Technical specifications

Scope of work

• Bypass tunnel, 605 m,
  excavated cross-section: 28 m², as a D-shaped profile
  with a gradient of 12%
  access via existing headrace tunnel
  (length: 2 km, 19 m² circular cross-section, 12% gradient);
• Access tunnel, 550 m,
  Excavated cross-section 28 m², as a D-shaped profile;
  exploration borings from above ground to detect cavities in the rock;
  shotcrete inner linings in the bypass tunnel and in places in the headrace tunnel;
  partial removal of the flushed out collapse material from the headrace tunnel;
  closing of the collapse area and the access tunnel by means of a concrete seal

Construction method

• Mining techniques:
  drill and blast method in combination with tunnel excavator
  and sprayed concrete lining (SCL),
• Classification of tunnelling operations according to the Q-System,
• Advance per round: 1.5 m - 4 m

Geology