The Guangzhou-Shenzhen-Hong Kong express rail line links these three large Chinese cities with trains travelling at up to 300 kilometres/hour. For this project, the Dragages Hong Kong and Bouygues Travaux Publics joint venture blast-excavated an approximately 3-kilometre-long single tube tunnel (contract 821). A 3.5-kilometre twin-tube tunnel was also built using two tunnel boring machines for the section between Mei Lai Road and Hoi Ting Road (contract 820). A special feature of contract 821: a largesized cavern where the junction tunnel meets the main tunnel.