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Geotechnical works of the Hong Kong-Zhuhai-Macao Bridge Project
Albert T. Yeung i)
i) Associate Professor, Department of Civil Engineering, University of Hong Kong, Pokfulam, Hong Kong
ABSTRACT
The Hong Kong-Zhuhai-Bridge Project, being situated in the waters of Lingdingyang (伶仃洋) of the Pearl River
Estuary, is a mega sea-crossing infrastructure project currently under construction in the Pearl River Delta of China.
It consists of a series of bridges, sub-sea tunnels, viaducts and artificial islands connecting the Hong Kong Special
Administrative Region ("Hong Kong") (香港), Zhuhai City of Guangdong Province ("Zhuhai") (珠海), and the
Macao Special Administrative Region ("Macao") (澳門), three major cities situated on the Pearl River Delta of China.
The functions of the Project are: (1) to meet the demand of passenger and cargo interflows among Hong Kong,
Mainland China (particularly the western Pearl River Delta region) and Macao; (2) to establish a new land transport
link between the east and west banks of Pearl River; and (3) to enhance the economic and sustainable development
of the three major cities in the Pearl River Delta region. The geotechnical works associated with the Project,
including reclamations, onshore and offshore foundations, sub-sea tunnels, artificial islands, earth retaining
structures and roadworks are extensive, large-scale, diversified, challenging and complex. In this special lecture, the
background of the mega project and pertinent geotechnical works of the Project, in particular components
contributed by the Hong Kong Special Administrative Region Government ("HKSARG"), are described. Moreover,
green measures implemented to reduce environmental impacts during the design and construction stages of the
Project are also presented.
Keywords: Hong Kong-Zhuhai-Macao Bridge; geotechnical works; foundation, sub-sea tunnel; artificial island;
reclamation; green measures; immersed tube tunnel, Chinese White Dolphin
1 INTRODUCTION
The Hong Kong-Zhuhai-Macao Bridge ("HZMB")
Project is a mega sea-crossing infrastructure project
currently under construction in the Pearl River Delta
("PRD") of China. It consists of a series of bridges,
sub-sea tunnels, viaducts and artificial islands
connecting the Hong Kong Special Administrative
Region (香港特別行政區) ("Hong Kong") (香港),
Zhuhai City of Guangdong Province of Mainland China
(廣東省珠海市) ("Zhuhai") (珠海), and the Macao
Special Administrative Region ( 澳門特別行政區)
("Macao") (澳門), three major cities in the PRD region
of China.
The HZMB Project is expected to cost more than
US$10.6 billion. However, it will benefit the economic
development of the PRD region significantly. By
linking up Hong Kong, Zhuhai and Macao, the
completed HZMB Project will form a systematic
regional transport network by providing an overland
vehicular link. The link will substantially shorten the
travel time between the eastern and western PRD
region, so as to increase the interflows of passengers,
cargoes and even capital within the region. Upon
completion of the HZMB Project, the western PRD
region will be within a 3-hour-commuting radius from
Hong Kong, resulting in substantial reduction in both
transportation cost and time, whilst the cargo and
passenger flows from the western PRD region,
Guangdong (廣東省) and Guangxi (廣西省) Provinces,
Mainland China will be able to utilize the transportation
facilities of the Hong Kong International Airport
("HKIA") and the Kwai Chung Container Ports in
Hong Kong. The HZMB will thus help to facilitate
closer economic integrations between Hong Kong and
the PRD region, so as to enhance the economic
competitiveness of the region. Moreover,
environmental impacts induced by vehicular traffic will
be significantly reduced.
The link will also help to realize the strategic
benefits of promoting the socio-economic development
of the western PRD region. With closer economic tie
with her neighboring region, Hong Kong can assume a
leading role in driving the economic development in
South China. It will also enable Hong Kong to continue
as an international aviation and shipping center in the
region. The connectivity of the HZMB to other major
cities in the western PRD region is depicted in Fig. 1.
The 15th Asian Regional Conference on
Soil Mechanics and Geotechnical Engineering
Japanese Geotechnical Society Special Publication
109http://doi.org/10.3208/jgssp.ESD-KL-3
Fig. 1. Connectivity of the HZMB to other major cities in the
western PRD region
The geotechnical works associated with the Project,
including reclamations, onshore and offshore
foundations, sub-sea tunnels, artificial islands, earth
retaining structures and roadworks, are extensive,
large-scale, diversified, challenging and complex. The
preservation of the Chinese White Dolphin habitats in
nearby waters also poses tremendous environmental
challenges to the Project. In this special lecture, the
background of the mega project and pertinent
geotechnical works of the Project, in particular
components contributed by the Hong Kong Special
Administrative Region Government ("HKSARG"), are
described. Moreover, green measures implemented to
reduce environmental impacts during the design and
construction stage of the Project are also presented.
2 BACKGROUND OF THE PROJECT
Significant developments of vehicular transportation
links from Hong Kong and Macao to the eastern PRD
region of Guangdong province, Mainland China have
been accomplished since the 1980s. However, the
transportation links between Hong Kong and the
western PRD region are underdeveloped. Other than the
speedy hydrofoil service to Macao, the vehicular
transportation link from Hong Kong to the western
PRD region, denoted by the pink route in Fig. 1, is
indirect, tortuous and lengthy. It is approximately
200 km long and requires approximately 4 hours of
travel time. As a result, it is insufficient to meet the
transportation needs of the region.
