Strength, Deformation And Seismic Response Of Olkiluoto Migmatitic Gneiss Under Laboratory True-Triaxial Stress

M.H.B. Nasseri, Mahdi Sehizadeh, Sheng Hua Ye, Paul Young, J. William Flynn, Johannes Suikkanen, Topias Siren

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Abstract

A unique set of true-triaxial experiments have been used to mimic the loading path that the in situ rock is
exposed to during excavation, heating, cooling and unloading through the Posiva’s Olkiluoto Spalling Experiment
(POSE), at the proposed deep geological repository at Olkiluoto, Finland. Results from testing of rock specimens
prepared with their foliation planes oriented with respect to σ1, under true-triaxial conditions, show that 0o, 30o
and 60o gneiss samples fail whereas 90o gneiss and isotropic pegmatite specimens do not fail under the same
loading path. The pegmatite specimen shows numerous acoustic emission (AE) activities but does not fail during
the final stages of the stress path. Temporal and spatial analysis of AE events show that fracture initiation and
propagation are sensitive to foliation plane orientation with respect to σ1 and that failure planes coincide with
foliation planes in failed specimens. Variation of seismic wave velocities measured along three orthogonal axes
as a function of the loading path show that compressional and shear wave velocities measured parallel to
foliation planes are higher than perpendicular to such planes characterizing the transversely isotropic nature of
Olkiluoto gneiss. The true-triaxial POSE experimental loading and unloading path is complex and results in
strength and behavioural characteristics that are not replicated with conventional triaxial testing where σ2 = σ3.
Original languageEnglish
Title of host publication7th International Symposium on In-Situ Rock Stress
Subtitle of host publicationSymposium Proceedings
EditorsErik Johansson, Ville Raasakka
Place of PublicationTampere, Finland
PublisherSuomen rakennusinsinöörien liitto RIL
ISBN (Electronic)978-951-758-606-1
Publication statusPublished - 11 May 2016
MoE publication typeA4 Article in a conference publication
EventInternational Symposium on In-Situ Rock Stress - Tampere Hall, Tampere, Finland
Duration: 10 May 201612 May 2016
Conference number: 7
http://www.ril.fi/en/events/rs2016/home.html

Publication series

NameRIL
PublisherSuomen rakennusinsinöörien liitto RIL
ISSN (Electronic)0356-9403

Conference

ConferenceInternational Symposium on In-Situ Rock Stress
Abbreviated titleRS2016 Symposium
Country/TerritoryFinland
CityTampere
Period10/05/201612/05/2016
Internet address

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