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36 Engineers Australia | May 2013

and stable economic foundations built up by generations of Hong Kong people over decades, we were able to ride out the storm.”

However, he still noted growing pains for the region: “The deep-seated problems of Hong Kong cannot be solved overnight, but we need to take the first step to deal with them now. We must act with one heart and one vision to tackle these problems.”

Setting out its vision in the budget and in the HK2030 study, the Hong Kong government has put in place its framework to guide development of major infrastructure to meet the challenges for the next 20 to 30 years.

The treasury of Hong Kong is forecasting economic growth of up to 3.5% this year and is aiming for a fiscal surplus of A$8.2 billion. It has an unemployment rate of 3.4%, and Tsang said the capital works expenditure will reach A$8 billion in the 2013/14 budget, creating a further 75,000 job opportunities.

“[As of March], our commitments for capital projects were expected to be over A$40 billion,” Tsang said.

Hong Kong Institution of Engineers (HKIE) president Prof Kin Kuen Choy and chief executive Monica Yuen visited Australia earlier this year, including a stop over at Engineers Media. Here, they outlined the significant infrastructure projects taking place throughout Hong Kong.

The construction of five new railway lines is now under way and upon completion the rail network will cover an area within which over 70% of Hong Kong’s population lives. These projects are covered in further detail in Growth spurt for passenger rail (pp 40-41).

Meanwhile, the traffic gridlock problem is also trying to be resolved and major road projects include the Central-Wan Chai Bypass and Island Eastern Corridor Link. Significant traffic congestion is expected to be alleviated upon completion in 2017.

The detailed design of a second road tunnel linking Tseung

When you visit Hong Kong, there is a sense of futur-ism about the place. It is like the city is showing people from other countries what to expect in the

future, as population and urbanisation continues to rapidly build around the world.

Hong Kong is a hive of activity. Victoria Harbour shimmers and shines in between commercial hubs of tall buildings, shopping centres and offices, with their bright lights and their claustrophobic contribution to the buzz of a thriving city. The buildings even feature in a nightly Symphony of Lights show across the harbour as residents and tourists alike sit harbour-side and enjoy the spectacle.

From the city, through the suburbs and up the mountainside, the skyline is strung with high-density housing. Among the housing, one can note a fierce protection of the remnant nature strips and parklands. A highly connected public transport system seamlessly transports people between places, but at ground-level there is a hint of craziness as old vehicles in gridlocked streets belch into a thick air of pollution.

“In almost every movie and TV drama series featuring Hong Kong, you are likely to come across queues of vehicles along roads and crowds of pedestrians jostling against each other amid the hustle and bustle of the city,” Hong Kong financial secretary John C Tsang said in his 2013/14 budget address in March. “You can feel a unique buzz. Call it hectic or even chaotic, our seven million people may have seven million different lifestyles, seemingly unconnected to each other, [but] we share the same vision and values that unite us and drive us to forge ahead.”

Despite a difficult global climate of investment, Hong Kong is continuing to grow and is setting itself up as a gateway to mainland China. Since Hong Kong returned to Chinese rule in 1997, it has experienced several periods of ups and downs, including two financial crises.

Tsang said: “Thanks to the sound institutional framework

KHONGHONG

ONGONGby Danny Cameron

36-47 g - Cover.indd 3636-47 g - Cover.indd 36 9/05/13 12:17 PM9/05/13 12:17 PM

Engineers Australia | May 2013 37

“You can feel a unique buzz.

Call it hectic or even chaotic,

people seemingly unconnected

share the same vision.”

COVER STORY

one heart and one visionto tackle problems

Kwan O and urban Kowloon, as well as planned Tuen Mun-Chek Lap Kok Link will both start within the year.

The largest road project in the region is the Hong Kong-Zhuhai-Macau Bridge, a series of bridges and tunnels connecting Hong Kong, Macau and Zhuhai. The proposed 50km link is expected to cost more than A$10 billion and is scheduled to open in 2016.

The government is also investing in health infrastructure as an ageing population puts increasing strain on the system. Late last year, the Hong Kong government celebrated the construction of the North Lantau Hospital. The expansion of Tseung Kwan O Hospital and the phase two redevelopment of Caritas Medical Centre will be completed in 2013 and 2014 respectively.

