|
Markus Vaarma, Geological Survey of Finland (Finland)
Meri-Liisa Airo, Geological Survey of Finland (Finland)
Tuija Elminen, Geological Survey of Finland (Finland)
Piri Harju, Poyry Intra Oy (Finland)
Matti Pajunen, Geological Survey of Finland (Finland)
Pekka Wasenius, Geological Survey of Finland (Finland)
Marit Wennerström, Geological Survey of Finland (Finland)
|
|
The technical properties of bedrock are a function of the geological evolution, particularly the structural and tectono - thermal history, that the crust has gone through. The technical properties of rock masses are the main concern in planning, constructing, and exploiting the bedrock for the needs of communities particularly as underground spaces become increasingly indispensable in urban areas.
Understanding the geological framework of bedrock within a target area planned to be exploited will help estimate the suitability and risks in different civil engineering purposes. Three research projects of the Geological Survey of Finland (GTK) ongoing since 1999, predominantly in the Helsinki Capital region, have been focused on the lithology, ductile and semi-brittle to brittle faulting and jointing structures to reconcile how the technical properties of rock masses and the geological history of the local bedrock are linked. The main goal was to identify and classify zones of weakness within the study area, and estimate the control of the 1.9 - 1.8 Ga Svecofennian ductile tectonics on these structures and the pattern and frequency of jointing in these rock masses. Investigations revealed a network of zones of weakness mostly due to brittle deformation which splits the area into blocks with rather consistent internal features and jointing trends that account for the technical properties of rock masses. The results are presented as construction suitability maps with explanatory reports.
The data received from previous underground construction targets of local authorities, and especially observations made by GTK in the Savio railway tunnel during its excavation in 2005 - 2006 will be invaluable when evaluating and enhancing the relevance of the information received from field observations and processed topographical and aerogeophysical maps. The Western extension of the Helsinki Subway System is in the elaboration stage and intensive studies of bedrock have already utilized the results and experiences acquired in the above mentioned research projects of GTK.
|