After the 1997 Asian Financial Crisis, the HKSARG
considered that it was necessary to exploit the
advantages of Hong Kong and Macao to revitalize the
depressed economy and to seek new avenues for
economic growth. As a result, the HKSARG proposed
the construction of the HZMB, a vehicular sea-crossing
linking Hong Kong, Zhuhai and Macao, to the Central
Government of China in 2002. As shown in Fig. 1, the
proposed HZMB is approximately 40 km long and it
requires only approximately 45 minutes of travel time
from Hong Kong to the western PRD region.
Research jointly sponsored by the National
Development and Reform Commission (國家發改委)
and the HKSARG on Transport Links between Hong
Kong and the West Bank of the Pearl River
《香港與珠江
西岸交通聯係研究》was completed in July 2003. The
results of the research indicate that the bridge
connecting the three major cities in the PRD is of great
political and economic importance, and should be
constructed as soon as possible.
On 4th August, 2003, the State Council of China (中
國國務院) approved the commencement of preliminary
work for the HZMB Project, and established the HZMB
Advanced Work Coordination Group ("AWCG") (港珠
澳大橋前期工作協調小組). The Group is composed of
government representatives of Guangdong Province,
Hong Kong and Macao, with HKSARG as the
convener.
On 23rd February, 2004, the HZMB AWCG
officially signed a Memorandum commissioning CCCC
Highway Consultants Co., Ltd. to conduct the
feasibility study for the HZMB Project. The
Administrative Office of the HZMB AWCG was
established in March 2004, indicating full-scale
implementation of the preliminary work of the HZMB
Project.
The Feasibility Study Report of Hong Kong-Zhuhai-
Macao Bridge Project (To be Approved)《港珠澳大橋工
程可行性研究报告 (送審稿)》was formally submitted to
the HZMB AWCG on 5th December, 2004, proposing
three main categories of alternatives, i.e. the San Shek
Wan (散石灣) northern alignments, the San Shek Wan
southern alignments and the Extreme southern
alignment, with a total of six alignment options.
The South China Sea Fisheries Research Institute
was commissioned by the HZMB AWCG in March
2005 to conduct the thematic study of the influences of
the Bridge on the Indo-Pacific humpback dolphin
(Sousa chinensis) or commonly known as the Chinese
White Dolphin.
On 2nd April, 2005, it was agreed by the
representatives of the three regional governments to
adopt: (1) San Shek Wan, Lantau in Hong Kong as the
east landing point of the HZMB; (2) Gongbei (拱北),
Zhuhai/Macao as the west landing point of the HZMB;
and (3) the bridge-cum-tunnel solution of the north line
from San Shek Wan to Gongbei/Macao.
On 27th December, 2006, the State Council
approved the establishment of a Special Task Force for
the HZMB (港珠澳大橋專責小組), led by the National
Development and Reform Commission, to be in charge
of the coordination of important and critical issues to
expedite the progress of the HZMB Project. The
HZMB Special Task Force was thus established in
January 2007. Shortly afterward, the Special Task
Force specified that the boundary crossing facilities of
each regional government should be set up within their
own respective territories, and the port setting and
110
inspection of the HZMB should follow the principle of
"three regions, three custom inspections" (三地三檢).
The three regional governments agreed on the
financial responsibility of the construction of the
HZMB Main Bridge-cum-Tunnel on 27th November,
2008. The cost of the Main Bridge-cum-Tunnel will be
shared according to an agreed principle of Equalization
of Benefit to Cost Ratio where Hong Kong, Guangdong
Province and Macao will bear 50.2%, 35.1% and 14.7%
of the construction cost, respectively. The three
regional governments would also be responsible for the
construction of the boundary crossing facilities, ports
and connecting links within their territories
individually.
The Feasibility Study Report of Hong
Kong-Zhuhai-Macao Bridge Project was officially
approved by Premier Wen Jiabao at an executive
meeting of the State Council on 28th October, 2009,
marking the completion of the preliminary work of the
HZMB Project and the official implementation of the
Project.
Various design and construction contracts were
signed by the Hong Kong-Zhuhai-Macao Bridge
Authority (港珠澳大橋管理局) afterwards for the
HZMB Main Bridge-cum-Tunnel. On 15th December,
2009, the construction commencement ceremony of the
HZMB Project was held in Zhuhai, marking the
beginning of the construction phase of the Project.
3 THE HZMB PROJECT
The HZMB Project is composed of three major
components as shown in Fig. 2: (1) the Zhuhai Link
Road ("ZHLR") and the Zhuhai/Macao Boundary
Crossing Facilities ("ZMBCF"); (2) the Main
Bridge-cum-Tunnel structure; and (3) the Hong Kong
Link Road ("HKLR") and the Hong Kong Boundary
Crossing Facilities ("HKBCF"). Details of the three
components are as follows:
1) The Zhuhai/Macao Boundary Crossing Facilities are
located on an artificial island in Guangdong waters
off Gongbei, Zhuhai of area of approximately
209 ha. The Zhuhai Link Road starts from the
artificial island, passes through the developed area
of Gongbei via a tunnel towards Zhuhai, and
connects the Guang-Zhu West Expressway (廣珠西
線) under planning as shown in Fig. 2.
2) The Main Bridge runs from the artificial island off
Gongbei of Zhuhai to West Artificial Island from
where it is connected by an immersed tube tunnel to
East Artificial Island which is located immediately
west of the Guangdong/Hong Kong boundary as
shown in Fig. 2. The bridge-cum-tunnel structure
accommodates a 29.6-km long dual 3-lane
carriageway. The 22.9-km long Bridge includes
three cable-stayed spans between 280 m and 460 m
and the sub-sea Tunnel is approximately 6.7 km
Fig. 2. Overview of the Hong Kong-Zhuhai-Macao Bridge Project
111
long, connecting West Artificial Island and East
Artificial Island.
