Note on tunnel form construction

Tunnel form is a formwork system that allows to cast walls and slabs in one operation on a daily cycle. It combines the speed, quality and accuracy with the flexibility and economy of in-situ construction. Construction durations are reduced significantly by this rapid system when compared to conventional methods. The system creates efficient load-bearing structures which are known as the most earthquake resistant structures. Rohan Builders has adopted the technique at its Rohan Abhilasha project in Wagholi in Pune.

1. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune
TUNNEL FORM CONSTRUCTION TECHNIQUE AT ROHAN
ABHILASHA, PUNE

Contact: Abhishek Bhatewara E: [email protected]


WHAT IS TUNNEL FORM CONSTRUCTION?


Tunnel form is a formwork system that allows the contractor to cast walls and slabs in one operation
on a daily cycle. It combines the speed, quality and accuracy with the flexibility and economy of in-situ
construction. Construction durations are reduced significantly by this rapid system when compared to
conventional methods. Tunnel Form System brings speed, quality and accuracy to concrete construction
and provides big savings in finishing and M&E works. Hi-tech technologies for steel formwork
production make tunnel forms strong & durable. The system creates efficient load-bearing structures
which are known as the most earthquake resistant structures.

The result is a cellular reinforced structure, the surfaces of which are sufficiently high quality to require
only minimal finishing for direct decoration, while the end walls and facades are easily completed with
thermally insulated units that can be clad as required. The system creates an efficient load-bearing
structure for use in a wide variety of applications. It is particularly effective in projects suited to
repetitive cellular construction such as residential blocks, hotels, student accommodation, barracks and
prisons.

2. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune
WHY TUNNEL FORMWORK SYSTEM?

It is economic…

- With one set of formwork, 500 times laying works can be fulfilled in the same project.
- Low cost adaptation to the other similar projects can be provided by adding new formworks and by
repairing the older formworks.
- Since it is managed by a limited number of highly qualified foremen, their assistants and regular
workers, it ensures significant cost saving in labor costs.
- The cost of financing the construction capital is considerably decreased since it speeds up the
construction period compared to the classical systems.

It is fast and reliable…

- It is a formwork system that allows the contractor to lay wall and slab concrete at a time on a daily
basis. Therefore, one layer can be constructed with a set of formwork everyday.
- It can be laid up in the spans required by the project. It can easily be worked in the spans varying
from 1.5 meters to 6.5 meters.
- It is the most reliable system, which is well known to be resistant against earthquakes. Likewise, it is
the most reliable system against severe winds and storms.

It is safe…

- It has integral working platforms and edge protection systems, ensuring considerably successful
results in terms of work safety.
- In addition, the repetitive, predictable nature of the tasks involved encourages familiarity with
operations, and, once training is complete, productivity improves as construction progresses.
- The minimal requirement for tools and equipment when moving the tunnel form further reduces the
risk of accidents on site.
- It is fire resistant.

It provides High Quality…

- It ensures the correct application and the completion of the Project in start-up quality.
- It is possible to build up to 40 storey buildings by laying the wall concrete a little thinner on upper
storey.
- Since the measurement errors are almost non-existant during the production, it provides convenience
in the applications of precast facade wall and panel interior wall.
- Since very smooth concrete surfaces are obtained from the formwork surfaces, wallpaper covering
and painting works are carried out by minimum costs such that there is no need for plastering after
concrete.

It is environmentally friendly…

- It is known to be environmentally friendly as no wooden material is used.
- Heating and air conditioning costs are considerably less compared to the conventional buildings.

3. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune
HOW DOES IT WORK – THE 24-HR CYCLE?

The basic construction sequence is shown in the diagram. In summary, the forms are positioned, steel
reinforcement is fixed and concrete poured and left overnight to cured. The next day when the concrete
has hardened tto around 60%, the tunnelforms are then lowered, removed, the area then backpropped
and the tunnelforms are then positioned for the next days work. This way a team of 20-30 workers can
complete 500m2 +/- of slab and wall construction daily.

4. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune
COMPARISON OF CONVENTIONAL / ALUFORM / TUNNEL FORM

Activity For Conventional For Aluform Shuttering For Tunnel Formwork
Capital Cost Less Cost of shuttering material
is high
Cost of shuttering material
and other related machinery
is very high
Casting System
RCC Frame
structure of beam,
slab, column etc.
casted separately
Monolithic structure of
walls and ceiling casted
together
Monolithic structure of main
walls and ceiling casted
together. Internal portion
walls build after words.
Accuracy and
Quality of
construction
Less Good accuracy but with
proper care Good accuracy
Internal/external
Plastering
required
Required Not required if good
precaution taken.
Not required if good
precaution taken.
Design Changes
Flexibility in design
to incorporate any
changes before
casting
Used for Repetitive
design/mass construction.
Changes in design is
difficult to incorporate.
Used for Repetitive design/
mass construction. Changes
in design is difficult to
incorporate.
Speed of work Slow Moderate to Fast Fast
Cycle time for
RCC work 20 days 10 -15 days
1 days repeat cycle
possible with proper
infrastructure and other
ancillary machineries
No. of repetition
of shutt material 12 to 15 100 to 150 500 +
Advantages Low cost easy to
operate,
High cost but more effective
to operate low manpower,
moderate to fast
construction, with
modification can be used to
other project, most suitable
for high rise and mass
housing.
Long lifespan, low
manpower, speedy
construction, high
reusability, with
modification can be used in
other project with little
different, most suitable for
high rise and mass housing.
Limitations Short lifespan, Slow
speed poor quality
Moderate lifespan &
manpower required,
moderately high speed of
construction, moderately
high investment
High investment, Work only
with tower crane.
Need well experienced
skilled people. Need many
other ancillary machineries
to achieve 1 day repeat cycle
Cost of
shuttering
Around Rs 400 to
500 /sft of shuttering
floor area
Around Rs 5000 to 6000 /sft
of area
(1000 X 5 to 6 times)
Around Rs 9000 to 10000
/sft
(2500 X 3.5 to 4 times)
Extra almost equal cost for
ancillary machineries.
Labour Cost Around Rs. 85 to
100 /sft slab area
Around Rs. 175 to 250 /Sft
slab area
Around Rs. 250 to 300 /sft.
slab area.

5. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune
MACHINERY REQUIREMENT (TO ACHIEVE 24-48HR SLAB CYCLE)

• Tower Crane of 10 ton capacity
• Welded Wire mesh machine
• Concrete Distributor
• Gas heaters (for cold climate)
• Batching Plant
• Hydra
• Other routine machineries



PANEL ASSEMBLY




Panels & its
Assembly

6. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune
LIMITATIONS OF TUNNEL FORM

• Not suitable for small projects, and if there are many variations in design
• High initial investment of formwork and other machineries.
• Imported formwork, need 5 to 6 months early finalization of plan.
• Dependent of formwork supplier for amendments in form work and accessories.
• Wall thickness need to keep 200 mm thick as no offset for column beams possible.
• Need to design building suitable for system.
• Due to speedy construction, high cash flow management required.
• Basement storey cannot be constructed by using tunnel formwork system, removal of formwork
is not possible.
• Various geometrical forms and angles are difficult for which special formwork to be designed,
which will be very expensive
• Due to high production speed management-related functions are vital. Coordination problems
may cause remarkable delays in schedule.
• Skilled labor force is needed compared to traditional systems.

7. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune
CASE STUDY – ROHAN ABHILASHA, PUNE

• Location – Wagholi, Pune
• Plot Area – 30 acres
• No of blocks – 7
• No of Buildings – 25
• LG+G+13
• Total apartments around 2200 nos
• Slab area with tunnel form around 23 lac sft and parking around 7 lac sft
• RCC duration 2 years
• With 2 sets of tunnel form (5000 sqft)

8. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune
ACTUAL CONSTRUCTION

DAY 1 – 1st slab (14th Oct)

DAY 10 – 3rd slab or 6th casting (25th Oct)

9. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune

DAY 20 – 6th slab or 12th casting (6th Nov)

DAY 40 – 10th slab or 20th casting (24th Nov)

10. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune
FINISHING ITEMS

Due to the use of tunnel form construction technique, which is a rapid construction technique, the
finishing items too needed to be completed at the same speed in order to avoid any bottlenecks. The
following technologies have also been used at Rohan Abhilasha to complement the speed ot tunnel
form.

1. PRECAST STAIRCASE


2. TILTING TABLES FOR PRECAST UNITS

11. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune
3. TOILET PODS

12. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune
CONCRETE MIX DESIGN

Design Parameters Details
Grade of concrete M 40
Strength requirement 12-15 Mpa in 12 Hours
De-shuttering period 12 hours according to strength
W/C ratio Minimum 0.27
Slump 180mm after 90 minutes
Accelerators Non – chloride accelerators to be used
Cement 53 grade Max 400 kg/cum
Fly ash Minimum 10 – 15 % (replacement for cement )
Admixture PCE base admixture

Particulars (per cum.) Design for Non-Heating Design for Heating
Cement 380 Kg 330 Kg
Flyash 60 Kg 90 Kg
% replacement 13.63 % 21.42 %
WC Ratio 0.28 0.3
Admixture dose 1% 0.81%
Heating Time ------- 4.5 Hours
Heating Cost ------- 75 to 100 per cum
12 Hours strength 13.5 Mpa 14 Mpa
7 days strength 45 Mpa 34 Mpa
28 days strength 58 Mpa 48 Mpa

Strength Comparison (with admixture)


3.484.225.568.15
22.81
32.61
46.67
8.8912.7416.4425.65
37.6345.78
66.81
0
20
40
60
80
10 Hrs12 Hrs16 Hrs24 hrs3 days7 days28 days
Normal concrete M40HES concrete M40

13. Rohan Builders | www.rohanbuilders.com | P: 020 – 7101 7101 | A: 1 Modibaug, Ganeshkhind Road, Pune

THANK YOU


YouTube Videos:

Timelapse video of Tunnel Form technology at Rohan Abhilasha:
https://www.youtube.com/watch?v=0eE5KHJzHdo

Rohan Abhilasha Project Execution:
https://www.youtube.com/watch?v=yaykCTluGa8

How Tunnel Forwork works (in Animation):
https://www.youtube.com/watch?v=z_CCKgA_o9k







Abhishek Bhatewara
Rohan Builders
W: www.rohanbuilders.com | E: [email protected]