Vol 22 No 2 (10-2012)
Reconstruction and Improvement of Tuen Mun Road (II) – Tai Lam Section (HY/2007/10)


Reconstruction and Improvement of
Tuen Mun Road (II) –
Tai Lam Section (HY/2007/10)

Background

Reconstruction and Improvement of Tuen Mun Road is divided into 3 sections, namely, Sam Shing Hui Section, Tai Lam Section and Eastern Section. In our previous issue we have published the article on the Sam Shing Hui Section, in this issue we continue to introduce the Tai Lam Section .

The Contract

The contract of Reconstruction and Improvement of Tuen Mun Road – Tai Lam Section is numbered HY/2007/10. The contract sum is HK$1.328billion and the main contractor is China State Construction Engineering (Hong Kong) Limited. The project commenced in February 2009, and is expected to be completed in end 2014.

The Tai Lam Section of Tuen Mun Road is a 4 kilometres long dual 3-lane carriageway connecting Tsing Lung Tau and Siu Lam. In order to upgrade the Tuen Mun Road to the current expressway standards as far as possible, the scope of works includes, inter alia, widening traffic lanes to expressway standards, provision of hard shoulders, upgrading the road conditions (with better sightlines, gradients, cross falls in curves, radii of alignments), improvement of the merging or diverging lanes at Siu Lam Interchange, widening vehicular bridges (including Tai Lam Bridge and Brother’s Bridge), extending pedestrian subways, installing noise barriers, and replacement of the existing road restraint system etc. Upon completion of the above upgrading works, it is expected that the safety of road users in Tuen Mun Road can be enhanced.

The construction time for the works in the contract is approximately six years. Slope works, filling works and construction of retaining walls are being done in the earlier stage while road reconstruction works will be carried out subsequently. The contract is now in its peak period with more than 200 workers.

Widening of
Tai Lam Bridge

Widening of Tai Lam Bridge is one of the important works in the Reconstruction and Improvement of Tuen Mun Road. After building the abutments of the Tai Lam Bridge, a temporary steel working platform is erected to provide working space for installing piles and for pier construction. The precast beams between the piers or abutment are firstly fabricated in mainland, and are shipped to Tai Lam Bridge directly. Upon delivery on site, derrick barge is deployed to install the bridge beams between piers or abutment. The bridge deck is cast in-situ, with the new bridge deck and the existing bridge deck stitched together to form a widened bridge finally.

Slope Cutting Works

Along both sides of Tuen Mun Road, there are a large number slopes. In order to create adequate space for widening the traffic lanes, it is necessary to carry out further cutting to set back the existing slopes. In the Tai Lam section, the majority of the slope cutting works are in the proximity of Tsing Lung Tau Bridge on Tuen Mun bound side of the Tuen Mun Road. The volume of earthworks arisen from slope cutting works is approximately 58,000 m3. To safeguard the road users and the workers, the Contractor has to erect safety fences and rock-fall fences along the roadside of Tuen Mun Road before the commencement of slope cutting works so as to prevent boulders falling onto the adjoining traffic lanes. Besides, the Contractor has to form a temporary construction access road to link the slope toe and the slope crest so as to facilitate the transportation of construction equipment for the slope cutting works. When the uppermost batter is formed, surface drains are then constructed on the newly formed slope to prevent the finished slope surfaces from being eroded by rainwater. This process is then repeated for the lower batters until the whole slope is completely formed.

Reinforced Earth Wall

In the Tai Lam section of Tuen Mun Road, a number of reinforced earth walls (RE Wall) are built so as to create space for widening the traffic lanes. The longest RE Wall in Tai Lam section is built along Castle Peak Road near Tai Lam Chung area.

In the Tai Lam section, most of the RE Walls are built on the slopes off Tuen Mun bound lanes of Tuen Mun Road. Under the circumstances, construction accesses for the RE Walls have to be connected to Castle Peak Road. In order to create adequate space for construction of the RE Walls, the Contractor has to construct temporary cut slopes with temporary soil nails. The RE Wall has to be built layer-by-layer, with the excavation work firstly carried out for the base level, followed by placement of a layer of drainage filter. After the in-situ footings are cast for sitting the bottom row of the precast concrete facing panels, ribbed tie-strips are installed at the backside. Later on, the facing panels are tied back in a layer-by-layer fashion up to the required wall height. Precast copings and safety handrails are eventually installed at the top of the finished RE Wall.

Improvement of Sight Lines

The curvature of the horizontal alignment of Tuen Mun Road near Tsing Lung Bridge at the eastern end of Tai Lam Section is not desirable, and this may affect the visibility of motorists. In view of this, improvements to the horizontal alignment of this section of Tuen Mun Road are carried out. Upon completion of the improvements, sightlines of the motorists will be extended with better visibility and traffic safety will be enhanced in this road section.

