China State Construction Engineering Corporation (CSCEC) has completed excavation of Sri Lanka’sUpper Elahera Canal Water Diversion Tunnel.
Two TBMs manufactured by China Railway Construction Heavy Industry Corporation (CRCHI) broke through from opposite directions to complete boring on the 27.7 km tunnel – the longest water diversion tunnel currently under construction in South Asia and the core of Sri Lanka’s North Central Province Canal Project (NCPCP).
During excavation, the TBMs encountered multiple geological challenges, including hard rock strata, water-bearing fractured zones, and shallow overburden sections.
To address these challenges, CRCHI designed two 7.6m-diameter double shield TBMs with a dual-support system combining segmental lining and rock bolting with shotcrete. The machines were also equipped with a high-strength, wear-resistant rock excavation system and a long-life main drive, enabling continuous long-distance tunnelling without intermediate access shafts.
CRCHI says the TBMs set a single-heading drive record of 17km.
During construction, the two machines consistently maintained equipment availability of more than 95 per cent. The maximum monthly advance by a single TBM was 808m, while the two machines achieved a monthly advance of more than1,313m.
To mitigate a restricted jobsite space, CRCHI’s technical team provided on-site services from the project planning phase, providing power supply solutions, gantry layouts, material logistics, and split-launch methodologies. Three split-launch operations were completed, enabling the TBMs to maintain continuous excavation.
Once completed, the tunnel will provide a water corridor from south-central Sri Lanka to the drought-prone northern regions, providing water to 73,800ha of farmland and 375,000 households.
