Sarnafil – a leading Switzerland-based manufacturer of roofing and waterproofing solutions – is looking forward to actively promote its range of high-quality and reliable solutions for tunnels in the region.

The company is highly active in Saudi Arabia, operating though Juffali Chemical Products/Sarnafil and Construction Materials Division.  In the UAE, it is represented by the Dubai-based Desert Roofing and Flooring.
“Our products and systems give long years of functionality and service because they are based on our own exacting standards and meet the demands of modern construction and civil engineering,” says a company spokesman.
“We offer customised solutions that fully conform to the requirements of a given problem. Every tunnel is unique, with different construction and hydro-geological conditions. This affects the choice of waterproofing system, as do many other factors,” he adds.
More than 35 years of experience in tunnel waterproofing has gone into the design of a range of Sarnafil waterproofing systems that include:
• Drainage system: Partial or umbrella waterproofing with connection to a drainage system;
• Waterstop system: Full, single-layer waterproofing with waterstops (injectable); and
• Active-control system: A two-layer line including an injection system. It can be vacuum-tested.
The use of polymeric waterproofing membranes to protect structures extends the service life of the concrete and contributes significantly to the preservation of infrastructure. Full waterproofing offers an additional advantage: long-term protection of the groundwater against contamination that could arise with tunnel use, he says.
Drainage system
Sarnafil’s drainage solutions for excavated tunnels meet the high standards of quality and reliability that engineers and owners expect. In addition, they are easy for the contractor to install, says the spokesman.
“At the heart of this system is a multifunctional drainage profile, which not only receives the perforated drain pipe, but also holds the gravel filter bed in place on one side, and serving as a form, holds the concrete slab on the other,” explains the spokesman. “This separation between gravel and concrete is crucial. Keeping cement out of the gravel greatly reduces sedimentation and calcification in the drainpipe. And that means lower maintenance costs.”
The Sarnafil drainage profile was first used in Rennsteig Tunnel, the longest highway tunnel in Germany.
Waterstop system
Turning to other Sarnafil systems, the spokesman says: “Tunnels subject to hydrostatic pressure must meet tough requirements. If groundwater infiltrates, it can cause damage, restrict tunnel service, or even force the tunnel to be closed. So these tunnels need a waterproofing system that gives all-around protection, like the Sarnafil Waterstop system.”
This system features elastomeric waterstops combined with a built-in injection system. The waterstops seal the joints between tunnel sections. The injection system, which can restore watertightness during use, is used to fill the cavity between liners during construction. The grout injection not only fills out the calotte, but also puts a smooth finish on the outside of the inner concrete liner. This smooth surface is critical as it keeps the waterproofing membrane from getting punctured when the groundwater presses the membrane against the concrete substrate, the spokesman points out.
Therefore, waterproofing must not be considered in isolation, but rather in conjunction with the adjacent elements of the structure and the various influences that act upon the membrane, he says.
The injection principle of the Waterstop System serves two purposes:
The sector nozzles are used to fill in between the membrane and the rear of the inner concrete liner (including injection at the crown). This ensures full embedment of the waterstop anchors and smoothes out the substrate against which the membrane will be pressed. The lines to the waterstops can be used to carry a resin injection to grout small areas of incomplete concreting.
The system is used to grout any leaking sectors after the well points are deactivated.
“No matter how carefully the work is carried out, the inner liner cannot be concreted perfectly, he says. “If faulty areas come into contact with the waterproofing system, there is a risk that the membrane can become damaged under hydrostatic pressure during service. If the concreting is incomplete along the waterstop anchors, water will be able to run around the waterstop, defeating the compartmentalisation at the block joints. If this happens a leak cannot be localised.”
In the Sarnafil Waterstop system, injection nozzles are installed with 21 mm-diameter lines on the waterproofing or the protective layer. The lines run to the inside of the tunnel and serve as the means of access to the membrane or protective layer behind the concrete inner liner. Once the space between the inner liner and the membrane is filled out (compact grouting) and the well points deactivated -  if a leak is detected in a finished tunnel block - the seal can be restored by using the many available injection nozzles. This precautionary measure minimises the need for core borings and helps localise any leak, which might occur, he says.
Active-control system
Complex hydro-geological conditions demand custom-designed waterproofing methods and systems that deliver absolute dependability.
The ability to actively test the waterproofing seal opens unthought-of possibilities, and it greatly enhances reliability. With the Active-Control system, any leak can be located – even during the construction phase. This system includes two membrane layers installed in sectors, where the seal of each sector can be tested with vacuum pressure. Any damage caused while performing routine maintenance or repair work can be instantly detected.
The transparency makes everyone working on the tunnel more conscientious, more careful. The system not only allows testing sector-by-sector, it can restore the seal of any sector by injection if needed, he concludes.