Construction overview
Overview of the project's construction. Video: Compilation of EIA videos.
Construction Methods
VIADUCT
Hong Kong LR Viaduct
The Hong Kong LR viaduct will join the limits of the Hong Kong Special Administrative Region to Hong Kong International Airport Island. The substructure of the viaduct will be built mainly in the marine environment. The substructure construction will be made of reinforced columns on marine bored piles and surrounded by casings to protect the marine environment against spills or leaks.
Hong Kong LR Viaduct
The Hong Kong LR viaduct will join the limits of the Hong Kong Special Administrative Region to Hong Kong International Airport Island. The substructure of the viaduct will be built mainly in the marine environment. The substructure construction will be made of reinforced columns on marine bored piles and surrounded by casings to protect the marine environment against spills or leaks.
Dredging of sea sediments for the building of marine bored pile.
Note the oversized casing that prevent spills and leaks. Photo: EIA
Note the oversized casing that prevent spills and leaks. Photo: EIA
HKLR viaduct. Photo: Screenshot of Project video
The superstructure of the viaduct will be made of a dual-3 lane with hard shoulders for each bound. The method for the construction of the spans was not determined in the EIA but three different methods were recomended for the contractor to chose from. The first method is the precast segmental method, which consists in lifting onto place premade segments of less than 80 metres long. The second method is the precast spans method, which consists in lifting onto place premade segments similarly to the first method. However, the precast spans method require vessels of mega lifting capacity to lift onto place segments of more than 100 meters long. The third method is the In-situ balanced-cantilever method. The former method consists in constructing on place the different segments of the viaduct and to pre-stress them onto the previous segments. For navigation purpose, the viaduct requires having some spans longer than 75 meters. Therefore, if the contractor chose to use the first construction method, the precast segmental method, he would also have to use either of the second or third construction method as well.
Short clip on construction of the viaduct using the precast segmental method. Video: Compilation of EIA videos.
TUNNELS
Hong Kong LR Tunnel
At the eastern end of the Hong Kong LR viaduct, the road will become a tunnel that will link the Hong Kong International Airport Island to the Hong Kong BCF. The first portion of the tunnel requires going through the rock formation of Scenic Hill. For this section the tunnel would be mined with a tunnel-boring machine and absolutely no blasting would be used. Blasting vibration could affect the nearby car-cable facility and the airport railway. Beyond the Scenic Hill, the tunnel would be constructed with a combination of the cut-and-cover method and the trenchless method. The cut-and-cover method involves the excavation of a trench and the in-situ construction of the tunnel structure. The trench is then refilled around and on top of the tunnel. The trenchless method, as its name implies, is the excavation of the tunnel without the formation of a trench. The trenchless method would be used in case where open cut in the ground is not permitted like for the portion where the tunnel has to pass under the airport railway.
A second tunnel will link one portion of the Hong Kong BCF and the airport island. This tunnel will be built in the Hong Kong LR Tunnel reclamation area (see below) by the cut-and-cover method and the trenchless method.
Hong Kong LR Tunnel
At the eastern end of the Hong Kong LR viaduct, the road will become a tunnel that will link the Hong Kong International Airport Island to the Hong Kong BCF. The first portion of the tunnel requires going through the rock formation of Scenic Hill. For this section the tunnel would be mined with a tunnel-boring machine and absolutely no blasting would be used. Blasting vibration could affect the nearby car-cable facility and the airport railway. Beyond the Scenic Hill, the tunnel would be constructed with a combination of the cut-and-cover method and the trenchless method. The cut-and-cover method involves the excavation of a trench and the in-situ construction of the tunnel structure. The trench is then refilled around and on top of the tunnel. The trenchless method, as its name implies, is the excavation of the tunnel without the formation of a trench. The trenchless method would be used in case where open cut in the ground is not permitted like for the portion where the tunnel has to pass under the airport railway.
A second tunnel will link one portion of the Hong Kong BCF and the airport island. This tunnel will be built in the Hong Kong LR Tunnel reclamation area (see below) by the cut-and-cover method and the trenchless method.
HKLR Tunnel link the viaduct to the Hong Kong BCF. Photo: Screenshot of Project video
Automated People Mover Photo: http://www.checkerboardhill.com
Automated People Mover (APM)
An APM will transport travellers from the Hong Kong BCF to the Hong Kong International Airport Island via a tunnel. The tunnel will be constructed with the cut-and-cover method and mining method similar to the Hong Kong LR tunnel. However, for the marine portion of the tunnel, the immersed tube method will be used. The immersed tube method consists in the immersion of several premade tunnel units that are then assembled with the underground portions of the tunnel.
An APM will transport travellers from the Hong Kong BCF to the Hong Kong International Airport Island via a tunnel. The tunnel will be constructed with the cut-and-cover method and mining method similar to the Hong Kong LR tunnel. However, for the marine portion of the tunnel, the immersed tube method will be used. The immersed tube method consists in the immersion of several premade tunnel units that are then assembled with the underground portions of the tunnel.
RECLAMATION WORK
Hong Kong LR Tunnel Reclamation Work
In order to protect the eastern part of the Hong Kong LR tunnel from ship impact some reclamation work have to be done. The first part of this reclamation work is the creation of a seawall around the designated area. The seawall will be built on a dredged sea surface and the structure would consist of a rock filling with small rocks and rock armouring with large-sized rocks. The reclamation filling between the seawall and the airport island would involve the layering of geotextile and sand blankets on to of a non-dredged sea surface. Consolidation measures, such as vertical band-drains, would be installed across the geotextile and sand blankets in order to solidify the reclamation work. In the eventuality where the dredged marine deposits are contaminated with chemicals and heavy metals, the deposits would be put back into the trenches during reclamation work.