The government is also preparing for the redevelopment of Queen Mary Hospital, Kwong Wah Hospital and United Christian Hospital. The estimated costs will be as high as A$3 billion. In addition, A$2.5 billion will be made available for the construction and refurbishment of several other public hospitals and clinics, including the construction of Tin Shui Wai Hospital and the refurbishment of HK Buddhist Hospital.

On the environmental front, the success of Hong Kong’s

Harbour Area Treatment Scheme Stage 1, which has seen significant improvement in the overall water quality of Victoria Harbour, is now being followed with the A$2.2 billion Stage 2A phase. This is scheduled for completion in 2014.

The environment is a particular area of attention for the Hong Kong government. With air pollution an obvious and significant problem, the government has set aside A$1.25 billion for subsidies to owners of over 80,000 pre-Euro IV diesel commercial vehicles, to progressively phase out the vehicles. This initiative alone has been estimated to reduce overall emissions of particulates by 80% and nitrogen oxides by 30%. The government will also help franchised buses, taxis and mini-buses reduce emissions, starting with an announcement to subsidise trials of hybrid buses and fully electric buses by the franchised bus companies in the next financial year. These are part of concerted efforts to improve air quality and meet new air quality objectives by 2020.

The government is also exploring new water sources as the demand for fresh water resources increases as dense urbanisation reaches into new areas. Last year, the government started a detailed planning and investigation study, including an assessment of the feasibility and cost-effectiveness, for the construction of a desalination plant on a reserved site in Tseung Kwan O. Although the anticipated output capacity of the desalination plant will only account for 5%-10% of Hong Kong’s total water consumption, the government envisage that as technology advances and costs go down, seawater desalination can serve as another water supply source and help reduce Hong Kong’s reliance on other water sources.

With all these developments under way, the demand for international engineering skills is strong and the opportunities plentiful. In this feature, Engineers Australia magazine takes a closer look at the international engineering efforts going into some of these and other projects, as Hong Kong continues on its path of building the future vision. ■

HONGONG


COVER STORY


With an ever

globalising

workforce,

labour

mobility

will remain

critical to

effective

engagement

with our

Asian

neighbours.

Forming global partnershipsby Dr Marlene Kanga

E ngineering is an interna-tionalised profession with an increasingly mobile

work force. Young engineers now routinely travel and work internationally as part of their career development. One of the important benefits that Engineers Australia provides to its members is the international recognition of chartered and Australian tertiary engineering qualifications.

Engineers Australia is a signatory to a number of accords that recognise Australian engineering university and TAFE qualifications. Engineers Australia also has mutual recognition agreements with kindred organisations based in Asia, including the Hong Kong Institution of Engineers (HKIE).

Under Hong Kong legislation, engineers working in Hong Kong must be corporate members of the HKIE or a body recognised by HKIE. Approximately 99% of engineers working in Hong Kong are members of HKIE. The remainder are members of bodies such as Engineers Australia, which is recognised via the mutual recognition agreement with HKIE.

In addition, Engineers Australia has a long-standing working relationship with HKIE. For example, Engineers Australia and HKIE undertake joint accreditation visits to engineering educational institutions in signatory countries of various accords to ensure that engineering education standards are being maintained.

The chair of the Sydney Accord Monitoring Team, which monitors educational standards for engineering technologists, is from the University of Hong Kong, a member of HKIE and is visiting Australia in 2013 to audit Australian programs.

The mentors and reviewers for Taiwan’s application for recognition of its engineering education for technologists under the Sydney Accord were jointly from Australia and Hong Kong. Similarly, mentors and reviewers for Germany’s applications for international recognition of its engineering degrees under the Washington Accord, made in January 2012,were f rom t he resp e c t ive engineering institutions of Ireland, Australia and Hong Kong.

In Asia, Engineers Australia enables chartered engineering professionals to be listed on the APEC Engineers Register which provides quality assurance on the competence of engineers working in Asia, including Hong Kong. This is a great example where Engineers Australia facilitates the ability of engineers who have qualified in Australia to be employed in Asia, with assurance of their competency to practice in their particular field.

With an ever globalising workforce, labour mobility will remain critical to effective engagement with our Asian neighbours.

