Project Description


Stuart Carson – Great Britain

01455 299758

Combining the advantages of a solid dowel and a secure threaded connection, this self-locking plastic connector provides a superb circle joint fixing for tunnel linings.

Suitable for use with packings, hydrophilic seals and EPDM compression gaskets, it is fast and easy to build and has no pockets/recesses to fill.


The Tunnelock circle joint connection has been developed over many years to provide the ideal connection between tunnel rings. Manufactured from a high strength durable plastic, it combines the advantages of a bolted connection with the speed, economy and alignment characteristics of a dowel. The system has been developed in conjunction with major tunnelling contractors and is suitable for use in traditional open face shields or with the latest full-face tunnel boring machines. The dowels allow a very fast ring erection sequence and are designed to reduce lipping between segments. The secure interlocking system is tolerant of a dirty environment and allows for the initial misalignment of segments to compensate for tapered joints and gaskets. Therefore, it is suitable for use with all types of tunnel rings and, in particular, with the trapezoidal segment rings. It has been used in some of the worst soft ground tunnelling conditions in the U.K. Technical data is available upon request.

Major advantages

  • Highly durable connection with no corrodible parts
  • Fast ring construction
  • Minimum building clearance (50mm standard, 75mm heavy duty) allows the use with most types of tunnelling machine and ram length
  • The rigid dowel action of the coupler re-aligns the segment and minimises the stepping of joints
  • No extra reinforcement required
  • Suitable for trapezoidal segment rings
  • Simple and easy to use
  • Does not induce bursting forces in the concrete
  • No circle joint pockets to fill
  • Suitable for use with all types of sealing systems, including EPDM compression gaskets and hydrophilic seals • Self-locking
  • Self-aligning