3) The Hong Kong Link Road ("HKLR") connects the
Main Bridge-cum-Tunnel from East Artificial Island
to the Hong Kong Boundary Crossing Facilities
("HKBCF") as shown in Fig. 2. It is a dual 3-lane
carriageway approximately 12 km long, and
includes sections of sea viaduct, tunnel and at-grade
road along the east coast of Airport Island. The
HKBCF is located on an artificial island in Hong
Kong waters off the northeast of the HKIA,
connecting to Zhuhai and Macao via the HKLR and
the Main Bridge-cum-Tunnel. It also connects to the
HKIA as well as northwest New Territories and
north Lantau of Hong Kong via the Tuen Mun-Chek
Lap Kok Link ("TM-CLKL"). The Tuen Mun
Western Bypass ("TMWB") is a 4.8-km long dual
2-lane highway connecting the TM-CLKL in the
south and Tsing Tin Road in the north where it will
connect to the Hong Kong-Shenzhen Western
Corridor. The reclamation for the artificial island
accommodating the HKBCF is approximately
150 ha in area including approximately 20 ha for the
Southern Landfall for the sub-sea tunnel of the
TM-CLKL.
It has been mutually agreed that the Main
Bridge-cum-Tunnel within Guangdong territory (from
the Guangdong/Hong Kong boundary to the artificial
island accommodating the ZMBCF) will be built jointly
by the three regional governments. The remaining
section in Hong Kong territory (from San Shek Wan in
Lantau, Hong Kong to the Guangdong/Hong Kong
boundary) will be built by the HKSARG. The BCFs of
the three regions and their link roads will be built and
administered independently by each jurisdiction.
4 GEOLOGY OF THE REGION
Pearl River is discharging southwards through its
estuary between Hong Kong and Macao into South
China Sea. It is the only major source of sediments for
this region other than local erosion products washed
down into the sea during heavy summer rains.
The eastern and central waters of Hong Kong are
protected from Pearl River by Lantau Island and no
significant amounts of sediment are carried into these
waters. However, thick deposits of soft marine deposits
do occur, but their source is essentially clay, silt and
sand derived from the erosion of decomposed granite
and decomposed rhyolite. The Hong Kong waters are
thus always clear, except close to shore after rains, and
no dredging of navigational channels has ever been
required.
In contrast, the western coast of Hong Kong is
exposed to the influence of Pearl River, and so is
Macao. Very thick deposits of soft marine deposits are
found offshore; the waters are turbid for most times of
the year, and continual dredging of navigation channels
in Macau has always been necessary.
Lumb (1977) concluded from his investigation on
the soft marine deposits of Hong Kong and Macao that
the source of material is not significant and the locally
derived soils behave in the same manner as the Pearl
River sediments.
Typical marine geology in the seabed of the region
is soft marine deposits underlain by alluvium. The
alluvium is underlain by residual soil and then by
bedrock.
The soft marine deposits are in general silty clays
with silt or sand seams and partings. The thickness of
the marine deposits depends on depths of erosion prior
to the Flandrian transgression.
Alluvium (fresh water deposits of interbedded
alluvial clay and alluvial sand formed on stream beds
and flood plains) often exists above the decomposed
rock and below the soft marine deposits. It is composed
of interbedding alluvial clay and alluvial sand.
Atterberg limits of the soft marine deposits and the
alluvial clay collected by the author are presented in
Fig. 3. It can be observed that almost all the data points
lie in a narrow band parallel and slightly above the
A-line. No distinction between the soft marine deposits
and the alluvial clay in terms of Atterberg limits can be
observed; suggesting that the engineering behavior of
the two clays is very similar. They are collectively
denoted as marine clays and can generally be classified
as clay of upper plasticity range using the British Soil
Classification System, i.e., LL > 35%.
Fig. 3. Plasticity chart of soft marine deposits and alluvial clay
The locations of data points on the plasticity chart
shown in Fig. 3 indicate the predominant mineral in the
marine clays is illite (Holtz & Kovacs 1981). The
finding is consistent with those obtained from a
comprehensive study of the microfabric, mineralogy
and chemistry of marine clay samples obtained from
Chek Lap Kok (Tovey 1986). The study undertaken
includes: (1) qualitative and quantitative mineralogical
analysis by X-ray diffraction; (2) microfabric analysis
by scanning electron microscope; (3) chemical analysis
of solid particles using X-ray fluorescence analysis; and
112
(4) chemical analyses of pore fluid using atomic
absorption spectrophotometry for cations and ion
exchange chromatography for anions.
Both the peak and remolded undrained shear
strength of the uppermost marine clay increase with
depth indicating the clay is normally consolidated. The
Su/σv' ratio is approximately 0.30 and 0.11 for peak
strength and remolded strength, respectively, where Su
= undrained shear strength; and σv' = in-situ effective
vertical overburden stress. Moreover, the sensitivity of
the clay is approximately 2.85 (Yeung & So 2001).
The effective shear strength parameters of the
marine clays measured in consolidated undrained
triaxial tests are c' = 0 and φ' = 30°. There is practically
no distinction between the soft marine deposits and the
alluvial clay in terms of effective shear strength
parameters. The measured friction angle is also
consistent with the range of the measured values of
plasticity index (Terzaghi et al. 1996).