Engineering professionals of the 21st century will increasingly operate across borders, and it is here that Engineers Australia’s investment in productive global partnerships will be so crucial to our success. ■

Dr Marlene Kanga is national president of Engineers Australia.

Hong Kong Institution of Engineers (HKIE) president Prof Kin Kuen Choy stands left of Engineers Australia national president Dr Marlene Kanga, together with chief executives Monica Yuen (HKIE – third from left), Stephen Durkin (EA – fifth from left), Ben Leaver (EA executive general manager – second from left) and other members at a meeting on 11 March at the HKIE offices.


Engineering the Future MTR, Hong Kong

Laing O’Rourke is currently delivering four high-profile rail infrastructure upgrades for Hong Kong’s MTR Corporation, one of the world’s largest mass transit providers. The projects are:

• Contract810B:WestKowloonSouth• Contract811A:WestKowloonNorth• Contract901:AdmiraltyStationandSCLEnabling• TseungKwanOLineMaintenance Laing O’Rourke is Australia’s largest privately owned engineering and construction solutions company. Founded on 164 years of experience, the group has a global presence, with significant operations in the northern and southern hemispheres. We fund, design, manufacture, construct and maintain the built environment - providing the facilities to accommodate, educate, employ, connect and sustain communities.

phone: +61 9903 0300 web: laingorourke.com

COVER STORY


Gold awards for work performance

I In difficult tunnelling conditions, the Hong Kong MTR Corporation has recognised project quality, safety and environmental engagement by presenting Leighton Con-

tractors (Asia) with a Gold Quality Award and Grand Safety Award for its work on the Express Rail Link.

Leighton Contractors is currently working on a 7.65km section of the Guangzhou-Shenzhen-Hong Kong Express Rail Link (XRL), where it is constructing 5km of twin-track tunnels, a pair of single-track tunnels, ventilation buildings as well as temporary magazines for storing explosives.

The Gold Quality award recognised 95% of the tunnelling work passing first inspection, while also noting Leighton Con-tractors’ internal controls that ensure mistakes are resolved

quickly and not repeated. This included the use of external quality auditors and examiners.

Leighton Contractors highlighted the use of high quality formworks that were designed specifically for the project. The formworks designed and developed by CIFA and CAD2000 include safe access, vibration ports and easy access.

The company also noted the performance of specialist subcontractor Metro-Specialist for waterproofing and lining, and the use of high quality membranes from Mapei.

The safety award recognised zero reportable incidents over the six month period to December 2012, as well as lighting, ventilation and traffic control measures that were above standard requirements.

Growth spurt for passenger rail

T hirty four years after it opened, Hong Kong’s commuter railway MTR Corporation (MTR) is

undergoing a new growth spurt with five new rail extension projects to be completed within the next decade.

The first of these works commenced in July 2009 and will be completed in 2014. These works are occurring along the West Island Line, a 3km extension of the Island Line, which will include stations at Sai Ying Pun, the University of Hong Kong and Kennedy Town. In accordance with the existing line, a capacity of up to 85,000 passengers per hour per direction will be facilitated.

The A$2 billion extension is being completed in a total of 57 civil and E&M (electrical and mechanical) contracts. The tunnelling alone is being completed in three contracts awarded to the Dragages Maeda BSG joint venture, the Gammon Nishimatsu West Island Line joint venture

and Gammon Construction.A major milestone on the project

was reached in November with the breakthrough of the railway tunnel from Sheung Wan Station to Kennedy Town Station.

Another was reached only last month with the topping-out of Kennedy Town Station, the first of West Island Line’s three stations to be topped-out. Kennedy Town Station is a two-level structure with three entrances.

A ceremony held at the site signified the completion of civil works for the ter-minus station and the start of electrical, mechanical and other fitting out works as well as the laying of tracks.

“This is a really exciting moment in the construction of the West Island Line. We’re turning an important corner to start putting in the railway systems and facili-ties that will allow us to operate trains all the way from Chai Wan to Kennedy

Town,” MTR Corporation chief execu-tive officer Jay Walder said. “Building a railway in a densely populated area such as Western District is full of challenges.”

To date, 75% of the overall civil works have been completed and the other two stations at the University of Hong Kong and Sai Ying Pun are expected to be topped-out shortly. Major civil works are expected to be completed by the end of the year, with electrical and mechanical works completed in 2014.

