Over the past 20 years, Bluey has delivered waterproofing solutions across hundreds of cross-passages, consistently achieving the stringent “no damp patches” specification required for rail infrastructure. Cross-passage entrances present some of the most complex conditions in tunnel waterproofing. The geometry typically involves curvature in three planes, creating challenges for membrane installation, steel fixing, and concrete placement. These conditions increase installation complexity and result in a high density of welds across relatively small surface areas, placing greater importance on workmanship and detailing. One of the most critical aspects of cross-passage waterproofing is the termination of the membrane to TBM segments.

This interface must be engineered and executed correctly to maintain system continuity and ensure long-term watertight performance. As a result, significant research and development have been invested into reliable termination methods.

When terminating the membrane to TBM segments, two primary approaches are typically considered: rear-face fixed and cut-face fixed. Each approach has specific design and constructability considerations.

Rear Face Fixed

This method requires additional excavation behind the segment to form a lip for gasket installation. It allows flexibility in positioning TBM gaskets across the segment profile and provides a smoother surface for compression seals. However, it also requires a reliable connection between the membrane termination and the TBM segment gasket system.

Cut Face Fixed

Where conditions allow, this approach enables a more direct connection between the membrane gasket and the TBM lining gasket, reducing the need for additional excavation. It does, however, require precise cutting of segments and thorough surface preparation to achieve an effective seal. As TBM gaskets are often positioned toward the rear of the segment, careful detailing is required to ensure continuity.

Regardless of the method selected, the key requirement remains the same: complete continuity between the membrane system and the TBM gasket. In the water table conditions below, there is no margin for error. Waterproofing must be designed and installed correctly the first time to ensure long-term performance.

Bluey works closely with project teams to develop and implement engineered solutions that address these challenges, supporting reliable waterproofing outcomes in even the most complex tunnel environments.