SEM Tunnel Injectable Tubing Injections — Highway 407 & Jane Street

The problem. A sequential excavation method (SEM) tunnel at Highway 407 and Jane Street had injectable tubing cast into its concrete cold joints — the pre-installed hoses that allow joints to be sealed by injection after the pour. Injectable tubing is often called “the forgotten bid item”: it only works if someone proves each tube is clear and then injects it properly, joint by joint.

The repair. Working to a written, repeatable procedure, the crew proved each tube first — injecting clean water from end A until it exited end B (or re-injecting from B where flow was blocked), then crimping off and pressurizing to approximately 500 psi to observe whether water leaked through the cold joint. After purging each tube with compressed air, polyurethane resin was injected the same way — limited to 2–5% accelerator, pumped to approximately 1,000 psi or a maximum of 40 litres of resin per 7-metre tube length, whichever came first.

The result. Every accessible cold joint was water-tested, purged, and resin-injected under a documented pressure-and-volume procedure, converting a commonly neglected bid item into a verified, sealed tunnel lining. The written methodology from this project is one we still work to on segmental and SEM tunnel joints.

Project photos