When the West Island Line opens, a journey from Kennedy Town to Sheung Wan will take only 8min, down from the present 15min to 25min.

The second project to commence con-struction was the A$8 billion Express Rail Link in January 2010, with completion targeted for 2015. The 26km Hong Kong section of the Guangzhou-Shenzhen-Hong Kong Express Rail Link runs from West Kowloon in Hong Kong to the

“Building a railway in

a densely populated

area such as Western

District is full of

challenges.”



COVER STORY


To improve environmental performance on the project, the company noted an effort to reduce rock wastage from the tunnelling works by processing excavated rock for use in a drainage layer under the invert of the tunnel instead of re-importing drainage material and removing excavated rock. It is excavating around 3.5Mt of rock in all the tun-nelling works, and approximately 85,000t will be reused as drainage material.

While the majority of the main tunnels are being con-structed within underlying bedrock, one of the main chal-lenges being faced is the faulting that occurs throughout the region. The contractors expect to face poor rock and higher groundwater conductivity within fault zones. ■

boundary of Hong Kong and Shenzhen. The Express Rail Link will connect the city with the 16,000km Chinese national high-speed railway network.

The project is being delivered in 38 major contracts, including a A$1 billion contract to the Leighton Gammon joint venture for the West Kowloon Termi-nus Station North. Other engineering contractors include Bachy Solentanche Group, Hsin Chong Construction, Laing O’Rourke, the Jardine Engineering Cor-poration, Dragages, Bouygues, Thyssen-Krupp, Nuctech and ATAL Engineering.

Earlier this year, Leighton Contractors (Asia) was awarded a Gold Quality Award and Grand Safety Award for its work on a 7.65km section of tunnelling works [see Gold awards for work performance below].

On the third project, construction on the Shatin to Central Link commenced last year. The 17km link line is a territory-wide railway project with 10 stations,

including six interchange stations. Upon completion, passengers will be able to travel directly from Diamond Hill Station to the East and West New Territories, Kai Tak, Kowloon City and Hung Hom without needing to change trains. The Tai Wai to Hung Hom Section is expected to be completed in 2018 while the Hung Hom to Admiralty Section will have to interface with other infrastructure proj-ects, including Wan Chai Development Phase II and Central-Wan Chai Bypass, and is expected to be completed in 2020.

The Shatin to Central Link celebrated its first project milestone on 18 December with the topping out ceremony for the new Central Mail Centre in Kowloon Bay. The six-storey building with a gross floor area of 21,000m2 has been built under a reprovisioning project to replace the ex-isting International Mail Centre in Hung Hom and cater for the future development needs of Hong Kong’s postal services.

The International Mail Centre will be relocated to the new building in Kowloon Bay in mid-2014. The existing structure in Hung Hom will then be demolished to make way for the construction of the Shatin to Central Link.

MTR Corporation projects director TC Chew said Hong Kong’s construction industry is entering into a challenging and intensive period, with the five railway projects alone set to generate 17,000 job opportunities in the sector over the next five years. ■


(l-r) Artist’s impression of MTR’s Admirality Station, South Island Line viaduct works, and South Island Line Wong Chuk Hang depot site. (Below) West Kowloon Terminus under construction in March.


COVER STORY


Pioneering a new tunnelling technique

O ne of four contracts in MTR’s South Island Line (East) Rail extension project is being car-

ried out by John Holland, in partnership with Leighton Asia.

The South Island Line (East) covers approximately 7km from Admiralty Sta-tion to South Horizons Station on the south side of Aberdeen Harbour, with intermediate stations at Ocean Park, Wong Chuk Hang and Lei Tung. The project is located on the island of Ap Lei Chau at the southern side of Hong Kong island and requires extensive construction works to be completed in close proximity to the existing residential estates of South Horizons and Lei Tung. The project also has areas of significant cultural heritage, including 18th and 19th century temples, and historical graves sites.

Work commenced on the new line in May 2011. When completed in 2015 it will provide a fast railway service for communities in the south of Hong Kong Island and help ease traffic congestion at critical bottlenecks like the Aberdeen Tunnel.

