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Dunne Group LtdTunnel Form2009
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INTRODUCTION
Dunne Building & Civil Engineering Limited operates
within the United Kingdom to fulfil the requirements of
Management and Construction Management Forms of
Contract. It has developed its operational and
management systems to become recognised as a
leading specialist reinforced concrete frame Trade or
Package Contractor. Whilst its core business remains
in the Reinforced Concrete Civils and Structural
market, the Company has expanded its scope of
operations to include other specialist package works
such as Blockwork, Plant Hire and Pre-cast Concrete
and is now actively involved in General Building and
Main Contract works. The flexibility demonstrated by
this successful broadening of its market base has
enabled the Company to maintain its financial strength
in a diminishing and increasingly competitive industry.
The Group’s wholly owned subsidiary, Dunne Plant
Hire Limited also operates from this base, providing a
full plant service to our Construction Projects, including
excavation and earthmoving equipment, mobile
concrete pumps and modular falseworks and
shuttering systems.
Our policy of continued investment in new plant and
construction techniques, together with the proper
management and maintenance of this plant holding, is
essential in providing our clients with a cost effective
product of high quality, whilst not prejudicing our high
safety standards.
Dunne Building & Civil Engineering Limited offers to the
Client and his Professional and Management Team the
experience and expertise to provide the professional,
non-contractual and proactive approach, which will be
essential to the success of this Project.
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Dunne Group LtdTunnel Form2009
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TUNNEL FORM CELLULAR STRUCTURES
GENERAL
Tunnel form is a formwork system that allows
construction of cellular walls and slabs in one
operation on a daily cycle. It combines the speed,
quality and accuracy of offsite production with the
flexibility and economy of in-situ construction and is
recognised as a modern method of construction.
The result is a cellular reinforced concrete structure,
the surfaces of which are of sufficiently high quality to
require only minimal finishing for direct decoration.
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.
Tunnel form is becoming one of the most common
methods of cellular construction as its cost
effectiveness, productivity and quality benefits are
being realised on a wide range of projects throughout
the UK.
Tunnel form is a fast-track method of construction that
is well suited to repetitive cellular projects such as
hotels, social housing and student accommodation.
Recognised as being a modern method of
construction, tunnel form simplifies the whole
construction process by enabling a smooth and fast
operation that can result in frame costs being reduced
by up to 15 percent and provide frame programme
time savings of up to 25 percent.
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Dunne Group LtdTunnel Form2009
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THE 24 HOUR SITE CYCLE
3. LATEMORNINGTunnels arealigned and
reinforcementfixed
5. OVERNIGHT
ThermalCuring
1. STARTConcrete Test toensure previousday’s pour hasreached striking
strength
4. AFTERNOONPreparations
completed andConcrete poured
2. EARLYMORNINGTunnels are
Struck, Cleanedand craned into
next cell
24HOURSITE CYCLE
During the tunnel form construction process, a structural tunnel is created by pouring concrete
into steel formwork to make the floors and walls in one monolithic process. Each 24 hours, the
formwork is moved so that another tunnel can be formed. When a storey has been completed,
the process is repeated on the next floor. A strong, monolithic structure is thus constructed that
can reach 40 or more storeys in height.
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Dunne Group LtdTunnel Form2009
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THE 24 HOUR SITE CYCLE IN PICTURES
1. Start – Concrete Test to ensure previous day’s pour has reached striking strength. The
use of high strength concrete ensures fast construction, typically 15N/mm2 at 14 hours.
2. Early Morning – Tunnels are struck, cleaned and craned into the next cell
3. Late Morning – Tunnels are aligned and reinforcement fixed
4. Afternoon – Preparations completed and concrete poured
5. Overnight – Thermal curing
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TUNNEL CELL DESIGN
Tunnel form creates cells which are 2.4 to 6.6m
wide. The larger cells can be subdivided to create
smaller rooms. Where longer spans are required
up to 11m, the tunnel form can be extended using a
mid span section infill.