The laboratory measured compression index Cc is in
the range of 0.15 and 1.03 with an average value of
0.31 that is typical for clays of low plasticity. However,
it should be noted that the average compression index
of the soft marine deposits is approximately 0.6 and
that of the alluvial clay is approximately 0.2. Although
the soft marine deposits and the alluvial clay can be
considered as a single material in terms of index
properties and shear strength parameters, there is a
significant difference in their compressibility. The
difference is probably caused by the difference in stress
history between the soft marine deposits and the
alluvial clay.
The coefficient of consolidation of the marine clays
has exhibited considerable natural variability ranging
from 1-9 m2/yr. The coefficient of consolidation in the
vertical direction due to horizontal drainage is at least
twice that due to vertical drainage, rendering
prefabricated vertical drains an effective means to
accelerate consolidation settlement and to increase
shear strength of the marine clays (Yeung & So 2001).
The marine clays are normally consolidated, highly
compressible and often too weak to support the
reclamation and any major infrastructures to be built on
it without special treatment (Lee & Ng 1999; Yin 1999,
2002; Yeung & So 2001; Zhu & Yin 2001). Therefore,
they were often dredged and dumped in past
reclamation projects in Hong Kong, including the
reclamation of Airport Island for the construction of the
HKIA (Fung et al. 1984; Foott et al. 1987; Koutsoftas
et al. 1987; Koutsoftas & Cheung 1994).
The granite bedrock underneath the region is
decomposed to depths of more than 70 m below the
present sea level. For decomposition to occur, there
must be percolation of fresh water through the rock
joints. Therefore, the sea level in the past must have
been much lower than that at present to have allowed
such decomposition to occur.
5 THE SEA-CROSSING
The sea-crossing will follow a route east to west
from the HKBCF, passing through Hong Kong waters,
then continuing to the west along the north side of the
Dayushan Y3 Anchorage (23DY), before crossing
several navigation channels, i.e. Tonggu Navigation
Channel (銅鼓航道西線), Lingding West Channel (伶仃
西航道
)
, Qingzhou Channel (青洲航道), Jianghai
Channel (江海直達船航道) and Jiuzhou Channel (九洲
港航道), and to finish at the artificial island of the
ZMBCF as shown in Fig. 4. The total length of the
crossing is approximately 41.6 km, of which 12 km is
in Hong Kong territory and 29.6 km is in Guangdong
waters.
Fig. 4. A layout of the Main Bridge-cum-Tunnel
The boundary crossing facilities will be constructed
and administered independently by the three regional
governments under the "three regions, three custom
inspections" system. The boundary crossing facilities
for Hong Kong will be located in Hong Kong. Details
of the HKBCF are given in a later section in this paper.
The boundary crossing facilities for Mainland China
(Zhuhai) and Macao will be co-located on an artificial
island of 208.87 ha in Guangdong waters immediate
east to Gongbei, Zhuhai/Macao. The artificial island
consists of four distinct areas: (1) the administration
facilities of the HZMB; (2) the connecting area in
Zhuhai; (3) the Zhuhai Boundary Crossing Facilities
administrative area; and (4) the Macao Boundary
Crossing Facilities administrative area. The reclamation
for the artificial island was completed on 28th
November, 2013 as shown in Fig. 5.
Fig. 5. Reclamation fo
r the Zhuhai/Macao Boundary Crossing
Facilities
113
The link road to Zhuhai starts at the Zhuhai
Boundary Crossing Facilities on the artificial island,
passes Wanzai (灣仔) and the north side of Zhuhai Free
Trade Zone (珠海保稅區), and reaches Hongwan (洪灣),
Zhuhai. From there it will connect to a proposed
13.4 km highway to form the PRD regional loop from
Nanping (南屏) to Hongwan. The link road will be
constructed to dual 3-lane expressway standard, with
design speed of 80 km/h, roadbed width of 32 m, total
bridge width of 31.5 m and tunnel width of 2×14 m.
6 MAIN BRIDGE-CUM-TUNNEL
The scheme of using a bridge-cum-tunnel structure
has been adopted for the sea-crossing in the waters of
Guangdong. The Bridge is approximately 22.9 km long
and across Qingzhou Channel, Jianghai Channel and
Jiuzhou Channel. The Tunnel is approximately 6.7 km
long and across Tonggu Navigation Channel and
Lingding West Channel as shown in Fig. 4. Artificial
islands are built at the ends of the Tunnel. West
Artificial Island provides transition of the Bridge to the
Tunnel. East Artificial Island provides transition of the
HKLR viaduct to the Tunnel. Both artificial islands
also accommodate tunnel ventilation shafts. The eastern
edge of East Artificial Island is 150 m west of the
Guangdong/Hong Kong boundary, and the eastern edge
of West Artificial Island is 1.8 km from Lingding West
Channel. The minimum edge to edge distance between
the two artificial islands is approximately 5.25 km. The
layout of the Main Bridge-cum-Tunnel is shown in Fig.
4. The Bridge provides a dual 3-lane carriageway with
a design speed of 100 km/h. The total bridge width is
33.1 m. The design live load for the Bridge complies
with both China's Highway Class I for Bridge Design
Vehicle Loads, and the live load provisions in the
Design Manual for Roads and Railways of Hong Kong.
The designed service life of the Bridge is 120 years.
The construction environment of the HZMB is very
complicated. Frequent typhoons, crisscross navigation,
airport height restrictions, stringent environmental
standards, etc. have to be taken into considerations.