Hong Kong BCF
Similar to the Hong Kong LR Tunnel Reclamation Work, the Hong Kong BCF reclamation work would start first with the construction of a similar seawall. The seawall will prevent significant sediment spread during the filling of the area. The EIA assumed that the seawall would also be built on a completely dredge sea surface although a contractor could choose to not do so. The EIA recommends the construction of a sloping BCF seawall because it is the most effective design to absorb wave impact. Moreover, vertical seawalls are usually adopted if vessels are needed to berth, which is not the case in this project. As for the reclamation area itself, it is the contractor, the time constrains and the environmental samplings that would determine if the reclamation area will be fully, partially or not dredged. The EIA recommends to not dredge the reclamation area as it would be more ecological but it also admit that it is time consuming to consolidate reclamation work on a non-dredged surface. Whether or not the reclamation base will be dredged, the reclamation filling would consist of the same technique (geotextile and sandblankets) as for the Hong Kong LR Tunnel Reclamation Work.
If the dredge sediments have a Type 2 or 1 level of contamination, the sediments would be put back into the reclamation area or seawall trench. If the dredge sediments have a Type 3 level of contamination (highly contaminated with pollutents), they will be placed into the Hong Kong contaminated mud pit to prevent their spread and into the marine environment.
Hong Kong LR Tunnel Reclamation Work
In order to protect the eastern part of the Hong Kong LR tunnel from ship impact some reclamation work have to be done. The first part of this reclamation work is the creation of a seawall around the designated area. The seawall will be built on a dredged sea surface and the structure would consist of a rock filling with small rocks and rock armouring with large-sized rocks. The reclamation filling between the seawall and the airport island would involve the layering of geotextile and sand blankets on to of a non-dredged sea surface. Consolidation measures, such as vertical band-drains, would be installed across the geotextile and sand blankets in order to solidify the reclamation work. In the eventuality where the dredged marine deposits are contaminated with chemicals and heavy metals, the deposits would be put back into the trenches during reclamation work.
Hong Kong BCF
Similar to the Hong Kong LR Tunnel Reclamation Work, the Hong Kong BCF reclamation work would start first with the construction of a similar seawall. The seawall will prevent significant sediment spread during the filling of the area. The EIA assumed that the seawall would also be built on a completely dredge sea surface although a contractor could choose to not do so. The EIA recommends the construction of a sloping BCF seawall because it is the most effective design to absorb wave impact. Moreover, vertical seawalls are usually adopted if vessels are needed to berth, which is not the case in this project. As for the reclamation area itself, it is the contractor, the time constrains and the environmental samplings that would determine if the reclamation area will be fully, partially or not dredged. The EIA recommends to not dredge the reclamation area as it would be more ecological but it also admit that it is time consuming to consolidate reclamation work on a non-dredged surface. Whether or not the reclamation base will be dredged, the reclamation filling would consist of the same technique (geotextile and sandblankets) as for the Hong Kong LR Tunnel Reclamation Work.
If the dredge sediments have a Type 2 or 1 level of contamination, the sediments would be put back into the reclamation area or seawall trench. If the dredge sediments have a Type 3 level of contamination (highly contaminated with pollutents), they will be placed into the Hong Kong contaminated mud pit to prevent their spread and into the marine environment.
Hong Kong BCF seawall and reclamation work in action. Video: Compilation of EIA videos.
Hong Kong BCF overview. Photo: Screenshot from Project video
ROADWORD AND BUILDING CONSTRUCTION
Hong Kong BCF Roadwork
At-grade roads on the reclamation area will be built on a sub-base material and toped by bituminous surfacing. Several elevated bridge structures will be built to overpass the different projects (tunnels, road and bridges) linking Lantau to the Hong Kong International Airport. The bridges will be built with reinforced concrete structures and would either be constructed in-situ or from precast since both techniques have similar environmental impact according to the EIA.
Buildings within Hong Kong BCF
The buildings that will be constructed on the BCF are the Passenger clearance building (PCB) and several buildings to accommodate Government departments, personnel and accommodate travellers. The PCB would measure 160 meters by 200 meters with four storeys. The material used in its construction would consist of in-situ reinforced concrete, precast concrete constructions and prefabricated steelwork pieces. As for the other buildings, there are no specific indication in the EIA on how the buildings should be constructed, but the EIA do specify that their structural form should not affect the sensitive receivers. The guidelines for environmental impact should also be followed during and after the buildings construction.
Hong Kong BCF Roadwork
At-grade roads on the reclamation area will be built on a sub-base material and toped by bituminous surfacing. Several elevated bridge structures will be built to overpass the different projects (tunnels, road and bridges) linking Lantau to the Hong Kong International Airport. The bridges will be built with reinforced concrete structures and would either be constructed in-situ or from precast since both techniques have similar environmental impact according to the EIA.
Buildings within Hong Kong BCF
The buildings that will be constructed on the BCF are the Passenger clearance building (PCB) and several buildings to accommodate Government departments, personnel and accommodate travellers. The PCB would measure 160 meters by 200 meters with four storeys. The material used in its construction would consist of in-situ reinforced concrete, precast concrete constructions and prefabricated steelwork pieces. As for the other buildings, there are no specific indication in the EIA on how the buildings should be constructed, but the EIA do specify that their structural form should not affect the sensitive receivers. The guidelines for environmental impact should also be followed during and after the buildings construction.
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