Patent for cost-saving tunnel seal

A new cast-in rubber gasket corner joint system designed to reduce the risk of segment cracking during tunnel construction has secured a UK patent.

The new 'compliant compressible corner', developed by VIP Polymers, is designed to ensure consistent load performance along the perimeter of a tunnel segment gasket (TSG).

Most cast-in TSGs are made with conventional 'shot-joint' corners. During the moulding process, the rubber in these corners fills the compression cavities in the extruded gasket sections, creating a solid rubber corner. According to VIP, the new compliant corner joint is a simple innovation that could save the tunnelling industry both time and money. It eliminates the risk of pressure build-up at one or more of the gasket's corners during installation, which can contribute to segment cracking during installation.

VIP, based in Huntingdon, Cambridgeshire, UK specialises in rubber seals and gaskets for the tunnelling and water industries.

Sales and technical director Steve Casey said: "We are delighted that the innovative design and manufacture of our new compressible corner joint, which is used across our entire cast-in gasket range, has been recognised with a UK patent. An international patent is also pending."

"Segment cracking during tunnelling operations is a significant cause for concern for both tunnel designers and tunnelling contractors. It is this concern we directly sought to address when we set out to design this new corner joint."

"Our innovation has been very favourably received within the tunnelling industry, and has already been used in a number of tunnel-building projects, with excellent results. VIP's design has already been specified for use in future tunnelling projects."

"Tunnel segment cracking is a hidden cost in all tunnelling projects, through the need for post-installation repairs and other associated costs. By using our new corner joint, tunnelling companies can reduce the risk of TSGs contributing to these costs."