What is the tunnel formwork system?
It is a steel half-tunnel system that casts a building's walls and floor slab together in one daily-cycle pour. Two facing half-tunnels form a room-sized cell cast monolithically, then strike and fly to the next bay. It suits repetitive cellular structures like mass housing, hotels and dormitories.
Does plywood form the main face in tunnel formwork?
No. The main wall and soffit are cast against the steel skin of the tunnel units. Plywood does the surrounding work: stop-end and bulkhead forms at bay ends, gable and infill forms for non-repeating geometry, blockouts for openings, and conventional film-faced forms for basements, cores and podiums.
What are the disadvantages of tunnel formwork?
High mobilisation cost that only pays on large repetitive jobs, full dependence on crane time for each fly, the need for a skilled drilled crew to hold the daily cycle, and limited geometry flexibility. Where the plan stops repeating, plywood-faced conventional forms fill the gap.
What plywood spec suits the stop-ends and blockouts on a tunnel-form job?
18 mm film-faced plywood is the baseline. For repeat stop-ends and high-cycle bulkheads use a phenolic EN 636-3 panel (Pro Form, up to 20 reuses); for shorter infill and blockout runs a higher-melamine MUF EN 636-2 panel (Form Extra, up to 15) is the economical choice.
Why do plywood stop-ends fail early on a tunnel-form site?
Usually handling, not a panel defect. Stop-ends are cut and drilled for rebar constantly, so unsealed cuts and holes let in water and cause edge swell. Rough striking damages the corners. Resealing fresh cuts, using a consistent release agent and careful striking keep the forms in service longer.