The Leighton John Holland joint venture is constructing 1.1km of tun-

nels and two new underground stations at Lei Tung and South Horizons as part of the contract, along with related plant and ventilation buildings. Approximately 1km of the tunnel will be constructed by drill and blast mining techniques, with the remainder using the cut and cover method.

The drill and blast tunnel will be mostly a twin track single-bore tunnel, however, the tunnel splits into two single track tunnels at the approach to the Lei Tung Station. The tunnel then continues as two single track tunnels to the interface with the cut and cover tunnel at Ap Lei Chau Drive. The drill and blast tunnelling work also includes a construction access adit, which will be used for ventilation in the final case, two pedestrian access tunnels and a vertical shaft.

The drill and blast tunnels are pre-dominantly beneath the hill and running through the middle of Ap Lei Chau. The geology along the alignment is typically highly abrasive moderately strong to strong Grade III and II volcanic tuff with compressive strength in the order of 200MPa and above.

The alignment also passes in close

proximity beneath two high-voltage (132kV) cable tunnels, a water reser-voir, steep slopes, retaining walls, water distribution pipes, schools and high-rise housing developments.

Owing to the location of the project and site vibration constraints, the John Holland engineering team said detailed planning and methodology innovations have been required to ensure the most effective and responsible method of con-struction has been used. In particular, the team developed and pioneered the use of “deck loading” in Hong Kong to mini-mise the impacts of blasting operations. This innovation was developed because the planned maximum instantaneous charge weights that could be used in the drill and blast tunnel excavation were se-verely limited as a result of the vibration constraints. The “deck loading” method has been employed in quarrying and shaft works in Australia, Hong Kong and Singapore; however, this was the first use of the method in a tunnelling application in Hong Kong.

The maximum instantaneous charge weight constraints resulted in very low designed explosive weights and this

The tunnelling team developed and pioneered the use of “deck loading” in Hong Kong to minimise the impacts of blasting operations.


COVER STORY


Second decade for Hong Kong Chapterby Scott Smith

The Hong Kong Chapter of Engineers Australia (EAHK) has just finished celebrating its 10th anniversary year.

The chapter was founded in January 2002 and since then has become well established in the Hong Kong Special Administrative Region of China. With over 1200 members, EAHK is the largest overseas chapter of Engineers Australia and one of the largest professional engineering institutions in Hong Kong.

Hong Kong-based Australian organisations find themselves in a collegial environment and this is in no small part due to the strong support provided by the Australian Consul-General to Hong Kong and Macau under the auspices of the Support Australia Group <http://www.hongkong.china.embassy.gov.au/hkng/aus_organ.html>.

EAHK organises continuing professional development activities such as technical talks, short courses and site visits. It also organises social, sporting and community good-will/charity events. Apart from assisting existing Engineers Australia members maintain the currency of their profession, EAHK can also provide professional assessment for new membership. EAHK events offer excellent networking opportunities and can facilitate the ability of the Australian

engineering community to contribute to local Hong Kong needs. Joint events can also facilitate cooperation with other engineering and related institutions based in Hong Kong. A detailed record of EAHK since formation is found on its Facebook site <www.facebook.com/EngineersAustraliaHongKongChapter>.

The EAHK Young Members Committee was recently formed, offering the opportunity for young engineers to considerably broaden their spheres of influence via interaction.

EAHK strives to provide consistent and quality services to Engineers Australia members who are resident in Hong Kong, as well as to members who visit.

EAHK welcomes visitors from Australia and abroad. In addition, Engineers Australia members resident in Hong Kong are invited to register with the chapter. All inquiries can be addressed to [email protected]. Additional details about EAHK can be found on its website <www.eahk.org>. ■

Scott Smith is immediate past president of EAHK. He has returned to Australia and is now foundation professor and Dean

of Engineering at Southern Cross University.

reduced the length of advance per blast. This approach required more blasts for the total length and resulted in extended program duration. To overcome this issue the joint venture team was able to develop the concept of double “deck loading”.

In double “deck loading”, the blast hole is drilled to approximately twice the normal depth and two explosive charges (known as decks) are used within the single blast hole. The technique uses de-lays to initiate the two explosive charges at different times to reduce the amount of explosive detonated at a given instant, which in turn minimises vibration and doubles the advance length achieved in a blast cycle.

