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Geological 3D Model of the Investigation Niche in ONKALO, Olkiluoto, Southwestern Finland

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Geological 3D Model of the Investigation Niche in ONKALO, Olkiluoto, Southwestern Finland Working Report 2014-35 Geological 3D Model of the Investigation Niche in ONKALO, Olkiluoto, Southwestern Finland Noora Koittola Posiva Oy July 2014 Working Reports contain information on work in progress or pending completion. ABSTRACT The main goal of this Master of Science Thesis was to create a geological 3D-model of the investigation niche 3 and its surroundings. The model were created for the needs of the rock mechanical back analysis. This study is a part of Posiva's regional studies for characterization of the bedrock. Totally 4 models were created: lithological model, foliation model, fracture model, and physical rock property model. Besides the modeling, there was also made a study of the migmatite structures in the niche. Used geological and geophysical methods were drill core loggings, tunnel mapping, ground penetration radar, mise-á-la-masse and drill hole geophysics. Four rock types exist at the niche area: veined gneiss, pegmatite granite, diatexitic gneiss and quartz gneiss. The lithological units were modeled primary with the drill core loggings, tunnel mapping and ground penetrating radar. The major lithological units followed the main foliation direction (south dipping). So the continuations were fairly easy to model in the walls and roof, where the data was lacking. Foliation and fractures were modeled as discs, with mid-points at the measurement points of the structure. There were two main foliation directions 164/46 and 62/39. Fractures were more scattered but three fracture sets can be separated: 156/34, 270/85 and 342/83. The first set is mainly from the drill core loggings, second and third from tunnel mapping. Used methods in foliation model were drill core loggings, tunnel mapping and drill hole geophysics. In fracture model used data was from drill core loggings, tunnel mapping, mise-á-la-masse measurements and drill core geophysic. Four anomalous zones were detected with the drill hole geophysics. Three of these zones were associated with intensely fractured zones and one was connected to exceptionally high mica content in the gneiss. Rocks of Olkiluoto are divided into gneisses and magmatic rocks in the geological mapping. Actually almost all Olkiluoto's rocks are more or less migmatites. The migmatite classification is created at the moment so it was reasonable also study the migmatite structures. The recognized structures were schlieren, homophanous, veined and the border of metatexite and diatexite. Besides the modeling, there was also made a quality control of the used data and methods. During the modeling was also located a slickenside fracture set under the niche. There is a possibility that this fracture set is connected to one of the brittle fault zones (bfz-265). Despite this, these structures cannot be combined before additional studies. Keywords: Olkiluoto, ONKALO, final disposal of nuclear waste, Surpac, 3D-model, structural geology, geophysics, rock mechanic, POSE experiment, back analysis, lithology, foliation, fracture, anomaly, migmatite, quality inspection, bfz-265. Geologinen 3D malli ONKALO:n tutkimuskuprikasta 3, Olkiluodossa TIIVISTELMÄ Tutkimuksessa luotiin 3D-malli tutkimuskuprikka 3:sta ja sen lähialueen geologiasta. Mallit luotiin erityisesti kalliomekaanisen takaisinlaskennan tarpeisiin. Tutkimus toimii- kin osana Posiva Oy:n aluetutkimuksia, joiden tavoitteena on karakterisoida Olkiluodon kallioperää. Malleja luotiin yhteensä 4 kappaletta: litologiamalli, foliaatiomalli, rakoi- lumalli ja malli kiven fysikaalisista ominaisuuksista. Mallinnuksen lisäksi kuprikasta tehtiin migmatiittirakenteiden tutkimus. Mallinnuksessa käytettyjä geologisia ja geofy- sikaalisia metodeja olivat kairasydänloggaukset, tunnelikartoitus, maatutkaus, lataus- potentiaalimittaukset ja kairareikägeofysiikka. Litologiamalliin mallinnettiin solideina kuprikan alueella esiintyneet neljä kivilajia: suonigneissi, pegmatiittigraniitti, diateksiittinen gneissi ja kvartsigneissi. Yksiköt mal- linnettiin ensisijaisesti kairasydänloggausten, tunnelikartoituksen ja maatutkausten avul- la. Suurimmat kivilajiyksiköt seurasivat vallitsevaa foliaatiosuuntaa (etelään kaatuva), joten jatkeita oli helppo mallintaa myös kattoon ja seiniin, joista data oli puutteellista. Foliaatio ja rakoilu mallinnettiin disc-tasoina, joiden keskipiste sijaitsee rakenteen mit- tauspisteessä. Foliaatiosuuntia ilmeni kaksi: 164/46 ja 62/39. Rakoilu oli epäsäännölli- sempää, mutta kolme päärakosuuntaa erottui: 156/34, 270/85 ja 342/83. Näistä ensim- mäinen on määritelty lähinnä kairasydänloggauksista ja kaksi viimeistä ovat tunnelikar- toituksesta. Foliaatiomallin luonnissa käytettiin dataa kairasydänloggauksista, tunneli- kartoituksesta