There are stringent requirements to control the water
blockage ratio during the selection of options to
minimize the impact of the Bridge to river flow,
navigation and hydrology. There are approximately 130
bridge piers supported by approximately 1,100 rock
socketed large-diameter bored piles as shown in Fig. 6.
These piles are approximately 100 m long. The pier and
pile cap is precast and installed on site as shown in Fig.
7. The precast bridge segments are then installed atop
the piers as shown in Fig. 8.
The Tunnel also provides a dual 3-lane carriageway
with a design speed of 100 km/h. The Tunnel is of
width 2×14.25 m and vertical clearance of 5.1 m. The
sub-sea Tunnel is the largest and one of the deepest
immersed tube tunnels in the world, as it has to
accommodate three lanes of traffic in each direction
and will therefore have extremely wide spans of nearly
15 m. It is situated some 45 m below the sea level, so as
to ensure safe passage of 300,000 tonne shipping
vessels on Pearl River. Therefore, the Tunnel is
required to resist large hydrostatic and traffic loads.
Moreover, the design has to take into account a design
service life of 120 years in a harsh marine environment,
and the adverse offshore conditions and complicated
navigation environment for transport and immersion of
the tunnel tube elements during construction, making
the design and construction of the sub-sea Tunnel
uniquely challenging.
The sub-sea Tunnel essentially consists of a set of
33 inter-connected precast concrete 'boxes' of typically
Fig. 6. Installed rock socketed large-diameter bored piles
Fig. 7. Installation of precast pier and pile cap
Fig. 8. Installation of bridge segments
114
180 m long as shown in Fig. 9. Weighing over 75,000
tonnes, these tunnel tube elements are the largest in the
world. Having been transported afloat from the
production site to the project location, they are
connected together on the seabed using special rubber
seals to ensure the connection is watertight. The
installation of Tunnel Element E18 is shown in Fig. 10.
After the temporary tunnel ends have being knocked
through, one continuous tunnel structure is created.
Fig. 9. Cross-section of the Tunnel
Fig. 10. Installation of Tunnel Element E18 on 27th June, 2015
The Tunnel is situated between West Artificial
Island and East Artificial Island. The containment
structures of the two artificial islands are built of large
steel cylinders installed by vibratory driving as shown
in Fig. 11. The volumes inside the steel cylinders and
the volumes within the containment structures are then
filled with sand as shown in Fig. 12, after the
installation of prefabricated vertical drains. The
engineering properties of the soft marine deposits in the
seabed within the containment structures are improved
by surcharging with prefabricated vertical drains. Sand
compaction piles are installed around the perimeters
outside the containment structures as shown in Fig. 12
to support the seawall revetments. A cross-section of
the artificial island indicating different methods of
ground improvement is depicted in Fig. 13. The
construction method minimizes the dredging and
dumping of soft marine deposits.
7 THE HONG KONG BOUNDARY CROSSING
FACILITIES
The Hong Kong Boundary Crossing Facilities
("HKBCF") will be located on an artificial island of
approximately 150 ha reclaimed from Hong Kong
waters off the northeast coast of the HKIA as shown in
Fig. 14.
The construction works of the HKBCF include
cargo and passenger clearing and vehicle inspection
facilities, offices for frontline departments of the
HKSARG, such as the Immigration Department, the
Customs and Excise Department, etc., road networks,
public transport interchange and associated civil, traffic
control surveillance system and landscaping works, etc.
Geographically, the HKBCF are at a convenient
location of excellent transportation connectivity, as it is
linked by the HKLR, the TM-CLKL (in the north and
southeast) and the highways leading to the HKIA.
Moreover, as it is adjacent to the HKIA and near the
Fig. 11. Installation of large steel cylinder by vibratory driving
Fig. 12. Installation of sand compaction piles
Fig. 13. Cross-section of east and west artificial island showing
different methods of ground improvement
115
Tung Chung new town, there are a variety of means of
transportation facilities, including the HKIA, the
SkyPier, the MTR Airport Express Line and the MTR
Tung Chung Line, available in the proximity.
Fig. 14. Layout of the Hong Kong Boundary Crossing Facilities
The HKIA is also known as Chek Lap Kok Airport
as it was built on a largely artificial island reclaimed
from Chek Lap Kok Island. It handled 63.3 million
passenger trips and 4.38 million tonnes of cargoes in
2014. With approximately 1,100 aircraft movements
and more than 100 airlines linking the HKIA with
approximately 180 destinations worldwide every day, it
is one of the world's busiest passenger airports and the
world's busiest cargo gateway. It has been consistently
voted one of the top five airports in the world.
The SkyPier at the HKIA provides speedy ferry
services for transfer passengers, making the HKIA a
truly multi-modal transportation hub for convenient air
and sea travel. The SkyPier serves these nine ports in
the PRD: (1) Dongguan Humen ( 東莞虎門); (2)
Guangzhou Lianhuashan (廣州蓮花山); (3) Guangzhou
Nansha ( 廣州南沙); (4) Macao (Maritime Ferry
Terminal) [澳門(外港客運碼頭)]; (5) Macao (Taipa) [澳
門(氹仔)]; (6) Shenzhen Fuyong (深圳福永); (7)
Shenzhen Shekou (深圳蛇口); (8) Zhongshan (中山);
and (9) Zhuhai Jiuzhou (珠海九洲).
The HKBCF will become a multi-modal
transportation hub in the area. The road traffic of the
area will be well connected since HZMB vehicles can
use other routes in case any one of them becomes
unavailable for whatever reason. The traffic at the Tung
Chung new town will also be improved as traffic can
use the Southern Connection of the TM-CLKL to
bypass the Tung Chung new town. Details of the
TM-CLKL are given in a later section of this paper.
