Comparison of dfn modelled microfracture systems with petrophysical data in excavation damaged zone
2021 (English)In: Applied Sciences, E-ISSN 2076-3417, Vol. 11, no 7, article id 2899Article in journal (Refereed) Published
Abstract [en]
Physical and petrographic properties of drill core specimens were determined as a part of investigations into excavation damage in the dedicated study area in the ONKALO® research facility in Olkiluoto, Western Finland. Microfractures in 16 specimens from two drillholes were analysed and used as a basis for fractal geometry-based discrete fracture network (DFN) modelling. It was concluded that the difference in resistivity between pegmatoid granite (PGR) and veined gneiss (VGN) specimens of similar porosity was likely due to differences in the types of microfractures. This hypothesis was confirmed from microfracture analysis and simulation: fractures in gneiss were short and mostly in one preferred orientation, whereas the fractures in granite were longer and had two preferred orientations. This may be due to microstructure differences of the rock types or could suggests that gneiss and granite may suffer different types of excavation damage. No dependencies on depth from the excavated surface were observed in the geometric parameters of the microfractures. This suggests that the excavation damaged zone cannot be identified based on the changes in the parameters of the microfracture networks, and that the disturbed layer observed by geophysical methods may be caused by macro-scale fractures. © 2021 by the authors.
Place, publisher, year, edition, pages
MDPI AG , 2021. Vol. 11, no 7, article id 2899
Keywords [en]
Discrete fracture network model, Excavation damage, Laboratory testing, Percolation cluster, Petrophysics, Physical properties of rocks, Simulation
National Category
Other Civil Engineering
Identifiers
URN: urn:nbn:se:ri:diva-52968DOI: 10.3390/app11072899Scopus ID: 2-s2.0-85103849565OAI: oai:DiVA.org:ri-52968DiVA, id: diva2:1547424
Note
Funding details: Suomen Akatemia, 319798; Funding text 1: This research is based on work funded by Posiva Oy. This research was funded by the Academy of Finland, grant number 319798.
2021-04-262021-04-262023-05-25Bibliographically approved