Dextra America, Inc. -Ground Engineering - Tunneling & Mining - ASTEC™ Soft-Eyes


Specific tunneling application of GFRP rebar cage allowing a TBM to break through a reinforcement cage in a minimum time.

Category: mining equipment | rebar cages | tunnel liners...

MasterFormat: Tunneling and Mining | Tunnel Excavation | Tunnel Support Systems...

Dextra America, Inc.
10317 SE 273rd PL
Kent, WA 98030
Tel: (206) 742-6020

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Ground Engineering - Tunneling & Mining - ASTEC™ Soft-Eyes

Specific tunneling application of GFRP rebar cage allowing a TBM to break through a reinforcement cage in a minimum time.

Tunnel breakthrough made easy with FRP rebar

ASTEC Soft-Eyes allow the penetration of Tunnel Boring Machines (TBM) through diaphragm walls and secant piles. This unique technology uses cut-able Glass Fiber Reinforced Polymer (GFRP) reinforcement as an advantageous replacement for conventional steel rebars.

The Soft-Eye technology has been developed by Dextra in 1996 and successfully implemented for the first time on Bangkok MRT subway stations. The Soft-Eye technology has since become a standard concept in the design of launching/receiving shafts and subway stations. We have successfully supplied over 500 Soft-eyes on all continents.

Dextra offers an integrated turn-key solution which includes design, optimization, manufacturing, logistic and on-site training.

Where and why using Soft-Eyes?

  • In each D-Wall or Pile where a TBM will go through, typically in launching/retrieval shafts or subway stations.
  • Although designed as a temporary solution, a Soft-Eye can stay in the ground up to 100 years!
  • Thanks to the cut-able nature of GFRP bars. TBMs can get in/out of shafts/stations in a few minutes.
  • With Soft-Eyes, forget about the tedious and unsafe task of removing steel reinforcement. No risk either of damage for the TBM’s head .
  • Dextra Soft-Eyes follows ACI construction guidelines. Our solution is backed up by world’s major consulting firms.

Design to breakthrough : Dextra follows and assist you through every step of the way.
Time-saving : Let TBM go through in minutes while avoiding any damage.
Corrosion-free : Tunneling delayed? Dextra Soft-Eyes can stay in the ground up to 100 years!

Turnkey solution by Dextra

  • Dextra delivers a full solution: design, optimization, manufacturing, logistic and on-site training of your teams.
  • Suitable for all ground conditions and adaptable to D-Walls and circular piles.
  • Various customized shapes (straight, C-shape, loop) and grades (elastic modulus 45 GPa and 50 GPa) available.
  • Splicing systems also available if required.
  • Accelerated delivery schemes available for the most urgent projects.
  • Wherever soil forces require it, Soft-Eyes can also be combined with ASTEC Active Anchors, which are also fully cut-able.

Cut-able solutions

Cut-able support is mostly used in the longitudinal direction of the tunnel (portal, face) when temporary stabilization is required before moving to the next phase. Also, Mechanized Tunneling is becoming standard in urban areas, especially for underground metro projects. This modern technique is calling for new kind of systems, in particular cut-able reinforcement bars for concrete structures (like Soft-Eyes in D-walls) and cut-able ground anchors.

Radial & lateral support (Roof & Wall)

When building a tunnel by drill & blast or conventional mining, the roof and walls need to be supported. Rock-bolts are the first type of support installed, before any other kind of mesh or lining is applied. Depending on the construction sequence and technology, both temporary and permanent bolts can be offered.

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