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. will be constructed using tunnel form. The RCC portion of each 22-story building is planned to be completed in just 4 months using half the set of formworks. The tunnel forms can then be released and made available for Phase 2 of the same project!

Tunnel form technology, like any other new technology, requires attention to various aspects and challenges that differ from conventional construction methods. Some of these challenges include:

• The building's design should accommodate the adoption of tunnel form technology. Hence, the decision to use tunnel form should be made before finalizing the building schematic.
• Involving the tunnel form supplier early on is crucial for optimizing costs. Early involvement ensures the supplier's inputs can be incorporated into the design, and timely delivery of tunnel forms can be assured.
• 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 go and should have the right workability and early strength development.
• Other resources like tower cranes, concrete batching, and rebar handling should match the speed afforded by tunnel form technology.
• Trained manpower should be available as handling tunnel forms involves more mechanical work than carpentry.
• The formwork must be handled and maintained carefully to retain its advantages.
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Despite these challenges, tunnel form technology offers several advantages over conventional beam-column-slab construction, which can help designers, construction managers, and contractors overcome the aforementioned issues. These advantages hold even compared to monolithic slab-wall construction using Aluform (also known as Mivan technology).

Major Advantages of Tunnel Form System

• High seismic resistance due to monolithic slab and wall construction.
• Monolithic structure reduces the number of joints and improves water tightness.
• Reduces labor costs (greater requirement of tower cranes).
• Reduces mobilization costs on-site.
• Reduced construction times (2-3 day slab casting cycles can be achieved), which is up to three times faster than conventional methods.
• Higher quality finishes—fair-faced finish concrete can be achieved.
• No need for plastering.

Adopting tunnel form technology right from the planning and design stages can lead to project cost savings of up to 25%.

Tunnel Form Construction Technique

What is Tunnel Form Construction Technique?

In Tunnel Form Construction Technique, contractors can cast slabs and walls in a short cycle. It combines the quality, speed, and accuracy of off-site/factory production with the economy and flexibility of in-situ construction. Tunnel Form is recognized as a modern method of construction (MMC).

With Tunnel Form technique, we can create cellular reinforced structures with high-quality surfaces that require minimal finishing. The facades and walls can be easily completed with thermally insulated units that can be clad as required. The Tunnel Form technique creates an efficient load-bearing structure suitable for a wide variety of applications.

Applications of Tunnel Form Construction Technique

Tunnel Form Construction Technique is widely used in constructing cellular structures that involve a high degree of repetition, such as:

• Private Housing
• Hotels
• Hostels (Student Accommodation)
• Prisons
• Commercial Complexes
• High Rise Buildings

Benefits of Tunnel Form Construction Technique

• Smooth and fast operation: Due to the use of reinforcing mats/cages and prefabricated forms.
• Enhances quality of construction: Precision of the formwork creates a smooth and high-quality finish.
• Flexibility in design and layout: Large bays can be constructed using tunnel form.
• Ensures higher standards of safety: Edge protection systems, integral working platforms, minimal requirement for tools and equipment, and predictable and repetitive tasks ensure higher safety standards.
• Value for money: Reduces transportation costs, near-zero wastage, just-in-time deliveries, reduced labor requirement, and fast construction leading to lesser cost of financing.
• Environment friendly: No wooden materials are used, and it minimizes heating and air-conditioning requirements compared to conventional buildings.
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Limitations of Tunnel Form Construction Technique

• Tunnel Form is not suitable for small projects or projects involving huge design variations.
• Requires significant initial investment in formwork and other machinery.
• In case of imported formwork, finalization of the plan is required as early as 5 to 6 months.
• Skilled labor is required, unlike traditional systems.
• The building design should be suitable for the system.
• Speedy construction demands high cash flow.
• Special formwork may be needed for specific geometrical forms and angles, leading to additional costs.