TKO-LTT Interchange and Associated WorksEnhancing connectivity of Tseung Kwan O with East Kowloon

Winning over design challenges

Designing the interchange was not an easy feat. Challenges included designing and constructing the seven bridges over the marine zone that pose aggressive environmental conditions. Some of the project complexities included:

• Heavy wave actions, onshore wind and water seepage
• Highly curved road geometry alignments
• Precast segmental single box deck
• Balanced cantilever construction method
• Narrow deck with complex structural details

Accurate assessments of exposure severity were vital to determine appropriate approaches with sufficient durability. According to the requirement, the bridges were designed and built for a design life of 120 years. To ensure the structure remains resilient to the extreme natural events, the piles for the bridges were founded in competent rock with some pile lengths exceeding 50 m.

With the bridges constructed over the sea, the geological longitudinal section of the rock goes as deep as 50 m below sea level requiring longer piles, while the bridge piers have piles cantilevering reaching to 20 m from the seabed. The team at Aurecon considered the method of erection, ensuring the geometry of the bridge superstructures met the required tolerances.

Geometry control work included the development of segment casting geometry, provision of segment data for individual segment match casting work at the precast yard and on-site erection geometry control work during segment erection. Aurecon also worked closely with the contractor to avoid step joints between the T-spans.

The bridges have extreme tight curvature with radii as low as 44 m, the geometric behaviour of the bridges is more complicated than straight bridges with inherent challenges. To address this, the project team avoided using external post-tensioning but adopted internal tendons. This approach saved the cost of erecting closely spaced deviators and resulted in better constructability.

Safety as the primary concern throughout the project

To successfully construct the precast segmental bridges in the marine zone with minimal disturbance to the natural environment, while providing design solutions for the works to be carried out safely, was also a challenge.

Aurecon strived to integrate safety in both the design and construction phases to ensure that workers were protected against any unnecessary exposure of potentially unsafe matters. This initiative also helps to reduce the amount of future maintenance works by enhancing the durability of the permanent works. Measures taken included:

• Adopting precast shells to enhance work safety and reduce disturbance to the environment
• Fulfilling the crack width limits on the pile cap shell to enhance durability; this helps reduce long term repair work and maintenance requirement at sea
• Utilising modularisation to minimise manual works in the sea
• Adopting a simpler method of shell installation and integration with permanent works
• Deploying Aurecon’s in-house digital experts and developed 3D geometrical models for plate element analysis for clash detection and better determinations of design actions

This project is one of two contracts that Aurecon was enjoyed for as part of Tseung Kwan O – Lam Tin Tunnel (TKO-LTT). The other is the tunnel and associated works that connects to the interchange. Together, these two projects are a vital part of forming a new strategic route network for the citizens of Hong Kong.