Tunnel Form Technology

GEM has been appointed as a project manager by one of the reputed developers in India, at their project in Pune wherein tunnel formwork system is being used. This is our first experience with the Tunnel form technology. The project has a built-up area of 13.83 lakhs sq.ft. in (Phase 1) out of which about 10 lakhs sq.ft. built-up area will be made using tunnel form. RCC part of each of the 22 story buildings is planned to be completed in just 4 months with half set of formworks. The tunnel forms can thus be released and be available for Phase 2 of the same project!
Tunnel form technology like any other new technology requires attention to many aspects and challenges of construction in a different manner than in conventional works. Some of these challenges may be:

• The planning of the building should lend itself to the adoption of tunnel form technology. That is why the decision to use tunnel form should be taken even before the schematic of the building is finalized.
• Similarly, the tunnel form supplier should also be on board from an early stage so that their inputs to optimize cost of tunnel form can be incorporated in design if possible. In time delivery of tunnel forms can also be assured by having the vendor on board early.
• The number of flats (repetition) should be large enough to justify the higher capex on tunnel form.
• The concrete mix should be carefully designed to allow pouring all concrete in one pour and should have the right workability and early strength development.
• Other resources like tower crane, concrete batching and rebar handling and placement should match the speed afforded by tunnel form
• Trained manpower should be available to handle the tunnel form as it has more to do with assembly (mechanical work) than carpentry!
• The form work must be handled and maintained carefully else many of the advantages will evaporate.

At the same time, Tunnel form technology offers many advantages over conventional beam-column-slab construction which may overcome above mentioned challenges faced by designers, construction managers and contractors. Many of these advantages hold good even when it is compared with monolithic slab-wall type of construction using Aluform (popularly known as Mivan technology).
Major Advantages of Tunnel Form System:

• High seismic resistance due to monolithic slab & walls construction
• Monolithic structure reduces number of joints and improves water tightness
• Reduce labour costs (greater requirement of tower crane)
• Reduce mobilization costs on site
• Reduced construction times (2-3 days slab casting cycle can be achieved) which is up to 3 times faster than conventional
• Higher quality finishes –Fair faced finish concrete can be achieved
• No need for plastering

If the technology is adopted right from the planning and design stage, project costs savings up to 25% can be achieved.