Improvement of
Siu Lam Interchange

To cope with the widening of the Tuen Mun Road, the Contractor has to modify the existing alignments of the merging/ diverging lanes at Siu Lam Intechange, with reconstruction or relocation of the affected kerbline, traffic signs, concrete profile barriers, anti-crash beams and traffic lighting etc. Upon completion, the merging/diverging lanes at the interchange will be widened, and this helps improve the sightlines of the motorists.

Removing the Separation Zones at Median

At some sections of the Tuen Mun Road, there exist level difference between the east bound lanes and west bound lanes. As such, central separation zones have to be provided at the median. In the Tai Lam section, the lanes in concerned road sections will be widened by removing the central separation zones.

Construction Equipment

Since Tai Lam section involves installation of many precast beams in bridge widening works, a crane with 500-tons lifting capacity is deployed to facilitate the widening works for the Tai Lam Bridge and the Brother’s Bridge. In addition, a standby crane with 250-tons lifting capacity can be mobilized when necessary.

Challenges

Widening of Tai Lam Bridge is one of the important works in the Reconstruction and Improvement of Tuen Mun Road. The Contractor has to carry out marine works including piling operation and bridge piers construction. However, piling operation may affect the marine environment and the ecology therein. In addition, in the waters below the Tai Lam Bridge, there is an important submarine watermain which supplies water to the Chek Lap Kok Airport. In order to ensure that the water supply to the airport is not disrupted, it is necessary for the Contractor to adopt appropriate piling method and to deploy suitable types of construction equipment so as to avoid damaging the submarine watermain. Besides, movements of the submarine watermain are closely monitored so as to prevent excessive vibrations and settlement. Moreover, as required by the Water Supplies Department, piling operation can only be carried out in wet seasons. This imposes significant difficulty for widening the Tai Lam Bridge.


Construction time is also limited. Despite the construction period for the Tai Lam section spans over approximately six years, it takes more than two years to complete slope cutting works. Extensive and stringent temporary traffic arrangements have to be implemented during the contract period so as to maintain the normal traffic service, and with the objective of causing the least disruption to the public as far as practically possible. As required by the Government, all traffic lanes should remain open for daytime, especially throughout the peak hours and no construction works are allowed at the peak hours. As a result, temporary lane closures with limited extent can only be implemented in non-busy hours, usually in midnight time. As such, the contractor can only divide road widening works into multi-stages. These constraints impose great pressure for completing the works within the specified construction duration.

The topography of Tuen Mun Road, being bound by natural terrain or cut slopes alongside, also poses a great challenge for the Contractor. Materials delivery to the construction sites could only be carried out through closed traffic lanes under limitation. Since there is no appropriate access along the slopes of both sides, the Contractor has to construct accesses from Castle Peak Road to facilitate the construction.

During the construction period, the diversion of traffic lanes and construction vehicles may not only cause inconvenience to the road users, but also may lead to traffic accidents. To ensure road safety, when construction vehicles deliver materials into the construction sites, a shadow vehicle with flashing lights is arranged for escort and to alert the motorists to slow down. Temporary variable message sign system is also used to alert the motorists for road safety message, traffic news and hotline contact.

Environmental Protection

Throughout the construction period, the Contractor has to exercise great efforts in protecting the environment so as to mitigate the impacts due to the construction as far as practically possible.

One of the efforts is to re-use the surplus earthworks and rocks generated from slope cutting. According to the construction waste management measures as stipulated by the Government, the surplus earthworks and rock materials should be disposed of to designated fill bank. In order to minimize any unnecessary disposal of the surplus earthworks and rocks off site, most of these materials are delivered to the adjacent sites for re-use.

Besides, noise screens are temporarily installed at appropriate positions adjacent Hong Kong Garden to mitigate the noise impacts arisen from the construction works, which are mainly carried out during midnight time or early morning. In addition, low noise plants are used, and muffling devices are installed on the equipment which generates significant noise with the objective of mitigating the noise impacts on the nearby residents as far as practically possible.

Community Liaison

To enable the public to better understand the details and progress of the project, Highways Department has set up a Community Liaison Centre at Sam Shing Hui in Tuen Mun in July 2010, with staff answering public enquiries in connection with the project. Information related to the project will also be made available to the public by display boards, models and video slides. A 24-hour telephone hotline is also set up by the contractor to address enquiries and complaints of the public.

Progress and Conclusion

The reconstruction works of Tuen Mun Road Tai Lam section are in good progress. Foundation works of noise barriers at central median near Hong Kong Garden, road reconstruction near Tai Lam Kok and Ka Lung Tsuen and construction of baffle wall near Choi Yuen Tsuen are now in progress. Upon completion of the reconstruction and improvement of Tuen Mun Road, the traffic conditions of the road will be improved and safety will be enhanced.





Courtesy acknowledgement:
Highways Department
Major Works Project Management Office
for providing the above information and photos

We would like to express our appreciation to
Ir. Dr. Wong Chung-kwong Sam
Chief Engineer
Major Works Project Management Office -
Highways Department
for the valuable information and support he provided during the preparation of this featuring article.