KYT KARIKKO (Kallioperän Rikkonaisuus/Bedrock fracturing) KYT2022-SAFIR2022 Interim Seminar - Nicklas Nordbäck (Geological Survey of Finland)
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KYT KARIKKO
(Kallioperän Rikkonaisuus/Bedrock fracturing)
KYT2022-SAFIR2022 Interim Seminar
Nicklas Nordbäck
(Geological Survey of Finland)
Role of brittle structures 2
Conceptual Model of an aquifer system in fractured, crystalline rock. Colorado Geological Tunneling of the geological nuclear waste repository in Olkiluoto, Finland.
Survey (2003).
• Brittle structures play an important role in the suitability of bedrock
volumes for different underground applications.
• Conventional underground construction where bedrock stability needs to be assessed
• Advanced application, such as construction of deep geological nuclear waste
repositories where pathways for groundwater flow needs to be assessed in more
detail.
9.4.2021
KYT KARIKKO project goals: 3
• Estimate bedrock fracturing and fracture properties at different scales by means of large-scale
lineament interpretations, drone-photogrammetry and modelling
• Develop new methods for collection and analysis of large fracture and lineament datasets
• By increasing the availability of data and advanced methods for data-analysis, our aim is to limit
current levels of uncertainty associated to e.g. DFN, hydrogeological and 3D models
• In addition, we asses the possibilities to incorporate other geological information and interpretation
in estimating the properties of fracturing. E.g. conceptual geological models, hydrogeology and rock
mechanics.
• Our datasets enables a broader comparison between e.g. the fracturing in Olkiluoto and the
broader regional fracturing patterns and properties. Our results and goals are also useful for other
societial needs where bedrock stability and groudwater flow needs to be understood (e.g.
groudwater resources, geothermal energy etc.).
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3D/DFN MODELLING OF FRACTURE NETWORKS
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Fracture parameters for modelling
• Orientation, intensity, length distributions
Drone fracture data LiDAR lineaments and topology
• Data is required in multiple scales
• Time consuming mapping of small
structures, uncertainty regarding larger
ones. Restricted size of outcrops -> Largest
structures only partly or not visible ->
lineament interpretations
• Scaling of fractures • Uncertainty of lineament interpretations
(foliation, ice age etc.)
DFN model
• 100 m – 1km scale structures are usually
difficult to map even as lineaments
• Assumptions between different scales e.g.
length vs. intensity → uncertainties of DFN
models
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Generalised geological map of south-western Finland. The locations of Inkoo, Helsinki and Olkiluoto are highlighted with black stars.
LINEAMENT DATA Source data for lineament interpretations, visualized for the Inkoo 1:200k area.
Figure visualising the
different map scale areas,
the interpreted lineament
datasets (A-C) and the UAV
fracture data (D).
Cumulative number
Length
Multi-scale power law plot
DRONE FRACTURE DATA 8
• Workflow for gathering (drone based) and analysing fracture data (python based) is under
development. Fractopo-2D: https://github.com/nialov
• Automated fracture mapping methods tested and developed in cooperation with PET-keskus and
Aalto (RAKKA).
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FRACTURE PARAMETERS Orientation
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Length distribution
• Parameters of the fracture network
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FRACTURE PARAMETERS 10 • P21 -> Intensity of the fracture network and spatial variations 9.4.2021
FRACTURE PARAMETERS 11 • Topology -> Connectivity of the fracture network and spatial variations 9.4.2021
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KARIKKO research areas 2019-2020
1:200 000 lineament interpretations
Loviisa
Inkoo
Ahvenanmaa
Pro Gradu: Ovaskainen, N., 2020.
Pro gradu in prep: Kraatz., Scalability of lineament and fracture
S. Structural geological networks within the crystalline Wiborg
investigations on brittle Rapakivi Batholith, SE Finland
structures, eastern Åland Publication in prep: Nordbäck et al. Multi-
scale characterisation of fracture networks,
2-3 publications in Inkoo, Southern Finland Journal of Structural Geology: Skyttä et
planning phase al. 2021. Fault-induced mechanical
Publication in prep: Libby et al. Grown DFN anisotropy and its effects on fracture
modelling paper. patterns in crystalline
9.4.2021 rocksGETA - LONG FRACTURES
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• Scalability of mode I fractures,
single mode II fractures and small
9.4.2021 fault zones.SUMMARY
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• KYT KARIKKO has developed new methods for mapping and analysing brittle structures
• Development to be continued 2021-2022
• KYT KARIKKO has collected a large structural geological database from southern Finland
• To be extended during 2021
• Uncertainties related to modelling can be mitigated by undertanding:
• Data uncertainties and limitations
• The tectonic history of the bedrock and its effect on the development of brittle structures
• Mechanisms affecting the geometry of structures
• Scalability of brittle structures
• Topological properties of brittle structures
• Publication work
• Two PhD projects started
• One approved research article (Journal of structural geology, accepted January 2021) and four other research articles in
prep. (international publications during 2021-2022).
• One pro gradu finalised at the beginning of 2020 and another aiming to be finalised by the end of 2021.
• Results have been presented at several international conferences (pre-corona).
9.4.2021Thank you!
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