Blasting commenced on the project in March 2012 and in April 2012 the first double deck blast was fired. This resulted in an advance of 3.2m, double that which could be achieved with the traditional single explosive deck blast. The first 20 double decked blasts achieved a total of 77m, using a very low average powder factor and double the expected advance

if using a single decked blast design. In July 2012, a 5.8m advance of the 120m2 blast face was fired – resulting in 696 bank cubic metres of rock being broken. The team also reported that fragmentation of all double decked blasts was excellent, enabling mucking-out to be completed in the shortest possible time.

The running tunnel blasting works undertaken from the main tunnelling site at Lee Wing were completed up to Lei Tung Station cavern in early February and also to the South Horizons plant building in late February. The complex blasting sequences for the excavation of the Lei Tung Station cavern and connection tun-nels are ongoing. This work comprises multiple heading and bench excavations to achieve the required design profiles for the large spans in the station cavern.

The John Holland team said the suc-cessful design and execution of double deck tunnel blasts was made possible by the careful design of the initiation se-quence in the blast design. In addition to the benefits achieved on the project by this

innovation in drill and blast tunnelling, the team was able to promote understand-ing for this pioneering technique in Hong Kong where, traditionally, new techniques have difficultly being accepted. ■

The team was able to promote understanding for this pioneering technique in Hong Kong where, traditionally, new techniques have diffi cultly being accepted.


COVER STORY


A new marina development in Hong Kong is using Australian modelling expertise to investi-

gate various breakwater options.The proposed Baroque on Lamma

marina development seeks to reinforce the city’s position as “Asia’s sailing capital” by providing berthing for modern rac-ing and super yachts within a sheltered harbour. However, the site is located on the exposed southern coastline of Lamma Island, facing the South China Sea, where the breakwater design faces significant challenges due to deep water and high-energy wave conditions.

BMT recently completed a review of the concept design of the marina and as-sociated infrastructure, using the services of its Australian arm BMT WBM.

BMT WBM associate Chris Nielsen said it was a challenging task as there were a number of constraints in regards to the breakwater design. These included a proviso that no dredging is to be per-formed, water depths will be up to 24m and design maximal wave heights would be in excess of 8m.

Nielsen said following the completion of an options assessment, a range of vi-able alternative designs were prepared and then ranked according to the key issues of cost, construction methodology,

materials and visual amenity. Breakwater options considered were rubble mounds, caissons and composites.

A “numerical wave flume” was then developed by BMT WBM, using the OpenFoam Computational Fluid Dynam-ics numerical modelling package to assess the breakwater design options.

Nielsen described the numerical wave flume as the computer-based equivalent of a traditional scale-model physical wave flume. It represents all of the relevant hydrodynamic processes associated with waves approaching the breakwater, and the resulting forces and stresses applied to the structure. He said the numerical wave flume can quickly test a range of different options and was used to validate key design parameters. The model was also used to provide a visualisation of the wave impacts on the structure.

The model ran options for conven-tional rock armour, conventional rock armour plus a crestwall, an Icelandic berm breakwater, concrete caisson breakwater, steel breakwater, armour frontage with a cell wall, double caisson, caisson plus wave screen, and caisson plus floating breakwater. In the end, the final concept married the challenging design condi-tions with a U-type precast concrete caisson with berthing, and an inner canal.

Using precast, a single U-shaped struc-ture could be built. The cross-section provides an initial low offshore break-water that absorbs most of the incident (typhoon-generated) storm wave energy but is overtopped during highest wave conditions. The smaller inner breakwater then absorbs the remaining energy gener-ated by any waves overtopping the outer breakwater. The design has a broad flat base which provides foundation stabil-ity against sliding and overturning, and can be precast remotely and deployed in units.

To improve the visual and recreational amenity, the final seawall design was specifically shaped to create more natural forms and a series of steps down to the canal were considered to provide recre-ational access. A series of wave screens at regular intervals along the inner wall of the breakwater provides an opportu-nity to flush the water into the canal (to improve water quality) and breaks up the regularity of the caisson structure.

Nielsen said while the design is wider than a conventional breakwater, the ca-nal itself offers a number of alternative uses, including an artificial reef habitat that could offer snorkelling and diving opportunities, as well as water-sport op-portunities such as kayaking and dragon boating. ■

Nielsen described the numerical wave fl ume as the computer-based equivalent of a traditional scale-model physical wave fl ume.

