Christoph Huber’s presentation will explore the challenges and innovative solutions associated with the application of New Austrian Tunnelling Method in hyperbaric atmosphere during the con-struction of Tunnel Karl-Friedrich-Strasse in Karlsruhe (Germany).
The project – Shortlisted for NCE Tunnelling Festival’s ‘Innovation in Tunnel Excavation’ award – posed a unique challenge with its small overburden (approximately 7m), a poor geol-ogy consisting of gravel, sand and fine sand and layers of rolling gravel.
Given the tunnel’s variable geometry (of up-to 180m² tunnel face; 15 m diameter), NATM was chosen as the preferred excavation method. However, due to the inner-city location and a very high water table, the excavation had to be carried out in a hyperbaric atmosphere, of circa 1.0 bar, which created special challenges for the application of wet mix shotcrete. Other challenges included: air losses and the corresponding air flow, and the presence of his-toric buildings along the path of the excavation (including a 125y old brick lined sewer directly above the tunnel alignment).
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