This iconic tunnel has been designed to provide enhanced levels of life safety for the occupants and emergency responders in the event of a major fire whilst protecting this major asset from structural damage. Fast return to service is guaranteed with the addition of thermal linings also minimizing the economic impact if the tunnel were to be closed due to fire.
Project background
a) When the Hong Kong-Zhuhai-Macau fixed link opened, motorists were guided out of western Hong Kong on a 5-km long bridge. From there, an immersed tunnel will take them underwater for a distance of 6.7 km under the Pearl River Estuary before they ascend to a 23-km bridge that takes them to a choice of either Macau or on to Zhuhai in China’s Guangdong province on the mainland. COWI is participating in the design of the immersed tunnel along with CCCC Highway Consultants Co. Ltd. and Shanghai Tunnel Engineering & Rail Transit Design and Research Institute
b) The major considerations for fire protection in tunnels is about safeguarding the tunnel user’s lives and preventing property damage. A tunnel fire in an unprotected tunnel can lead to a major disaster and images of catastrophes in Europe will always remain in our minds. Safeguarding people’s lives means installing and maintaining suitable fire resisting escape paths/cross passages. While this allows tunnel users a safe haven in the event of a fire (or access to the non-incident tube) it also allows the fire brigade and other emergency services to intervene in safe conditions. The potential risk to life in a fire incident in tunnels should be obvious to all.
c) Fire damage to a tunnel can also have enormous financial consequences. Of course, the repair costs are huge, but the effects on the infrastructure are even larger. Tunnels have been out of order for months after a fire. For example, after the fire in the Channel tunnel, the estimated total loss of revenue to Eurotunnel during the period of closure was approximately €200million. Total estimated cost inclusive of the impact on local communities closer to €1 billion.
d) It’s thus critical to protect the world’s tunnels and infrastructure, such as the Hong Kong Zhuhai Macau Bridge tunnel (HZMB). HZMB is considered China’s most important infrastructure project: with 33 immersed structural elements submerged at depths more than 40m below sea water, HZMB also includes numerous long-span suspension bridges and the creation of artificial islands. The 6.7km long tunnel component of HZMB is the world’s longest immersed tunnel for vehicular road traffic. The tunnel will, for example, exceed the length of the current record holder – the Oresund fixed link’s immersed tunnel between Denmark and Sweden – by about 40 per cent. Promat also provided the structural protection on this tunnel.
e) When designing the fire resistance requirements for this tunnel the designers need to evaluate what traffic type and traffic volume were to be using it and based on this research and local standards, the designers chose the RABT curve which simulates a fast-rising very high-temperature fire. This fire curve heats to maximum 1200°C within only 5 minutes (massive thermal shock to the concrete) and stays at 1200 deg C for 2 hrs. It is then subject to a gradual cooling phase of 110 minutes which simulates a real fire – total test time 230 minutes. After the official fire testing, it was determined that 25mm thick PROMATECT®-H was required to be fixed directly to the concrete in accordance with the design and regulatory specifications along with Promat’s installation methods. This fire test was repeated to show the consistency of the result.
Companies involved
- Owner: Project Office of Hong Kong-Zhuhai-Macao Bridge
- Main contractor: China Communications Construction Company Ltd
- Installer: Shenzhen Baoying Construction Group Co, Ltd
- Design: Cowi
- Eternit Guangzhou PROMATECT® H manufacturer (Sister company to Promat)
- Promat China Design, technical and commercial consultants
- Promat Australia PROMASEAL® Fyrestrip manufacturer
- Promat Tunnel Segment Design, technical and commercial consultants
Technical specifications and specific requirements
a) Fire curve is RABT in accordance with the local Chinese standard– maximum temperature of 1200 deg for 2 hrs with a further cooling period of 110 minutes.
b) Board fire protection system is the preferred method of protecting this structure. Spray was not considered by the client.
c) All steel fixings used are 316 grade anticorrosive stainless steel). The designers mandated that these fixings were to have a removable nut that allows for easy removal of the boards if necessary for inspection of concrete if required.