A model of the proposed marina in Hong Kong.

Australian modelling

used for marina design


COVER STORY


Tunnel and vortex shafts to stop fl oodingby Gabriel TO Woo

S urface runoff is a critical challenge in densely urbanised Hong Kong, but a new stormwater intercep-

tion tunnel will alleviate the concerns of the residents of Tsuen Wan and Kwai Chung Districts regarding flooding.

Situated along the shoreline of the Rambler Channel in Hong Kong, the densely populated urban districts of Tsuen Wan and Kwai Chung were not prepared

for the chest-deep torrent that inundated the area in 1997, following exceptionally intense rainfall.

Runoff from surrounding catchments entered local streams and quickly ran down the slopes that surround the town. The stormwater drainage system of the Tsuen Wan and Kwai Chung Districts (surface drainage channels and under-ground pipelines) that was built over 30

years ago was capable of dealing with routine storms but didn’t have the spare capacity to handle the additional storm-water arising from the rapid urbanisation of the towns. In the event of exceptional deluge it was overwhelmed, resulting in flooding in many areas of Tsuen Wan and Kwai Chung. When the 1997 floodwaters receded, they left a trail of destruction in its wake.

Now, thanks to a new A$190 million stormwater drainage tunnel, constructed by joint venture contractor Maeda-CRGL-SELI with construction overseen by Mott MacDonald Hong Kong, any repeat of that situation will be avoided. Flow from three major local rivers will be diverted at mid-hill to a 5km long tunnel through vertical intake shafts and then diverted westwards at a depth of up to 200m below ground level. The tunnel bypasses the town and discharges directly to the sea. The system effectively creates a defensive line above Tsuen Wan and Kwai Chung Districts that will protect the towns against flooding from rainfall events with return periods of up to 50 years.

The circular profile tunnel has a mini-mum internal diameter of 6.5m, with a 250mm-thick prefabricated reinforced concrete segmental lining. The tunnel can carry up to 223kL/s of water. A double-shield tunnel boring machine (TBM) excavated the tunnel in hard intact rock formations that included crystal ash tuff, basalt, rhyolite, granite and quartz, and lengths of heavily-faulted ground. Tunnel-ling commenced in April 2010, starting at the shoreline outfall in the west. The TBM worked up-gradient in a general easterly direction passing through two intake shaft locations and terminating at the eastern intake shaft in Upper Kwai Chung.

The TBM passed close to existing wa-ter and railway tunnels, as well as below extensive surface installations including water treatment works and reservoirs. The installation of comprehensive geo-technical instrumentation and careful construction sequencing ensured that any disturbance of these facilities was kept to a minimum.

The three intake structures were con-

The new stormwater drainage tunnel can carry up to 223kL/s of water. It was completed in March.


COVER STORY


structed to depths of 20m to 40m below ground using mechanical and chemical drill-and-split techniques in open-cut and drill-and-blast cavern excavation. The intake structures include innovative reinforced concrete spiral vortex shafts to streamline the incoming flow.

“The slope on the spirals is gentle, so the water runs down through the drop shaft into the tunnel in a smooth, controlled stream,” Mott MacDonald Hong Kong managing director KM Yeung said. “That prevents pockets of air from being forced into the tunnel, which could cause water to back up and

overtop the approach channels.”Physical modelling was used to deter-

mine the layout and dimensions of the intakes, as well as to perfect the pitch and width of the vortex spirals. The largest of spiral vortices has a diameter of 16m, which connects to a drop shaft of 30m.

The system is passive, with the inter-ception of flow during intense rainstorms controlled by weirs on the intakes, which have scope for manual adjustment if necessary. The weir levels are designed to operate and divert flow into the intakes when rainfall intensity exceeds 30mm/h, which is classified by the Hong Kong

Observatory (the Hong Kong govern-ment’s meteorological service), as an “amber” rainstorm.