Conventionally, seawalls for reclamation in Hong
Kong were constructed on competent foundations by
dredging the soft marine deposits in the seabed and
replacing them by sand fill. The process requires
dredging and dumping of a large quantity of soft
marine deposits (Plant et al. 1998; Yeung and So 2004),
and the winning of large quantity of sand fill to replace
the soft marine deposits to construct the reclamation.
The adverse environmental and ecological impacts
induced by the process of dredging and dumping of soft
marine deposits are well documented (Sun et al. 2012;
Zainal et al. (2012). Moreover, the winning of sand fill
increases the volume of soft marine deposits to be
dredged and dumped, as sand is always located below
soft marine deposits.
A non-dredging reclamation technique was
developed to reclaim the 150-ha artificial island for the
HKBCF, including approximately 20 ha of land for the
Southern Landfall of the TM-CLKL sub-sea tunnel, so
as to minimize the environmental and ecological
impacts of dredging and dumping of soft marine
deposits. This is the first time this new reclamation
technique is used in Hong Kong.
The 6,140 m long containment seawall of the
artificial island will be formed by sinking 134
large-diameter circular steel cells of diameter 27 m or
31 m constructed of steel sheetpiles through the soft
marine deposits. These steel cells are then filled up by
inert construction & demolition ("C&D") materials or
sand. In Hong Kong, C&D materials are defined to be
any substance generated by construction or demolition
activities, regardless of whether or not it has been
processed, stockpiled or abandoned. Inert C&D
materials are also known as public fill in Hong Kong,
including rocks, concrete, asphalt, rubble, bricks, stones
and earth. The remaining non-inert substances in C&D
materials include bamboo, timber, vegetation,
packaging materials, and other organic and perishable
materials. Non-inert C&D waste is not suitable for land
reclamation and/or other applications. Subject to
recovery of reusable/recyclable items, it is disposed of
in landfills (Yeung 2008).
The construction of the reclamation for the artificial
island has also adopted the non-dredging method.
Prefabricated vertical drains are installed in the soft
marine deposits to accelerate their consolidation.
Design methodology for prefabricated vertical drains is
suggested by Yeung (1997). A piece of geotextile and a
2-m thick sand blanket are laid over the soft marine
deposits prior to reclamation filling. As such, there will
basically be no dredging and dumping of soft marine
deposits for the HKBCF reclamation.
The adoption of the non-dredging reclamation will
greatly reduce the amount of dredging and dumping of
soft marine deposits by approximately 22 Mm3, and
will also reduce the use of backfilling materials by
approximately one half. As a result, there is much less
impact to the water quality and marine ecology.
Furthermore, there is a significant reduction in the
construction marine traffic for transportation of dredged
materials from the site and backfilling materials to the
site during the reclamation process. This will help to
preserve the marine ecology especially the Chinese
White Dolphins habitats. The statistics of the many
green benefits offered by the non-dredging reclamation
116
construction method over the conventional dredging
reclamation construction method will be discussed in a
later section of this paper.
8 THE HONG KONG LINK ROAD
The Hong Kong Link Road ("HKLR") is a dual
3-lane carriageway connecting the Main Bridge-cum-
Tunnel at the Guangdong/Hong Kong boundary to the
HKBCF as shown in Fig. 15.
Fig. 15. Layout of the Hong Kong Link Road
The HKLR comprises a 9.4 km long viaduct section
from the Guangdong/Hong Kong boundary to Scenic
Hill on the Airport Island; a 1 km tunnel section from
Scenic Hill to the reclamation formed along the east
coast of the Airport Island and a 1.6 km long at-grade
road section on the reclamation to the HKBCF.
The viaduct section is the first bridge designed in
Hong Kong using a precast pier structure. The
construction team is faced with a variety of challenges,
including severe marine conditions, complex navigation
requirements, restricted land access, airport height
restrictions, stringent dolphin protection requirements,
deep rock head levels, the need to supply concrete
using a floating batching plant, and the logistics of
transporting concrete trucks on Ro-Ro barges.
The floating batching plant, a first in Hong Kong,
facilitates marine production of concrete and
significantly reduces marine and land traffic during
construction. As a result, air and noise pollution are
minimized.
The tunnel section of HKLR will pass under Scenic
Hill, Airport Road and the MTR Airport Railway to
minimize the environmental and visual impacts to the
residents of the Tung Chung new town.
9 THE TUEN MUN-CHEK LAP KOK LINK
The TM-CLKL comprises a 9-km long dual 2-lane
carriageway connecting Tuen Mun and north Lantau.
The layout of the route is shown in Fig. 16. The
alignment commences at a connection with the North
Lantau Highway at Tai Ho Wan of Lantau. From the
connection it heads northwest on a 1.6 km long sea
viaduct to the HKBCF. This section of the TM-CLKL
is denoted as the Southern Connection of TM-CLKL.
After landing on the eastern edge of the artificial island
accommodating the HKBCF, the alignment turns north
and heads into a 5-km long sub-sea tunnel from the
Southern Landfall, i.e. the Northern Connection of the
TM-CLKL. The toll plaza is situated further north in
Tuen Mun Area 46 to reduce the extent of reclamation
of the Northern Landfall. More details of the
TM-CLKL are depicted in Fig. 17.
