Client: K.T.B.
Location and Year: Wellawaya, Sri Lanka, 2014-2015
Features: TBM Bored Tunnel
Project description

In Wellawaya, Sri Lanka, a TBM bored tunnel was constructed for a hydroelectric powerplant in the Uma Oya Multipurpose Development Project.
The tailrace tunnel, with a length of 3,5 kilometers and a diameter of 4 meters, diverts water from the Uma Oya to the powerplant 700 meters below surface level, which will deliver over 230 GWh annually.
The tunnel was bored with a 162 meter long Double Shield TBM which simultaneously placed the concrete segments for the lining.


Arthe has been asked by contractor K.T.B. to consider different aspects of the boring process, including:

  • Site engineering
  • Mapping the geology of the route
  • Risk assessment
  • Monitoring and improving daily progress:
    • Placement of lining segments
    • Backfilling
    • Analysis of dug out soil
    • Predicting upcoming geology
    • Test drillings