Tunnelling – Reinforcement

GFRP Bar & Stirrups

The GFRP BAR and Stirrups are successfully used to replace the traditional reinforcement bar within concrete structures in temporary tunnelling works (D-walls, retaining walls, piles and the like) e.g. within the tunnel breakthrough, the so-called ‘soft-eye’.

The GFRP BAR CRG reinforcement elements are made from reinforced polyester resin matrix, together with a unidirectional Glass Fibre (GFRP type E-Glass) continuous thread profile.

The GFRP BAR CRG provides the following advantages:

– Extremely high tensile strength
– High flexural strength
– High shear strength
– Extremely high modulus
– Significant enhancement of the friction effect (pull-out effect)
– Cuttability
– High corrosion resistance

GFRP CRG Bolt

Used in tunnelling works, our GFRP CRG fibreglass bolt is equipped with a steel head for post-tensioning and is used in rock bolting, soil nailing and ground anchors. It is made of a reinforced polyester resin matrix, together with a unidirectional glass fibre (GFRP type E-Glass) continous thread profile. The thread process does not affect the glass fibre integrity, with significant enhancement of both fiction effect (pull-out), and overall tensile strength capacity.

The steel head is sized according to the mechanical performance of the specific profile on which it is installed. The tensioning system is fast and effective and is calibrated to ensure the integrity of the GFR profile.

It is also possible to connect two elements by a S355 steel sleeve.

The GFRP BOLT CRG is recommended for temporary application only (ACI440.1R, refers).

GFRP Pipes & Elements

GFRP Pipes are used for ground reinforcement in tunnelling works, wherever significant enhancement of the ground characteristics are required, e.g. within the tunnel face ahead of the excavation, the so-called ‘core consolidation’.

GFRP tubular elements (pipes) are made from a reinforced polyester resin matrix, together with a unidirectional Glass-Fibre (GFRP type E-Glass) continuous thread profile. The thread process does not affect the glass fibre integrity, with the resultant benefit of significant enhancement of both friction-effect (pull-out), and overall tensile strength capacity.

The units are inserted into a pre-drilled hole in the excavated ground and grouted. The corrugated profile improves bond strength, which when coupled with the high tensile capacity of the pipe provide reliable face stabilisation and reinforcement for tunnelling clients.

The tubular elements (pipes) may also utilise couplings to extend pipe length and Manchette injection sleeve during the grouting operations. GFRP Pipes and other elements are recommended for temporary applications only.

P.E.R. Ground System

The P.E.R. Ground System (Pressurizing Element for Reinforcement of the Ground) series has been engineered to provide tunnelling clients with cost efficient ground improvement in difficult and adverse conditions. The system is fully customisable and can solve multiple tasks simultaneously; drainage, reinforcement and soil consolidation. It is used in loose, swelling or ravelling ground and also where stringent requirements in underground water control are imposed.

P.E.R. Ground features a polyester resin and fibreglass reinforcement element, with an integral expanding sheath. Once inserted into a drill hole, the sheath is filled with grout under pressure. This enhances the friction effect (pull-out), the bond between grout and reinforcement and overall grout volume control.
The product may be customized when used in core-consolidation face applications:
– Micro-slotted HDPE pipe, and non-woven geotextile, to allow recompression of the ground and drainage simultaneously
– Slotted PVC pipe (manchette pipe), to allow recompression of the ground and either permeation, or pressure grouting simultaneously GFRP Pipes and other elements are recommended for temporary applications only.

Steel Bolt

Our E-EXBOLT is a rock bolt for use in (but not limited to):
– Mining applications such as hanging wall and roof bolting
– Tunnelling applications such as radial systematic bolting
– Rock slope stabilisation
It is made of a welded metallic tube, longitudinally crimped (folded in on itself) and sealed at one end. The bolt is expanded inside a pre-drilled borehole using a high pressure water flow from a pump. The installation process is easy and very similar to other rock bolts. This makes E-EXBOLT readily usable by all operators.

E-EXBOLT provides the following advantages:

– Bonding to the rock results from the friction which is formed between the expanded bolt and the rock
– Friction bolts can be subjected to the full load directly after they have been positioned and are immediately able to absorb rock movements
– Bearing force is applied along the complete length of the inserted bolt


E-EXBOLT friction bolts supplied in steel grade S355 MC.