huachinango highway tunnel project in 2009.
With the intention of sharing with you a little of our knowledge and experience in this field, we mention some important points to consider in any tunnel waterproofing and drainage project.
WHY IS A TUNNEL WATERPROOFING PROJECT REQUIRED?
There are numerous reasons why it is important to consider waterproofing and drainage in any tunnel construction project, among which we highlight the following:
- In winter, filtered water produces ice on the road, which is very dangerous for car traffic.
- As protection from the effect of ice in mouths and short tunnels.
- To protect from concrete leaching and / or destruction of masonry by water seepage.
- As protection of concrete against infiltration of aggressive waters (sulfates).
- Another important reason is because it lowers maintenance costs.
STAGES OF CONSTRUCTION OF A TUNNEL
The construction of a tunnel involves four stages:
- Tunnel excavation.
- Sustaining the gallery.
- Tunnel waterproofing and drainage.
- Definitive coating.
In this article we focus on stage three: tunnel waterproofing and drainage.
GENERAL ELEMENTS FOR WATERPROOFING TUNNELS
The tunnel waterproofing and drainage phase requires the following elements:
- Drainage pipes.
- Granular filler.
- Oberhasli drainage (geodrenes)
- Protection and drainage geotextile.
- Waterproofing geomembrane.
- Records.
- Separation geotextile and filter.
GEOSYNTHETIC ELEMENTS
If we focus on the geosynthetic materials required for the waterproofing and drainage of tunnels, we would speak of three types:
- Geodrenes
- Non Woven Geotextile
- Specialized geomembrane.


TUNNEL WATERPROOFING AND DRAINAGE PROJECT PHASES
This stage can have up to four phases:
- PRELIMINARY: Provisional plugging work or collection and conduction of water (Oberhasli system) to allow the execution of the intermediate and main.
- INTERMEDIATE: Application of concrete shot by mortars for provisional support and regularization of the support.
- PRINCIPAL: This phase consists of the installation of a geotextile and a synthetic sheet or PVC-P waterproof geomembrane.
- LATER: Complementary works to the main waterproofing.
MAIN PHASE OF WATERPROOFING AND DRAINING OF TUNNELS
Next, we describe the main characteristics of the main phase of tunnel waterproofing:
- It must resist the attack of the water for a long time.
- It must withstand the loads of the formwork and the substrate (rock mass).
- It will have to adapt to the support (irregular).
- The components of the WATERPROOFING must be rotproof, resist biological aging and chemically unalterable.
- The implementation must be simple, fast, rational and economical.


ELEMENTS OF THE MAIN PHASE
The most important elements of the main stage of tunnel waterproofing are the following:
- GEOTEXTILE: Works cAs a protection element, for mechanical damage and for the evacuation of seepage waters and relief of hydrostatic pressures.
- GEOMEMBRANE: Synthetic sheet as a waterproof element.
- DRAIN PIPES: For pressure-free evacuation of seepage water.
PROCESS OR EXECUTION OF TUNNEL WATERPROOFING
Without going into much detail, we can summarize the process of waterproofing tunnels with geomembrane in four main steps or actions:
- PLACEMENT OF THE GEOTEXTILE with washers and fastener nails using mounting trolley.
- PLACEMENT OF THE GEOMEMBRANE on the geotextile, “hanging” it from the washers.
- OVERLAP WELDING of the geomembrane by means of thermofusion.
- PNEUMATIC TESTS as proof of quality control of the welds.
In addition to our vast experience, in G & G® We have the best geosynthetic materials and geomembranes on the market, which guarantees the durability of our tunnel waterproofing system.