Fig. 16. Layout of the Tuen Mun-Chek Lap Kok Link
The construction contract of the Northern
Connection involves the design and construction of a
dual 2-lane sub-sea tunnel of approximately 5 km long
between the HKBCF and Tuen Mun Area 40, and
reclamation to form extra land of approximately
16.5 ha at Tuen Mun Area 40 as the Northern Landfall
of the sub-sea tunnel of TM-CLKL.
As the deepest, longest and largest sub-sea road
tunnel ever built in Hong Kong, the sum of the
construction contract is also the largest ever awarded in
Hong Kong, reflecting the scale and complexity of the
project.
The world's largest tunnel boring machine of 17.6 m
in diameter and two identical mix-shield tunnel boring
machines of 14 m in diameter will be used to construct
these road tunnels. The adoption of tunnel boring
machines for the construction of these sub-sea tunnels
will avoid the dredging and disposal of some 11 Mm3
of soft marine deposits required for tunnel construction
by the traditional immersed tube method. Moreover,
these state-of-the-art machineries are equipped with
in-house innovations of the contractor, namely
MOBYDIC, SNAKE and TELEMAC, which enable
real-time geological mapping of rock faces, and robotic
detection of damaged components on the cutter heads
to reduce manual inspections under hyperbaric
conditions.
Working under a compressed-air environment is the
key challenge of this project. The project team has
proposed to use a saturation technique for maintenance
works on the cutter heads of the tunnel boring machines,
117
so as to maximize the health and safety of workers, and
to enhance construction efficiency.
Sustainable measures are in place during and after
construction, such as recycling excavated materials
from the north reclamation as backfilling of the launch
shaft or returning it as public fill. The two ventilation
buildings will attain a Hong Kong BEAM Plus Gold
rating upon completion. Wind turbines will also be
built in both buildings for renewable power generation.
10 TUEN MUN WESTERN BYPASS
The Tuen Mun Western Bypass ("TMWB") is a
dual 2-lane highway tunnel of approximately 4.8 km
long connecting the TM-CLKL in the south and Tsing
Tin Road in the north as shown in Fig. 18. Strategically,
the TMWB, together with the TM-CLKL, will provide
a north-south highway corridor linking the northwest
New Territories with the HKBCF, the HKIA and north
Lantau. The project is still in the consultation stage.
Fig. 18. Layout of the Tuen Mun Western Bypass
11 GREEN MEASURES
Many green measures are being implemented during
the design and construction stages of the HZMB Project,
in particular the components contributed by the
HKSARG. These green measures are briefly discussed
as follows.
10.1 Minimization of environmental impacts
Various site and alignment options of the HKBCF,
HKLR and TM-CLKL have been examined, and the
views obtained from extensive public consultation since
2007 have been considered to minimize environmental
impacts of the HZMB Project including:
1) The HKBCF is located at the waters off the
northeast of the Airport Island so that it is away
from major active areas of the Chinese White
Dolphin. The location also has comparatively less
impacts on the environment, hydraulics and
navigation safety. Furthermore, it avoids impact on
the natural hillsides and shorelines.
2) The HKBCF is at a distance of 2 km away from the
Tung Chung new town to minimize air quality,
noise and visual impacts on the residents.
3) The reclamation of the HKBCF and that for the
Southern Landfall of the TM-CLKL sub-sea tunnel
are integrated and constructed together to reduce
the total length of seawalls by approximately
1.8 km. Moreover, the reclamation is constructed
by a non-dredging reclamation method.
4) Natural rock amours are adopted on reclamation
seawalls to mitigate visual impact.
5) The alignment of the HKLR will run along the
Airport Channel at the southern side of the Airport
Island which is away from the ecological sensitive
Fig. 17. Details of the TM-CLKL
118
areas such as the San Tau Site of Special Scientific
Interest, as well as the nursery sites of the seagrass
and horseshoe crab.
6) A tunnel-cum-at-grade road scheme for the HKLR
is adopted in lieu of the all-viaduct scheme for the
section from Scenic Hill on the Airport Island to
the HKBCF to minimize visual impacts.
7) The HKLR viaduct will straddle the headland
between San Shek Wan and Sha Lo Wan without
affecting the natural shorelines of the Lantau
Island.
8) The pile caps of the HKLR viaduct in the Airport
Channel are below the seabed level to minimize
hydrodynamic impacts.
9) The adoption of a sub-sea tunnel for the Northern
Connection of the TM-CLKL has avoided the
marine habitat at Tai Mo To.
10) The sub-sea tunnel will be constructed by tunnel
boring machines in lieu of the traditional immersed
tube method to avoid dredging and disposal of
some 11 Mm3 of marine sediments, so as to
minimize the overall impacts on the seabed, water
quality, marine environment and habitats.
11) The Southern Connection of the TM-CLKL will be
in the form of a sea viaduct, providing a direct
connection between the HKBCF and the North
Lantau Highway. The direct connection will avoid
the traffic through the Tung Chung new town and
alleviate the traffic and environmental impacts in
the area.
12) The TM-CLKL Toll Plaza is relocated from
reclaimed land of the Northern Landfall to Tuen
Mun Area 46 to reduce reclamation.
13) A comprehensive Environmental Monitoring and
Audit (EM&A) program is implemented during
construction to monitor regularly the impacts on
various environmental aspects including air quality,
noise, water quality, waste management and
ecology including the Chinese White Dolphin, etc.
on the nearby sensitive receivers and areas which
may be affected by the construction works of the
HZMB Hong Kong projects.
14) The HKSARG will seek to designate the Brothers
Islands as a marine park in compliance with the
Marine Parks Ordinance upon completion of the
Project to further enhance conservation of the
environment.
