Faults in crystalline rock and the estimation of their mechanical properties at the Olkiluoto site, western Finland

• Published in: Engineering geology Vol. 117; no. 3; pp. 246 - 258
• Main Authors: Hudson, John A., Cosgrove, John W., Kemppainen, Kimmo, Johansson, Erik
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 02.02.2011; Elsevier
• Subjects: Applied sciences; Brittle deformation zone; Brittleness; Buildings. Public works; Deformation; Ductile brittle transition; Engineering design; Exact sciences and technology; Fault; Faults; Finland; Geology; Geotechnics; Mechanical properties; Pollution; Radioactive waste repository; Radioactive wastes; Rock; Rock mechanics; Site investigation; Soil investigations. Testing; Soil mechanics. Rocks mechanics; Wastes; Europe; Finland; Brittle deformation zone; Radioactive waste repository; Fault; Rock mechanics; Finland; Site investigation; Radioactive waste; Deformation; Site analysis; Mechanical properties; Brittle material; Spoil dump; Classification; Example; Crystalline rocks
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2010.11.004

Brittle deformation zones at the Olkiluoto nuclear repository site in western Finland play critical roles in the strength and hydrology of the host rock mass. We present a procedure implemented there for incorporating information on deformation zones obtained through boreholes into quantitative engineering design. First, ductile and brittle deformation zones are classified based on their characteristics in drillhole cores as brittle joint clusters, brittle fault zones, or semi-brittle fault zones, with an awareness of the geologic processes that caused the zones to develop as they did. Next, it is shown that the mechanical properties of the brittle deformation zones can be calculated by one of several methods, each of which has advantages and disadvantages. The site geology must be kept in mind at all stages to arrive at meaningful estimates of the mechanical properties of the deformation zones. ► Structural geology provides important support for rock engineering design. ► Brittle and ductile deformation zones are examined and illustrated. ► An integrated structural geology-rock mechanics engineering approach is described.