Awardees: Ir Leung Chung Lap Michael and Ir Tsang Hing Kai Ivan

The Tseung Kwan O - Lam Tin Tunnel constitutes a new trunk road for the Tseung Kwan O Development. A 2.2-km main tunnel connects Kowloon East at the Lam Tin Interchange (Figure 1) and a branch tunnel channels traffic directly to the Eastern Harbour Crossing. The new road is also the eastern section of the future Route 6 that will serve as an express link between Kowloon East and West.

Figure 1: The Lam Tin interchange

The project encompasses a number of notable features. The rock cavern of the tunnel bifurcation section excavated using drilling and blasting has a 38m span, the longest ever in Hong Kong (Figure 2). Emergency provisions for the 700m branch tunnel, a single tube precluding the conventional cross-passage arrangement, are in the form of a specialdesign pressurised evacuation corridor. Between the main and branch tunnels, a 42m ventilation adit at 45º incline was installed to reduce head loss, thereby enhancing energy efficiency of the tunnel ventilation and smoke extraction system.

Figure 2: The main tunnel and the branch tunnel

Construction of the tunnel posed numerous challenges, including blasting in close proximity with operating MTR lines at only 12m clearance. State-of-the-art blasting design and technologies were applied to control ground movement and vibration. In addition, mining the branch tunnel underneath the artery Lei Yue Mun Road and underground utilities with just 3m cover from road level called for complicated installation, then subsequent removal, of a robust traffic deck with precise pipe roofing and lattice girders to ensure works and traffic safety.

Sustainability was a key consideration throughout project implementation. From the planning stage, the project team kept optimising the tunnel alignment and extent of reclamation on the Tseung Kwan O side. In tandem with delivering the free-flow tolling system that eliminated the need for a toll plaza, they reduced the scale of reclamation by 70%. This minimised the tunnel length to 2.2 km. Treated marine sediment from the reclamation was re-used on site. To suppress construction impact as far as possible, for the first time in Hong Kong a double water gate was installed during reclamation to strengthen protection against water pollution.

Another innovation was locating the east ventilation building partially in caverns straddling the carriageways. This led to a smaller footprint and significantly reduced rock excavation and slope stabilisation works at the steep terrain of the Tseung Kwan O portal. This helped to preserve the natural green cover on the hillside. In addition, the project applied the “single site, multiple use” concept to turn a landscaped deck, being functioned as an effective noise mitigation measures, into the Tseung Lam Highway Garden, which serves as a public space hub enriching the amenity of the promenade cycling loop.

Most noteworthy is that the project was completed during extremely challenging times. Through perseverance, steadfastness, dynamicity and collaborative team spirit, the project team comprising the Civil Engineering and Development Department, AECOM, contractors and subcontractors overcame various unprecedented technical and non-technical difficulties.

The new tunnel has brought about significant traffic benefits to Tseung Kwan O and its environs, shortening the journey time to Kowloon East by 20 minutes during morning peak hours. The notable infrastructural improvement is closely related to people’s livelihood and enhances their sense of blissfulness as well as promotes the continuous development of Tseung Kwan O.