Advanced Search

Find company(ies) from Equipment & Products
Find company(ies) from Materials & Services
Find company(ies) from Trade Name
中文 ENG


The Trunk Road T2 and the Cha Kwo Ling(CKL) Tunnel form the middle section of Route 6. They connect the Central Kowloon Route(CKR) to the west and the main tunnel of the Tseung Kwan O –Lam Tin Tunnel (TKO-LTT) to the east. The Route 6 forms part of Hong Kong’s strategic road network and provides an important road link from West Kowloon to Tseung Kwan O (TKO) New Town with intermediate interchanges at Kai Tak and Lam Tin.

Two gigantic tunnel boring machines have commenced tunnel construction works since November 2021. The first tunnel inspection system based on drone and on-board AI processing technologies, “3S Tunnel Defect Inspector", has been successfully applied in the project in 2022. The development of the detection system is the result of the collaborative efforts of Civil Engineering and Development Department and Hong Kong Productivity Council.

Tunnel Boring Machine Launching Shaft

Before tunnelling works could commence, a sizeable tunnel boring machine launching shaft was constructed on the Kai Tak site to install the two tunnel boring machines (TBMs) underground on the tunnel alignment. Owing to its mammoth size, each TBM was split into several parts for hoisting into the shaft and re-assembly. The shaft is 35 m deep (equivalent to 12 storeys underground) and peanut-shaped, distinct from the traditional rectangular shaft.

A peanut-shaped shaft enhances construction flexibility by eliminating strutting. It shortens the time for shaft excavation and TBM assembly by suiting space constraints of the site flexibly. Impacts on adjacent structures and environment can also be reduced.

Launching & Operation of the Tunnel Boring Machines

Two TBMs are deployed to construct the eastbound and the westbound tubes concurrently. The TBMs of this project are equipped with state-of-the-art technologies to cater for different geological conditions, and to fullfil multiple functions–excavation, as well as installing precast tunnel lining and tunnel internal components.

The two TBMs were first completely assembled from parts manufactured in Germany and the Mainland. After detailed factory testing, the TBMs were disassembled into 34 components for shipment to Hong Kong. The heaviest ones weigh up to 480 tonnes each

The TBM components were too sizeable to be delivered by land. Instead, they were shipped directly from the Jiangmen factory to the Kai Tak works site. The 34 components required a total of 10 barge trips.

At the seafront of the Kai Tak works site, a crane barge unloaded the TBM components
onto the shore, from where they were transported by self-propelled modular transporters (SPMTs) to a temporary storage area next to the launching shaft, pending
onward delivery down the shaft by a gantry crane.

After re-assembly in the launching shaft, the two gigantic TBMs have commenced tunnel construction works since November 2021.

3S Tunnel Defect Inspector

The “3S Tunnel Defect Inspector” invented in Trunk Road T2 and Cha Kwo Ling Tunnel project received a Silver Medal in March 2022 in the Geneva International Inventions Exhibition 2022 and recognized as one of the Winners by the 2022 R&D 100 Awards in the Software/Services category in August 2022, it also won the Emerging Technology – Industrial Construction Award in the Hong Kong Business Technology Excellence Awards 2022 in September 2022. The development of the detection system is the result of the collaborative efforts of Civil Engineering and Development Department, Hyder-Meinhardt Joint Venture and Hong Kong Productivity Council. This innovation has been successfully applied in the project.

“3S Tunnel Defect Inspector” is the first tunnel inspection system based on drone and on-board AI processing technologies. Bringing digital upgrade to tunnel inspection, it enables engineers to conduct defect inspections on tunnel linings in a safe and intelligent manner.

Construction quality is particularly important for undersea tunnels which endure huge water pressure and is at risk of sea erosion. In the past, workers had to go on high platforms to examine whether there are concrete cracks, concrete spalling or water leakage in tunnel lining segments – and Cha Kwo Ling Tunnel has 21,000 segments. The old process was dangerous and repetitive. The color and textile of the tunnel surface are monochromatic. Furthermore, most concrete cracks are millimeters in size, which are hard to recognize with the naked eye.

Though there is no internet in the tunnel, the drone can identify segments of the tunnel by scanning QR codes and AprilTag and take high-resoulution images for each compartment that are then sent to the computer. Using a computing technique to analyze the images, the system can also generate a report on the precise location and type of defect.

Source of Information & Pictures: Civil Engineering and Development Department Website

Complimentary copies available to members of the following associations:

The Hong Kong Construction Association
Macau Coustruction Association
Hong Kong General Building Contractors Association
Hong Kong Institute of Utility Specialists
China Hongkong Society for Trenchless Technology Association
Hong Kong Construction Materials Association Limited
Contractor's Authorised Signatory Association
Hong Kong Construction Machinery Association