Gammon Construction illustrated its devotion in enhancing construction technologies by the completion of the deepest tunnel for the Harbour Area Treatment Scheme (HATS) and installation of the mega-size precast unit for the Central-Wanchai Bypass project. The innovative technology not just marks a new milestone for the underwater tunnel construction, but also fosters a safer and greener working environment.

 

The sewage system (from North Point to Stonecutters Island) of HATS Stage 2A project successfully achieved breakthrough of Hong Kong’s deepest tunnel, with its depth up to 160m below sea level. It was also the longest and deepest sewage tunnel constructed by drill and blast method in Hong Kong.

 

To ensure a smooth working progress and the safety of the workers, Gammon Construction has applied a number of innovative solutions and information technology to strengthen the risk and safety management, including:

 

·Tunnel personnel tracking system by the use of RFID, complemented with CCTV monitoring system for real time monitoring of the tunnel situation to enhance work safety.

 

·Automatic Shaft Mucking System introduced from Australia to reduce manual procedures and workers’ working time in tunnel, resulted in higher efficiency and improved safety.

 

·3D laser scanning to check the excavation profile to increase the accuracy and save working time.

 

·Apart from using of walkie-talkie and phone system for daily communication, Wi-Fi network was set up in the tunnel. Tablet with anti-shake and dust-proof functions was used for instant communication with staff on the ground, such as sending photos and documents. As a result, working procedures were streamlined and time was saved.

 

Several green measures were also adopted, including the use of fully enclosed noise enclosure, LED lighting to save energy and reduce carbon emission, chiller system to provide dry and comfortable working environment, deploying electrical power run for most of the tunnel plants and using extra low sulfur diesel for locomotives.

Installation of Precast Concrete Unit

 

Gammon-Leader Joint Venture has successfully installed a mega-size precast concrete unit above the MTR Tsuen Wan Line tunnel for the Central-Wanchai Bypass project. In order to avoid any adverse effect caused to the MTR Tsuen Wan Line, 51 bored piles in two rows were constructed along both sides of the MTR tunnel to support the precast unit.

 

The precast unit was cast from five individual concrete units. It measures 125m in length, 48m in width, 12m in height, and 46,000 tonnes in weight and was transported by sea. The combination of the original 5 units reduced the impact to the harbour users by eliminating the transportation to one time. It also enables a more stable floating state during installation.

 

During the construction of piles, the Joint Venture constructed a large working platform with precast structure. This could streamline the works on the water surface and underwater, it also reduced the use of barges and vessels in the busy waters of Victoria Harbour. It was the first time for the construction team to use Hydraulic Sheetpile follower to mitigate the environmental impact, such as reduction of vibration and the impact to MTR Tsuen Wan Line, as well as noise impact to neighbourhood as a result of less works at night. In addition, mechanical and hydraulic tools were used to cut and trim the pile head concrete so that less manual works were needed to be carried out under sea level.

 

Real Time Kinematics (RTK) GPS technology was applied to provide real time data in achieving precise accuracy when the unit landed on the bored piles.

 

Gammon Construction will continue to introduce and apply advanced engineering technology to provide a more efficient, safer and greener way for the increasingly complex projects.

 

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Candy Chan                   

Corporate Communications Manager

Tel: + 852 2516 8733

Email: candy.chan@gammonconstruction.com