15) Approximately 10,000 m3 of artificial reefs would
be deployed as replacement and compensation to
affected marine habitats.
16) Fish fry will be released at the new artificial reefs
as well as the existing artificial reefs in Sha Chau
and Lung Kwu Chau Marine Park to enhance the
fish resources in the western Hong Kong waters.
Fig. 19. Chinese White Dolphin
10.2 Preservation of the Chinese While Dolphin
habitat in Hong Kong
The Chinese White Dolphin, as shown in Fig. 18, is
active in the vicinity waters of the HZMB Project. In
the design stage, the locations and alignments of the
HZMB components within Hong Kong waters are
carefully chosen to avoid major active areas of the
Chinese White Dolphin. During construction, various
mitigation measures are implemented to minimize
potential impacts to the Chinese White Dolphin
including:
1) Non-dredging methods are adopted for reclamation
and seawall construction to reduce the amount of
marine ecological disturbance caused by the
dredging and disposal operations.
2) No underwater percussive piling is allowed.
3) No formation of underwater rock sockets for bored
piles is allowed during the peak dolphin calving
season in May and June.
4) Noisy construction equipment mounted on marine
construction vessels is acoustically-decoupled to
minimize underwater noise.
5) Marine construction vessels have to follow
pre-defined regular travel routes to avoid the active
areas of Chinese While Dolphins.
6) Marine construction vessels have to travel at a
speed lower than 10 knots in the areas of work site,
marine park and proposed marine park.
7) Skipper of marine construction vessels working in
the areas have to undergo specific training on local
dolphins and porpoises.
8) A dolphin exclusion zone (DEZ) of 250 m radius is
implemented during the silt curtain installation and
the bored pile casing installation works. Works will
be suspended if any dolphin is found within the
DEZ.
9) Silt curtain enclosed areas are regularly checked
and works will be suspended if any dolphin is
found within the enclosed area.
10) The population of Chinese White Dolphins in the
northwestern waters of Hong Kong is regularly
119
monitored.
11) The best available construction practices, such as
employing silt curtain and Y-shaped funnel, etc.,
are adopted to minimize sediment dispersion
during construction (Yeung et al. 2008), and to
avoid impact on water quality.
10.3 Green statistics
The green statistics to be achieved by the HZMB
Project are summarized as follows:
1) The HZMB will open a new and direct connection
route between Hong Kong, Zhuhai and Macao. It
will significantly shorten the journey for the flows
of passengers and cargoes between Hong Kong and
the western PRD region. The new direct route will
also avoid detouring and help minimize use of
fossil fuels and gas emissions by vehicles. From
Zhuhai to the Kwai Chung Container Ports, the
journey distance and traveling time will be reduced
from approximately 200 km and 4 hours currently
to approximately 65 km and 75 minutes,
respectively, a reduction of over 60%. From
Zhuhai to the HKIA, the journey distance and
traveling time will be further reduced from over
200 km and approximately 4 hours to
approximately 40 km and 45 minutes, respectively,
with more than 80% reduction. It helps to reduce
vehicle CO2 emission by at least 1,100 tonne/day.
2) The adoption of the non-dredging method for the
reclamation of the HKBCF reduces the quantity of
soft marine deposits to be dredged and disposed of
by 97%, the quantity of backfilling materials by
50%, and the marine construction traffic by 50%.
3) Combining the reclamations for the HKBCF and
the Southern Landfall of the TM-CLKL sub-sea
tunnel reduces the total length of seawalls by
1.8 km, minimizing the impact on the marine
environment.
4) The adoption of tunnel boring machines for the
construction of the approximately 5 km sub-sea
road tunnel for the Northern Connection of the
TM-CLKL will avoid the dredging and disposal of
some 11 Mm3 of marine sediments required for
construction using the traditional immersed tube
method.
5) The non-dredging method of reclamation will
reduce the quantity of suspended particles by 70%
during construction.
12 SUMMARY
The Hong Kong-Zhuhai-Bridge Project, being
situated at the waters of Lingdingyang (伶仃洋) of the
Pearl River Estuary, is a mega sea-crossing
infrastructure project currently under construction in
the Pearl River Delta of China. It consists of a series of
bridges, sub-sea tunnels, viaducts and artificial islands
connecting the Hong Kong Special Administrative
Region ("Hong Kong") ( 香港), Zhuhai City of
Guangdong Province ("Zhuhai") (珠海), and the Macao
Special Administrative Region ("Macao") (澳門), three
major cities situated on the Pearl River Delta in China.
The geotechnical works associated with the HZMB
Project, including reclamations, onshore and offshore
foundations, sub-sea tunnels, artificial islands, earth
retaining structures and roadworks are extensive,
large-scale, diversified, challenging and complex.
The background of the mega project and pertinent
geotechnical works of the Project, in particular
components contributed by the Hong Kong Special
Administrative Region Government ("HKSARG"), are
described. Moreover, green measures implemented to
reduce environmental impacts during the design and
construction stages of the Project are also presented in
this special lecture.
ACKNOWLEDGEMENTS
Most information used for the preparation of this
special lecture is excerpted from the HZMB website
developed by the Hong Kong-Zhuhai-Macao Bridge
Authority (港珠澳大橋管理局), i.e. www.hzmb.org,
the HZMB website developed by the Highways
Department of the HKSARG, i.e. www.hzmb.hk, and
the website of the Highways Department of the
HKSARB, i.e. http://www.hyd.gov.hk/. These sources
of useful information are gratefully acknowledged.
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