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Fittings for Tunnel Segments

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FIP MEC offers technical solutions and fittings for TBM tunnels. In 35 years tunneling activity worldwide, FIP MEC has gained extensive experience and more than 130 references.

Specific accessories for tunnel lining segments are available: gaskets, dowels, guidance rods, customized bolts, adhesives, packers, lifting and grouting sockets.

Continuous research and innovation in partnership with specialized universities, companies and third laboratories allows the constant development of new products.

Typologies

Anchored Sealing gaskets

Anchored gaskets are the ultimate and more updated solutions obtained after a long and recognized journey on the scene of the sealing systems for concrete segments, proving how FIP MEC moves constantly forward to satisfy the growing technical requirement for mechanical excavated project. Anchored gaskets improves the production lead time of the precast activities, being directly fixed into the internal sides of the moulds before concreting.

The geometry of each profile is developed starting from FEM analysis on design stage. A proper test campaign is then performed in our internal avant-gard laboratory, withstanding international recommendations and certified accredited institutions.

FIP MEC anchored gaskets have several advantages:

  • Cleaner, faster and cheaper production cycle, if compared with the standard glued gasket. The use of adhesive, as well as gluing process, are no longer necessary.
  • Avoid environmental issues.
  • No specials equipment needed (for example gasket press).
    Higher tightness characteristics thanks to a double feet connecting system into concrete.
  • Avoid detachment risks during the installation of the segments, especially of the keystone.
  • Less leakage risks, as per maximized distance for water between gasket and concrete.
    Lower reaction force with higher sealing performances due to the specific geometry developed for the linear profile and in the corner area, in order to guarantee easy segments installation and avoiding case of spalling of the concrete.
  • Accurate, fast and easy installation, as per simplified linking edges perfectly fitted on the relevant groove into the moulds, avoiding concrete leakage during casting processes.

 

Gasket profiles are made of special EPDM compounds. Standard hardness is 70 Sh/A. Special hydro swelling cords are available and supplied in separate frames or rolls to be set into the EPDM profile. Customers are invited to consult FIP MEC who will propose the best suitable sealing profile.

Glued Sealing Gaskets

FIP MEC is one of the most competitive and skilled supplier of elastomeric sealing gaskets for tunnel segments and shafts. Over the years design and testing have been constantly improved. The company offers a wide range of innovative and reliable solutions for every type of tunnel lining design. Gaskets are supplied in frames and are specific for each tunnel segment. During the ring construction they are compressed ensuring the water tightness between segments. FEM analysis in the design stage are checked through several tests in the laboratory at short and long term. The sealing gaskets are customized products, customers are invited to consult FIP MEC who will propose the correct and best sealing profile and the associated groove. A proper test campaign is then performed in our internal avant-gard laboratory, withstanding international recommendations and certified accredited institutions.

FIP MEC glued gaskets have several advantages:

  • Extruded and vulcanized profiles are manufactured in up-to-date production lines. They have a proven record of durability, being resistant to chemical attack and degradation.
  • The load deflections curves responds to the highest market specifications.
  • All the profiles and soft discharged corners are particularly designed to minimize the reaction loads and overloads at the groove flanks. Frame soft corners are made in accordance with the angles and geometry of each specific segment.
  • Special anti-friction solutions on the short sides of the segments are available upon request.
  • FIP MEC has developed a very strong adhesive for the glued gasket frames.

 

Gasket profiles are made of special EPDM compounds. The combined gaskets in EPDM plus the hydro swelling cord are available in frames and rolls to be set into the EPDM profile. A wide range of profiles are available.

Biblock Dowel Systems

Biblock dowel system is a tough connection set designed and supplied by FIP MEC. The reliability of this system and the experience gained on site throughout the years are guarantee of success for every tunnel lining. The system, tested several times in lab and on site, ensures high shear and pull out resistances. Instead, the pull in forces needed to insert the pin into the sockets are very low, so it is very easy to install. Biblock ensures the perfect alignment of segments.

FIP MEC biblock dowel systems have several advantages:

  • Cost saving per mould/ring.
  • Quicker segment installation.
  • Safer site conditions.
  • Less personnel needed at the tunnel face.
  • Better segment alignment.
  • Smoother inner tunnel surface.
  • Lower water friction in hydraulic tunnels.
  • Dielectric isolation along the tunnel lining.

 

More than 4.500.000 Biblock have been supplied worldwide, even in several difficult tunnelling conditions. Different types of Biblock are available and based on the client’s needs.

Guidance Rods

The guidance rod allows the correct positioning and the longitudinal alignment of segments. It shall be glued into a suitable groove along the short side of the segment. FIP MEC guidance rod furthermore is capable of withstanding high shear forces. It is always recommended to manage tight tolerances. More than 1 300 000 FIP MEC guidance rods have been installed worldwide.

