As part of the mega development of Hong-Kong-Zhuhai-Macau Link, the Tuen Mun-Chek Lap Kok (TMCLK) project involved a 10-km long marine viaduct and several precast segmental bridge approaches linking Lantau Island to the artificial island of Honk-Kong Boundary Crossing Facilities.

  • Name of the owner
    Hong Kong Highways Department
  • General contractor
    Gammon Construction Limited
  • Delivery date
    November 2018
Bespoke solution

The versatile equipment option

To address the client’s constraints, Freyssinet proposed to use both lifting frames and launching gantries.
The advantage of the gantries relied on their capacity to self-propel from piers to piers with no impact on the ground below, while allowing to pick-up and erect segments far away from their destination on the tips of the cantilevers being erected. The ability to bring precast segments with minimum interference to traffic was one of the key aspects of the project since highways and MTR were the main accesses to the city of Tuen Mun and to the International Airport of Hong-Kong.

Therefore, two 1,000-ton steel gantries measuring 200 meters each were specially designed to allow erection using the cantilever and the span-by-span methods, which was most appropriate to build the viaduct’s end-spans. The gantries could erect segments up to 120 tons and span length up to 123 meters.

Lifting frames were designed to erect segments up to 180 tons and span length up to 200 meters.

 

  • 2,652
    Total number of precast segments
  • 6,600t
    PT material fabricated, supplied, installed, stressed, and grouted (Tons)
  • 900t
    Heaviest end-span to be carried by the gantry (Tons)
  • 80m
    Longest cantilever span reached by the gantry during launching (meters)
  • 320
    Freyssinet Team at peak

Operational excellence

Although complex to assemble, the gantry is a powerful piece of machinery which can erect a pair of segments in few hours. The equipment being fully autonomous, the segment erection cycle could be split in short periods adapted to the short traffic closure granted by Highways and MTR.

Segments were secured by post-tensioning bars

We had to erect and secure segments above carriageways in a time frame of 3 hours. Segments were secured by post-tensioning bars, prior to installing cantilever PT tendons ensuring a fully safe and controlled process compatible with the high safety expectation of Highways and MTR authority for works being carried out above traffic.

TMCLK link - balanced cantilever erection with launching gantry and post-tensioning bars
TMCLK link - deck geometry control - launching gantry

Deck geometry control

During the balanced cantilever erection, the supports of the gantry are located on the piers. The cantilevers are not affected by significant temporary work loads, which eases the ability to predict and correct the deck geometry.

Customized formworks fully handled by the gantry winch trolleys were used to close the gap between two consecutives cantilevers.

Bespoke hydraulic adjustment device spanning to consecutive cantilever tips was used to fine-tune and lock the alignment before concreting.

Intensive assembly works using post-tensioning bars

The match-cast faces of the segments were glued with epoxy and then post-tensioned with post-tensioning bars to the previous one using concrete blisters cast on every segments.

At each erected pair of segments, cantilever tendons going through the deck top slab from one tip to the other were stressed.

When two consecutive cantilever spans were completed, they were linked together at midspan by a concrete stitch. Then continuity tendons going through the bottom slab were stressed.

Eventually, once the viaduct’s end-spans were fully connected, the external post-tensioning could be installed. These external tendons crossing the full viaduct length inside the segment boxes would give the final strength to the viaduct.

13C15 and 19C15 units have been used for internal PT and 31C15 unit for External PT.

TMCLK link - post-tensioning bars
TMCLK link - balanced cantilever erection with launching gantry

A logistics challenge

Thousands of segments had to be erected and tons of post-tensioning tendons had to be stressed on several viaducts using different methodologies and equipment. Each methodology was specific and required expert teams to handle it. We had up to 11 erection work fronts active days and nights to tackle production target and logistic constraints. Each segment had to be specifically prepared to its destination (collective protection installation, spreader beams connections, temporary PT bars, etc.).

Freyssibars diameter 40 mm and 50 mm have been used to perform all temporary PT.

Every team activity was crucial and therefore operated through a stringent process allowing traceability and full quality control.

We knew we undertook to build a challenging job by its size and complexity; but it is only when it takes a full day to visit each of the 11 working fronts that you realize its real size and the importance of the logistics on a viaduct that crosses a major highway, Airport Express Rail together with a sizable marine part!

Michel  
Former managing Director, Freyssinet Hong-Kong

A full range of expert skills

To match the productivity required by the project, specialized Freyssinet teams were engaged to cover all scopes involved in such construction:

  • launching gantry team in charge of the equipment operation and erecting segments
  • lifting frame team in charge of the equipment operation and erecting segments
  • stitch team in charge of assembling formworks and perform the concreting
  • Post-tensioning (PT) team in charge of the continuity PT, external PT and overall grouting operations

Another team was also created to support the main contractor in pier head segment erection. The positioning of the pier head segment was crucial for the future cantilever geometry and must be done to the millimeter. It was achieved with hydraulics on sliding boxes allowing to adjust the pierhead segments in 3 dimensions. The team ultimately completed the process of viaduct erection by installing and grouting the bearings on end-span piers once the external PT had been done.

TMCLK team
Erecting a total of 2,652 segments to build the viaducts
Supplying several sets of lifting frames
Purposely designing two versatile launching gantries for the project
Preparing pier head segments and pre-installing Freyssinet pot bearings
Complex viaduct erection sequence to cope with segment delivery constraints
Tackling the curve above the railways
Crossing carriageways
Installing the last Lantau side segments

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