The tunnel outfall structure at Yau Kom Tau comprises four 9m-wide re-inforced concrete cells with an internal height of 4.5m, which are enclosed and covered with a landscaping deck fitted with planter troughs. It is an energy dissipation device which is designed to receive the flow from the tunnel and condition it for final discharge to the sea. From the tunnel portal, a tapered channel of increasing width, with baffles, leads to a stepped cascade spillway. This connects to a box culvert conveying the flow under the dual carriageway Castle Peak Road and through another series of baffles discharging to an outfall basin on the sea bed.

The tunnel was commissioned in March and will no doubt prove its worth in the years to come.

The new tunnel means that runoff from the surrounding hills can now be dealt with before it reaches the urban area, and has enabled the government to avoid extensive and disruptive road works to enlarge the town’s existing drainage infrastructure.

“Hopefully the tunnel won’t be often needed,” Yeung said. “But when the next big storm arrives, Tsuen Wan and Kwai Chung will be ready.” ■

Gabriel TO Woo is chief engineer/consultants management of the Drainage Services Department of the government of the Hong Kong Special Administrative Region and a member of Engineers Australia.

Main partiesClient: The Drainage Services De-partment of the government of the Hong Kong Special Administrative Region.Consultant: Mott MacDonald Hong Kong, including conceptual design, detailed design and construction supervision.Contractor: Maeda-CRGL-SELI, including detailed design of tun-nel lining and immediate intake structures.


Intake structures were constructed to depths of 20m to 40m below ground using mechanical and chemical drill-and-split techniques, and connected to a TBM bored drainage tunnel.


COVER STORY

Engineers Australia | May 2013 47Engineers Australia | May 2013 47

Unique building creatinga new design hub

A spiring to become one of Asia’s leading design hubs, a futuristic tower has risen on the campus of

Hong Kong Polytechnic University – the first piece of permanent architecture in Hong Kong by world-renowned architect Zaha Hadid.

Construction work began on the 15-storey Jockey Club Innovation Tower in 2009 and the whole project is expected to be completed by midyear. Upon completion, the Innovation Tower will accommodate 1700 students and 100 staff, and will house the School of De-sign, the newly established Jockey Club Design Institute for Social Innovation, various studios and labs, a museum and a public gallery.

Arup has performed the role of struc-tural and building services engineer.

BIM (building information modelling) has been an integral component in the design and construction of this three dimensionally irregular building. Arup said it has proved particularly useful for carrying out clash analysis with building elements and services, as well as provid-ing an efficient mode of communication between the architectural, structural, building services and façade engineers.

“The façade is one of the key elements of this building. Weekly design workshops were often focused on the verification of design information provided by the architect against BIM information built from the onsite surveying of the structural elements, building services and façade structures,” Arup director Kin-Kei Kwan said. “BIM frequently highlighted design issues which would have been impossible for either the consultants or contractor to detect using traditional graphical projec-tion drawings.”

Arup also used design software in Etabs to carry out the structural analysis. With the coordinates from the Etabs model, the engineers produced a struc-tural outline using Revit to communicate with the architect’s Rhino model.

The structural engineering design challenges of the tower included the tower overhanging the footpath on the north and tilting forward, with foundations not permitted in the path. In response, Arup designed the superstructure to use three main cores and beam-column frames for lateral load and eccentric tower loads. Raking columns are used in some areas to handle the tilting tower, which was placing very large overturning forces on

the structure. Discrete transfer beams have been used on the third floor to free up the lower two levels.

With a unique building geometry, Kwan said that to achieve the architect’s intent for the curved three-dimensional façade, several alternative cladding materials were investigated including fibre-reinforced plastic and aluminium.

Ultimately, the building profile called for unique curved three-dimensional metal cladding. The key façade design challenge on the project was the detailing and interface resolution of the cladding, Kwan said. This feature was particularly challenging as there was minimal repeti-tion and the fixing positions changed at each floor level.

It was also realised that due to the projection of the façade cladding, some glass could not be reached by the build-ing maintenance unit’s normal operation. To come up with a workable solution, a series of catwalks was designed behind the feature cladding with removable ac-cess panels to the interior. The panels are located in spaces which can be safely closed by facilities management staff while the building is open. ■

The tilting Innovation Tower of Hong Kong Polytechnic University is set to become the design hub for the region when it opens in the coming months. The building has been designed by world-renowned architect Zaha Hadid, while Arup is performing the role of structural and building services engineer.

PHOTO: ARUP


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