Walls can be designed as deep beams and
supported at low level on finished columns to
accommodate under croft car parking.
With tunnel form, the Structural Engineer designs
the one way spanning slabs and walls in
accordance with BS 8100. The innovation is with
the formwork system. Similarly, the Architect must
accept to work with the constraints of regular wall
alignments for tunnel form to be a structural
solution.
The techniques used for tunnel form are already
familiar to Dunne Building and Civil Engineering
Ltd. On average, a team of eight plus a crane driver
can strike and fix 300m2 of formwork each day,
including placing 35m3 of ready mix concrete
(typically 2.5 cells).
The technique provides further inherent benefits of
concrete: high levels of thermal mass, sound
insulation and fire resistance.
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SERVICE RUNS
Service runs can be pre-installed before the concrete is poured
Other facilities such as bathroom pods can be installed as completed units using existing
access platforms
FINISHING
The smooth face of the steel formwork results in
a high quality finish that can be decorated
directly. This reduces the need for finishing
trades thereby providing additional cost savings
and speeding the entire process.
Tunnel form provides a winning combination of
the speed, quality and accuracy of factory
production with the flexibility and economy of in-
situ construction.
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PERCEPTION OF BENEFITS
Flexibility in Design
The large bays constructed using tunnel form, provide exceptional flexibility in the design and
layout of the building and allow a high degree of freedom in the final appearance. The
elevations can be adapted by using extendable formwork to create cantilevered balconies
and the exterior can be finished in any way the architect requires, from brick slips on highly
insulated framed infill panels, to sophisticated curtain walling systems.
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The high levels of dimensional accuracy achieved with tunnel form and the superior load
distribution result in a strong, solid monolithic structure suitable for a multitude of uses. The
ability to create clear spans up to 11m wide provides the opportunity to use non load-bearing
internal partitions that can be moved to provide alternative layouts.
Fast and Economical to Construct
Value engineering starts with the early involvement of the Contractor. In comparison with
traditional R.C. Structures, a general 20 to 25 percent reduction in programme and 10 to 15percent reduction in cost may be realised. The resulting monolithic construction can also
produce savings in the foundations.
Quality
Quality is enhanced despite the speed of construction. The precise, even steel face of the
formwork creates a smooth, high quality finish capable of receiving direct decoration with the
minimum of preparation (a skim coat may be required). This reduces the requirement for
finishing trades, thus providing additional cost savings and speeding the entire process.
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Productivity and Control
The formwork is specially adapted for each project.
The repetitive nature of the system and the use of
prefabricated forms and reinforcing mats/cages
simplifies the whole construction process, producing
a smooth and fast operation. The techniques used
are already familiar to the industry, but with tunnel
form construction there is less reliance on skilled
labour. On average, a team of eight site operatives
plus a crane driver can strike and fix 300m
2
offormwork each day, including placing approximately
35m3 of ready-mixed concrete. The work can
continue in all weather except high winds, and
heaters can be used to accelerate the concrete
curing process.
The schedule provided by the 24-hour cycle means
each operative knows exactly what to do and when,and works to a precisely detailed plan. The smaller
work teams and predictable, measurable daily
production rates simplify and enhance overall
control of the project. Known completion times
make scheduling of material deliveries and follow-on
trades more accurate and optimise cash flow by
facilitating ‘just in time’ principles. By quickly
providing protection, the system allows the follow up
trades to commence work on completed rooms
while work proceeds on upper floors.
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Health and Safety
Tunnel form has integral working platforms and edge protection systems. In addition, the
repetitive, predictable nature of the tasks involved encourages familiarity with operations and
productivity improves as construction progresses. The minimal requirement for tools and
equipment when moving tunnel forms further reduces the risks of accidents on site.
Comprehensive Method Statements and full safety risk assessments enhance safety in tunnel
form’s application. The system meets all current Health and Safety construction site
requirements and for the Client and End User, the superior fire resistance and strength
inherent in the concrete structure increases confidence in the building itself.
