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

Quarzite with slate inclusions
uniaxial strength approx. 80 MPa - 120 MPa
Eilrig Shear Zone with highly destabilized zones
(the collapse of the TBM tunnel took place in this zone)

General data

Glendoe Recovery Project
construction of a bypass tunnel around a collapse area
an access tunnel to the headrace tunnel
repair works in the headrace and tailrace tunnel

Scottish Southern Energy (SSE)

Wayss & Freytag Ingenieurbau AG
in a joint venture

Construction period
January 2010 to March 2012

Construction costs
€ 68 million

Bypass Tunnel
605 m
Construction Method
drill and blast method in combination with tunnel excavator
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