Trenchless construction of Phase IIIA District Cooling System (DCS) by TBM pipejacking and hand-dug tunnelling on Kai Tak Development : Part II – The challenges

This paper discusses the challenges of constructing 1.75 km of concrete sleeve pipelines with diameters of 1,200mm, 1,500mm and 2,800mm using slurry operated Tunnel Boring Machines (TBMs) for installing District Cooling System (DCS) pipelines in highly variable ground conditions within the Kowloon Bay area. It covers the problems encountered, solutions provided, and recommendations made. Various construction techniques are also discussed including: running two TBMs in parallel from a jacking pit for the near simultaneous construction of two pipelines; enlarging the lower section of a receiving pit by the caving method to receive the TBM which entered the pit at an oblique angle, for turning inside the pit for removal after skin-off of the TBM; construction of a hand-dug tunnel from a receiving pit to receive three TBMs one at a time in a triangular configuration to suit site constraints. This paper should be read together with Part I which is entitled “Design and Construction Considerations” published in 2017.