Comparison between preinvestigations and detailed geotechnical site characterization of City Link, Stockholm.
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
A statistical comparison between the pre-investigations and the detailed site characterization while tunneling was performed in three areas of different rock quality in the Södermalm’s Tunnel. An overview of the site investigations performed prior to the construction works and the consequences in the tunneling method are also presented in this study.
The statistical analyses in this study showed low correlation within the results obtained from the geotechnical investigations performed prior and while tunneling. The correlation diminishes as the rock mass quality decreases; however, in areas where the rock mass quality is high, the correlation is not as elevated as expected. The low association within those results may be due to diverse factors: the concentration of the pre-investigations in mostly three areas along the trace of the tunnel, and the extension of those results to the rest of the tunnel; the inappropriate utilization of the investigation techniques; and the lack of geotechnical data in the regional areas of Stockholm.
The inaccurate geological characterization given by the pre-investigations leaded to great challenges in the most fractured and altered areas of the tunnel. A collapse occurred where the glaciofluvial sediments were in contact with the rock. The excavation had to be stopped and additional rock reinforcement had to be applied. Therefore, an increase of the expenses in terms of time and budget were the major consequences of the inaccurate predictions.
Place, publisher, year, edition, pages
, TRITA-LWR Degree Project, ISSN 1651-064X ; 2012:26
pre-investigations; RMR; Q; rock reinforcement; glaciofluvial
IdentifiersURN: urn:nbn:se:kth:diva-171800OAI: oai:DiVA.org:kth-171800DiVA: diva2:844539
Olofsson, Bo, professor