The 360m long Access Gallery meets the machine Hall and
the Transformer Hall at their eastern ends. The excavation of the modified
horseshoe shape gallery was performed by perimeter drilling to achieve a
regular rock surface, suited to final shotcrete. Mesh support and
mechanically anchored rockbolts, 3.5m long with 100KN capacity, were used
on fractural material. A total excavation of 26 500m³ was required,
including a lateral channel for the pipes and cables and the 18m
extensions between the Machine caverns and Transformer Hall.
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