The Hong Kong – Zhuhai – Macao Bridge (HZMB), straddled across Lingdingyang of Pearl River Estuary, linking the Hong Kong Special Administrative Region (HKSAR), Zhuhai City of Guangdong Province and Macao Special Administrative Region. The total length is about 42km, counting from the Hong Kong Boundary Crossing Facilities at the east to the Zhuhai/Macao Boundary Crossing Facilities at the west. The uniqueness of the project includes:
Using Large Span Sea Viaduct
The western sea viaduct will be composed of long span bridge sections with main spans in the range of 75-180m. It passes over a navigation channel with a clearance of 41m. Turnaround facility will be provided on this dual 3-lane highway for emergency and operational usages.
Adopting Specific Measures to Minimize Impacts to the Natural Environment
To the east of the sea viaduct section, the HKLR runs into the Airport Channel between the Hong Kong International Airport and the North Lantau. Several measures of the HKLR have been adopted to minimize disturbance to the existing natural environment. These include spanning over the headland between San Shek Wan and Sha Lo Wan of Lantau Island by adopting longer span lengths without physical contact with Lantau Island, minimizing the number of piers of viaduct portion at Sha Lo Wan to reduce visual impact, burying pile caps of the viaduct under the sea bed to minimize disturbance to the existing current flow of Airport Channel and shifting the viaduct to the Airport Island once the airport height restriction allows.
Provision of Landscaping Works for At-Grade Road
This 1.6 km at-grade road will run along the east coast of the Airport Island with provision of extensive landscaping works.
Formation of a Strategic Road Network
As an integral part of the HZMB project, HKLR will be connected effectively to the HZMB Main Bridge, the nearby Hong Kong International Airport, as well as the Tuen Mun and North Lantau area, to form a strategic road network to achieve overall effectiveness and efficiency in land transportation.
Adoption of Tunnel Boring Machines for the Construction of the Sub-sea Tunnel
Construction of the proposed sub-sea tunnel across the Urmston Road between HKBCF and Tuen Mun is proposed to be built by two approximately 14 m diameter Tunnel Boring Machines (TBMs). The use of TBM to form the proposed sub-sea tunnels saves the need of dredging and disposal of some 11 Mm3 of marine sediment that would otherwise be required by traditional immersed tube method.
The adoption of TBM also saves the need to divert several existing power cables now serving the HKIA, minimizes the impact on the busy Urmston Road during construction and the impacts to the marine habitat of the Chinese White Dolphin, within and near the works area of the project. The use of large diameter TBMs of this size to build a sub-sea tunnel in Hong Kong is unprecedented and will be a great challenge to the construction industry in Hong Kong.
The non-dredge reclamation method
Conventionally, seawalls are constructed on firm foundations by replacing the soft marine mud in the seabed by sand fill. This process requires dredging and dumping of a large amount of soft marine mud.
With a view to minimizing the environmental impacts caused by the dredging and dumping for reclamation, Highways Department has developed a non-dredge reclamation for reclaiming the 150 ha artificial island for the HKBCF (including about 20 ha of land for Southern Landfall of Tuen Mun-Chek Lap Kok Link) from the open waters off the northeast of the Hong Kong International Airport. This is the first time this new construction method is used in Hong Kong.
The seawall of the artificial island will be formed by sinking large diameter circular steel cells through the soft marine mud. The steel cells will then be filled up by inert construction & demolition material or sand. The reclamation for the artificial island will also adopt the non-dredge method. This method includes laying of geotextile and 2m thick sand blanket over marine mud prior to reclamation filling. Vertical drains will be installed to accelerate consolidation of marine mud. As such, there will basically be no dredging and disposal of marine mud for the HKBCF reclamation.
The adoption of the above non-dredge reclamation will greatly reduce the amount of dredging and dumping of marine mud by about 22Mm3, and will also reduce the use of about one half of the backfilling material. Furthermore, there will be less impact to the water quality and a large reduction in the construction marine traffic during construction of the reclamation works. This will help to preserve the marine ecology especially the Chinese White Dolphins habitat.
The non-dredge reclamation has lots of benefits over the conventional dredge seawall construction method, including:
(i) Reduce dredging and disposal of marine mud by about 97%;
(ii) Reduce backfilling material by about one half;
(iii) Reduce suspended particles by about 70% and
(iv) Reduce construction marine traffic by about one half.
For more details about the non-dredge reclamation method versus the conventional dredge seawall construction method, please press here.