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Environment
In today’s environmentally conscious society, we are under ever-increasing pressure to reduce
waste and provide energy efficient buildings within sustainable communities. Tunnel form
provides benefits in key areas:
The in-situ casting of units on site and the local availability of ready-mixed concrete
supplies reduce transportation impacts.
Just-in-time deliveries and near zero wastage produce an overall tidier site withassociated cost savings and safety benefits plus minimum disruption where the site is
already partly occupied.
Concrete’s thermal mass coupled with correct insulation and boiler design minimises
heating costs and can even reduce air-conditioning requirements, with the resultant
benefits for the environment. The monolithic and accurate structure facilitates airtight
construction – an expected requirement in the 2005 amendment to the Building
Regulations, Part L.
Direct finishes and durable walls minimise decoration, repair and refurbishment costs.
Wallpaper can be directly applied or a skim coat may be used to provide a perfect
plastered finish.
In combination with the correct flooring and ceiling systems for separating floors, tunnel
form floors can use the Part E Robust Detail No. E-FC-2 and be confident of passing
the pre-completion testing (PCT) required for Part E sound insulation. With tunnel
form, party walls are simple and can be made of the concrete itself or be non load-
bearing demountable partitions of lightweight concrete block work, or plasterboard
systems. All of these require PCT with a range of suggested options in the Part E
document or from the acoustic specialist, which should satisfy the new requirements.
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Ease of service installation
Service runs can be pre-installed before the concrete is poured. Other facilities such
as bathroom pods can be installed as completed units using existing access
platforms.
Modern Methods of Construction (MMC)
The use of tunnel forms brings factory quality and efficiency to site and so is
recognised as a Modern Method of Construction under the initiative being promoted
by the ODPM. Referenced in Housing Corporation documentation, it is eligible for
use by Housing Associations as a MMC System.
Support
The tunnel form suppliers/contractors provide full design and technical support to
ensure engineers, architects and site staff are all familiar with the system and its
application as the project starts, enabling time and cost savings to be achieved. If the
site staff is inexperienced with tunnel form construction, the supplier’s site training
quickly brings them up to speed.
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Acoustic Test Report
The new tunnel form block of student accommodation at the University of East Anglia was
acoustically tested in August 2004 with excellent results.
Although non domestic residences, university halls, hotels and hostels all have to
comply with the new Building Regulations’ sound requirements of Part E 2003, they will
not be permitted to use the Robust Detail Route and will have to undergo pre-
completion testing (PCT). As a monolithic structure, tunnel form is one of the few
systems that should be totally repeatable and therefore can be used with confidence onfuture projects using the same construction details.
Two separating floors in the new block, consisting of 250mm of concrete with a stuck-
down carpet and no ceiling finish beneath, were tested. They both exceeded the
regulations by more than 5 dB for both airborne and impact sound insulation (actually
meeting the levels required by Robust Details). Had a floating floor and suspended
ceiling been incorporated the results would have been even better.
Two separating walls were also tested, each comprising 180mm concrete with a 2mm
plaster skim finish. Both met the PCT requirement and could have exceeded it further
with the addition of wall linings.
This test, no 040901, carried out by an independent acoustic expert, is downloadable from the
Residential section of The Concrete Centre website at www.concretecentre.com
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Dunne Group Ltd Head Office
Dunne Group Ltd
Head Office: Inchmuir Road, Whitehill Industrial EstateBathgate EH48 2EW
Tel: 01506 657777 Fax: 01506 657770
Regional Office: 4205 Park Approach, Thorpe Park,Leeds LS15 8GB
Tel: 01132 840540 Fax: 01132 840541
Email: [email protected]
Web: www.dunne-group.com
Regional Office: Leigh Commerce Park, Greenfold Way,Leigh, Greater Manchester WN7 3XHTel: 01942 267470 Fax: 01942 267471