ja kairareikägeofysiikasta. Rakoilumalli luotiin loggausten, kartoituksen, latauspotentiaalin ja reikägeofysiikan avulla. Reikägeofysiikassa havaittiin neljä fysikaalisesti anomaalista vyöhykettä kuprikan alta. Näistä kolme liittyi ensisijaisesti intensiivisesti rakoilleeseen gneissiin ja yksi gneissin poikkeuksellisen korkeaan kiillepitoisuuteen. Olkiluodon kivilajit jaotellaan kartoituksessa ja mallinnuksessa gneisseihin ja syväki- viin. Todellisuudessa Olkiluodon kivet ovat kaikki enemmän tai vähemmän migmatiit- teja. Parhaillaan ollaan luomassa alueen migmatiittirakenneluokittelua, joten tähänkin työhön otettiin mukaan myös kuprikan migmatiittien tarkastelu. Kuprikasta löytyneet rakenteet olivat suurimmaksi osaksi eriasteisia schlieren -rakenteita. Kuprikan alueelta löydettiin myös homofaaninen rakenne, suonirakenne sekä metateksiittisen ja diatek- siittisen migmatiitin raja. Mallinnuksen lisäksi työssä haluttiin keskittyä käytetyn datan ja luotujen mallien laatutarkasteluun sekä niiden käytettävyyden arviointiin. Mallinnuksen aikana löydettiin kuprikan alta myös intensiivisesti rakoillut haarniskarakosetti, joka viittaa mahdolli- suuteen, että kuprikan alla kulkee hauraan ruhjevyöhykkeen (bfz-265) jatke. Näiden rakenteiden yhdistäminen tarvitsee kuitenkin vielä lisätutkimuksia. Asiasanat: Olkiluoto, ONKALO, ydinjätteen loppusijoitus, Surpac, 3D-mallinnus, rakennegeologia, geofysiikka, kalliomekaniikka, POSE-koe, takaisinlaskenta, litologia, foliaatio, rakoilu, anomalia, migmatiitti, laatutarkastelu, bfz-265. 1 CONTENTS 1. INTRODUCTION ............................................................................................ 3 2. REGIONAL GEOLOGY .................................................................................. 5 2.1. Geology of southern Finland .................................................................... 5 2.1.1. Tectonic Evolution .............................................................................. 7 2.2 Geology of Satakunta Area ....................................................................... 8 2.3 Geology of Olkiluoto Island ..................................................................... 11 2.3.1 Lithological Classification used in Geological Mapping ..................... 11 2.3.2 Migmatite Classification .................................................................... 11 2.3.3 Deformation and Metamorphism ....................................................... 14 3. THIRD INVESTIGATION NICHE .................................................................. 17 3.1 Excavation History .................................................................................. 17 3.2 POSE Experiment ................................................................................... 19 4. DATA AND METHODS ................................................................................ 23 4.1 Geological Methods ................................................................................ 23 4.1.1 Drill Core Loggings ........................................................................... 23 4.1.2 Geological Mapping of the Niche and Experiment Holes .................. 24 4.2 Geophysical Methods .............................................................................. 27 4.2.1 Ground Penetrating Radar ................................................................ 27 4.2.2 Mise-á-la-Masse Surveys ................................................................. 30 4.2.3 Drill Hole Geophysics ........................................................................ 33 4.3 3D-modeling Methods ............................................................................. 35 5. RESULTS ..................................................................................................... 37 5.1 Lithological Model ................................................................................... 37 5.1.1 Modeled mica bands ......................................................................... 43 5.2 Foliation Model ........................................................................................ 44 5.3 Fracture Model ........................................................................................ 47 5.4 Physical Rock Property Model ................................................................ 48 5.5 Modeling Files ......................................................................................... 49 5.6 Migmatite Structures in the Investigation Niche ...................................... 49 6. DISCUSSION ............................................................................................... 55 6.1 Applicability and Representativeness of the Data and Methods ............. 55 6.2 Representativeness of the Model ............................................................ 56 6.3 Correlation with the Site Model ..............................................................
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