Testing
a) RABT fire curve for boards to protect concrete for 230 minutes. This type of test report issued by the government fire test laboratory (CNCF or NFTC) according to the test standard GB 28376-2012 is a pre-requisite for any qualified bidder for tunnels in China. Failure criteria is reached when the interface temperature exceeds 380 deg C and/or the rebar temperature exceeds 250deg 25mm below the interface.
b) The additional fire test for the concrete slab as mentioned above was required to be carried out as soon as the installation work commenced, the board samples for the test was randomly selected by the owner at the building site. This was for confirmation of performance
c) Expansion joint test. The integrated expansion joint system had been tested by CCCC in the fire test lab of Central South University. The system tested was comprised of 25mm PROMATECT®H (with a steel frame) +25mm ceramic fibre. (50mm was used on the project). The test specimen simulated the designed structure size of the element joint, the maximum temperature limit on watertight rubber is 150deg C.
d) Fixings pull out test. It is imperative that the fixings are tested for pull out strength given the dynamics of the tunnel environment with positive and negative pressures constantly in force. During the installation work, the pulling out force test for fixings was required to be carried out at the site by supervision engineer.
i) For every 10,000 pieces of board, the board sample by random selection was required to be tested in a third-party lab for physical performance as required by standard GB 28376-2012.
ii) For every 20,000 fixings, the fixings (randomly selected) were required to be tested in a third-party testing laboratory for pull out performance and raw material evaluation.
Products:
a) PROMATECT®-H, 25mm thick, approx. 297,000m2
- Direct fixed to concrete linings using stainless steel anchor bolts.
- Also used in conjunction with the major expansion joints
b) PROMASEAL®-A Acrylic Sealant, 600ml foil x 8,000 tubes
- Used for minor expansion/control joints
c) PROMASEAL® Fyrestrip approximately 2,600 lineal meters was installed
- Used as high movement expansion joints.
Construction cost:
RMB 8 billion–over 1 billion Euro (tunnel only)
Elevated working platforms (EWP)
Very early on it was clear that to make installation efficient, elevated working platforms would be required to get to the workface effortlessly. Through consultation with Promat and our experience with many of these types of platforms Baoying designed and manufactured 6 of these EWP. These platforms had adjustable “wings” that could be folded away or lowered, depending on the location of the installation.
Logistics / Installation procedure
The product is shipped by truck from Eternit Guangzhou factory to Zhuhai port facility of CCCC where it is unloaded onto a barge. The barge then makes the 40-km sea journey to the West island where it is unloaded by crane onto trucks on the island. It is then delivered to the designated areas required by Baoying, the installers. Full size boards are trucked to the tunnel at the location of installation. Some boards are taken to the on-site cutting facility where they are fabricated to the on-site requirements – the angled haunches seen in cross section have an angle to be fabricated into the board to minimise gaps. The boards are then lifted onto the elevated working platforms by forklift ready for installation.
The boards are lifted into position using automatic lifters. Once in position, the holes are drilled, bolts are inserted with hammer initially and then tightened using a cordless screw gun to the required torque
Expansion Joints
a) Main expansion strips located at every segment joint, (180 m). This joint was designed between Promat and CCCC and subsequently fire tested. This integrated expansion joint system was tested by CCCC in the fire test lab of Central South University. The system tested comprised of 25mm PROMATECT®H (with a steel frame) +25mm thick ceramic fibre (50mm thick was used in the end). The test specimen simulated the designed structure size of the element joint, the maximum temperature limit on the water resisting rubber seal is 150deg, therefore it was critical to provide the correct protection to limit the temperature exposure to the rubber seals.
b) Minor expansion joint was used within the segment itself @ 22.5m centres and consisted of a 10mm joint filled with Promat flexible, fire resistant sealant.
c) PROMASEAL® Fyrestrip. This was used behind the PROMATECT® H to supplement the fire resistance of the joint as well as to limit air leakage through the joint.
Timing:
Promat started supplying in March 2016 and final shipments for the thermal linings (PROMATECT® H) were complete in late 2017. As per usual on a major infrastructure project such as this, it was critical that the manufacturer kept up production/deliveries with installation requirements for the PROMATECT® H boards and this was done with no delays throughout the duration of the project. The Promat factory in Australia were also required to produce and deliver the PROMASEAL® Fyrestrip in time for installation and this was also finalised in 2017.
Installation rates:
At times, there were up to 60 installing staff on-site and they were achieving very fast installation rates. Total m2 installed per week up to 7,500m2
For more information, go to www.promat-tunnel.com
