Central Kowloon route, Hong Kong

The Central Kowloon Route (CKR) will ease congestion in the most densely populated area of Hong Kong, reducing the time commuters spend stuck in traffic during the daily morning and evening rush hours.

For communities living near major roads, stop-start traffic reduces air quality, damaging people’s health and their quality of life. Alternative routes below ground can free up existing surface roads and improve the environment for nearby communities.

The CKR is a 4.7km, three-lane dual carriageway linking areas in Hong Kong’s Kowloon peninsula. It will provide an alternative east-west express route to relieve congestion, and includes almost 4km of tunnels. Mott MacDonald is providing design, engineering and construction supervision services in a joint venture with Arup (AMMJV).

Opportunity

Minimising surface changes and disruption to Hong Kong’s existing infrastructure and communities are key considerations. Congested construction and tunnelling areas are affected by the presence of utility networks and roads that need to remain open wherever possible. The Kowloon peninsula has been expanded through land reclamation and its geology is complex. Seven potential fault zones lie along the central area of the CKR route: excess groundwater inflow could cause ground settlement and pose safety risks. Several vital public facilities are also located along the route, including six reservoirs, Queen Elizabeth Hospital, a gasworks and four in-service railway tunnels.

A 390m cut-and-cover tunnel will run beneath Yau Ma Tei district at the southern end of Kowloon. It will have a 40m span and be 35m below ground at its deepest point. At its nearest point, excavation will take place just 3m from existing buildings. Most of the 2.7km central tunnel – spanning between 17m and 21m – will be constructed using the drill and blast method (DBM), which provides the flexibility necessary to the tunnel’s geometry. The construction programme is tight, with all work having to be completed in just four years.

Solution

Sequencing of construction work for the cut-and-cover tunnel is being carefully monitored and managed. Noise barriers and enclosures have been erected to minimise disruption to the local community and allow 24/7 working. Diaphragm walls will provide temporary support for excavation and, eventually, a permanent tunnel side wall. Ground and building settlement analysis was carried out to ensure buildings close to the excavation will not be affected, while jet grouting and land-based deep cement mixing is being used to strengthen the ground and protect surrounding structures and utilities.

A waterproofing layer and geotextile membrane will be installed in each of the seven fault zones affecting the central tunnel. This will cover the entire perimeter of the tunnel lining, which is designed to take the full groundwater pressure. Sensors have been installed along the route, and vibration from DBM excavation is being strictly controlled. An impact assessment tested the structural integrity of public facilities and other structures along the route, and a non-blasting zone will protect the most sensitive structures. It normally takes at least a year to get a blasting permit from the Hong Kong authorities, but we secured one in just five months to allow work to commence.

Outcome

This comprehensive range of rigorous measures and precautions aided initiation of the CKR and will keep Hong Kong safe and moving throughout its construction, which is due to be completed in 2025. This new highway is essential to the future of one of the world’s major cities. It will help to keep traffic flowing and take congestion away from surface roads. This will be vital to maintaining Hong Kong’s position as a global economic hub and it will also benefit its 7.5M residents – 2M of whom live in Kowloon, making it the city’s most populous area.

Taking traffic off surface roads will improve air quality and reduce the potential for accidents, especially those involving pedestrians. This will improve health, safety and wellbeing. It will also return to many commuters those five days spent in traffic jams every year!