Gotthard Base Tunnel - Comparison of forecast and findings regarding engineering geology and tunnelling / Gotthard-Basistunnel - Vergleich Prognose und Befund aus baugeologischer und tunnelbautechnischer Sicht
|Issue:||Geomechanics and Tunnelling", 2016, n. 3, v. 9|
For deep tunnels with restricted possibilities for site investigation, deviations from the forecast are usually to be expected. Deviations of geological and hydrogeological conditions have different effects on tunnelling. At the Gotthard Base Tunnel it was found that some areas considered as critical actually behaved most favourably, whereas other areas, such as fault zones and zones of high rock pressure, deviated unfavourably from the forecast with considerable effects on costs and the time schedule. Unfavourable deviations could not be compensated by favourable areas. It should be also noted that these deviations had not been included in risk analyses, because they were unknown, however the original cost prognosis of 1999 provided sufficient financial reserves. These deviations were mastered by intensive probing ahead of excavation and adaptation of design, construction programme and additional measures defined during construction. On the basis of the comparison of forecast and actual conditions, the positive and negative effects of the conditions encountered on tunnelling are described.
|Keywords:||deep seated tunnel - tiefliegende Tunnel, prognosis - Prognose, Befund - actual conditions, engineering geology - Baugeologie, tunnel driving technique - Tunnelbautechnik|
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