The guidance rod is made of recycled plastic. It is provided in different diameters, each of them specific for every tunnel diameter.

FIP MEC guidance rods have several advantages:

  • They help to ensure an accurate alignment between segments during their installation.
  • They allow a quicker segment installation.
  • They reduce the risk of concrete damages while installing adjacent segments.
  • They increases the shear resistance between elements of the same ring.

 

Guidance rods are available in a wide range of diameters. They are supplied in suitable length to meet the project specifications. Their installation is made through glue or special clips. Should specific diameter and length be required, FIP MEC can arrange them out of standard production.

Grout and Lifting Sockets

The grout and lifting sockets are threaded plastic products installed during the pre-casting of segments. Threaded grout plugs, cap sealing washers, hydro-swelling washers and plastic non-return valves are also available. A wide range of sockets of different diameters and lengths is available to meet the project requirements.

FIP MEC grout and lifting sockets have several advantages:

  • They represent safe options for segment lifting and handling.
  • They allow easy and functional injections from the intrados.
  • They can be customized in dimensions upon request.

 

FIP MEC grout and lifting sockets are made of resistant plastic materials. The socket main part and its accessories can be provided separately. They withstand high water pressures. Several pull out tests have been carried out to fix the extraction resistance, that increases with the socket dimensions.

The grout and lifting sockets are available in the here listed inner diameters. Standard lengths (L) may be customized. Different out of standard products were manufactured and others can be designed for special situations.

Bolt and Bolt Sockets

The bolts are often required as radial and circumferential connection system between segments of the tunnel lining. A wide range of hexagonal head bolts is available to meet the project requirements.

The plastic bolt sockets are installed during the pre-casting activities. The connection bolts are screwed immediately after the segment installation at the tunnel face. Washer are also required. FIP MEC can supply further special smaller bolts and relevant sockets used only to fix services without drilling the concrete at the intrados.

FIP MEC bolts and bolt sockets have several advantages:

  • They increase the shear and pull-out resistances on the radial connection joints.
  • They are useful in hydroelectric tunnels with high internal pressure.
  • They are a safe connection system between adjacent rings.
  • Bolts and washers are removable.
  • For hanging services only: no additional drills in concrete are needed.

 

The steel bolts and washers can be supplied black, electrolytic and hot dip galvanized. If the client needs spare bolts they can be black or electrolytic galvanized. Un-removable bolts in the tunnel lining should be hot dip galvanized or made in stainless steel. Washers made of plastic, grommets and bolt centering plastic accessories are also available. Plastic bolt sockets are made of tough plastic materials.

A wide range of connection bolts are available. The length is customized for each tunnel project. The available diameters are 20, 25 and 28 millimeters.

Miscellaneous

FIP MEC develops and supply also other useful fittings and accessories for the tunnel lining. Packers to spread the load of pushing rams, adhesives, foamy strips to prevent leakages, stainless steel grounding system and other tailor-made products designed under request.

Packers are strongly recommended in the construction of the tunnel lining. Shape and dimensions of packers are related to each specific tunnel segment. They are usually installed in the circumferential side of the segments, opposite the TBM advance. Despite they are available in different compressible materials, the experience earned by FIP MEC recommends the bituminous ones.

FIP MEC packers have several advantages:

  • Reduced concrete cracks.
  • They are flexible, water resistant, easy to apply.
  • They increase friction between segments of the tunnel lining.


Packers are made as requested by the customers. They are available in different shapes and sizes to suit specific requests of the designers. Standard lengths are up to 1 m. The packers shall be bonded to the concrete and FIP MEC adhesives are recommended. Self adhesive packers are also available. 

Adhesives ensure high quality bonding. They are particularly designed for gaskets, guidance rods, packers and any kind of fitting for tunnel segments. More than 700 000 liters of glue have been supplied worldwide as result of the practical experience of FIP MEC.

FIP MEC adhesives have several advantages:

  • are easy to apply by means of brushes or spray pumps.
  • are resistant at high temperatures.
  • are Toluene free.
  • need a short and appropriate dry time.


Adhesives bond difficult substrates as EPDM, plastics and different types of synthetic solid materials to be applied on the concrete surface. They can be stored for many months at suitable conditions.

Adhesives are tested both in the lab and at site to meet the project requirements. Many test results and applications have demonstrated that the glue of FIP MEC is one of the most cost-effective product together with high effectiveness and reliability.

Foamy strips are sealing profiles made by closed-cell polyethylene. They are mainly used as additional sealing system around the tunnel lining between the EPDM gaskets and extrados.

Grounding systems ensure the grounding connection between each element of the tunnel lining. Primary installed during the casting processes, then they shall be linked together from the tunnel lining intrados.