Core Drilling of Shallow Drillholes OL-PP72...OL-PP89 at Olkiluoto, Eurajoki 2011

Working Report 2012-20

Core Drilling of Shallow Drillholes OL-PP72...OL-PP89 at Olkiluoto, Eurajoki 2011 Vesa Toropainen

May 2012

POSIVA OY FI-27160 OLKILUOTO, FINLAND Tel +358-2-8372 31 Fax +358-2-8372 3709

Working Report 2012-20

Core Drilling of Shallow Drillholes OL-PP72...OL-PP89 at Olkiluoto, Eurajoki 2011 Vesa Toropainen Suomen Malmi Oy

May 2012

Working Reports contain information on work in progress or pending completion.

The conclusions and viewpoints presented in the report are those of author(s) and do not necessarily coincide with those of Posiva.

CORE DRILLING OF SHALLOW DRILLHOLES OL-PP72...OL-PP89 AT OLKILUOTO, EURAJOKI 2011 ABSTRACT Suomen Malmi Oy (Smoy) core drilled eighteen drillholes to survey the ground and bedrock conditions in the encapsulation plant building site at Olkiluoto, Eurajoki 2011. Soil quality, bedrock depth and quality of near surface bedrock were investigated in this project. The drillholes were drilled between 19th of October and 8th of November 2011. The lengths of the drillholes are mostly between 7 to 9 metres, except for the drillhole OL-PP79, which is 15 metres by length. The drillholes are 76 mm by diameter, and the core diameter is 60.2 mm. The lightweight GM75 drilling rig with rubber tracks was used. The drilling water was taken from the ONKALO area research building freshwater pipeline and sodium fluorescein was added as a label agent in the drilling water. The drillholes were not left open. In addition to drilling the drillcores were logged and reported by geologist. Geological logging included the following parameters: lithology, foliation, fracture parameters, fractured zones, core loss, weathering, fracture frequency, RQD and rock quality. The average natural fracture frequencies of the drillcores range from 2.5 pc/m (OLPP77) to 11.8 pc/m (OL-PP86). The average RQD ranges from 55.1 % (OL-PP86) to 96.4 % (OL-PP77). The penetrated soils are mostly ground fill (blast rock), but some clays and sands are lying below the fill layer. Keywords: Olkiluoto, ONKALO, encapsulation plant, core drilling, drillhole, diatexitic gneiss, soil quality.

MATALIEN KAIRAREIKIEN OL-PP72...89 KAIRAUS OLKILUODOSSA, EURAJOELLA VUONNA 2011 TIIVISTELMÄ Suomen Malmi Oy (Smoy) kairasi kahdeksantoista matalaa kairareikää kapselointilaitoksen pohjatutkimuksia varten Eurajoen Olkiluodossa vuonna 2011. Reikien tarkoitus oli antaa tietoa maapeitteen paksuudesta ja laadusta sekä pinnanläheisestä kallioperästä. Reiät kairattiin 19. lokakuuta ja 8. marraskuuta 2011 välisenä aikana. Reikien pituudet vaihtelevat noin seitsemästä yhdeksään metriin, lukuun ottamatta reikää OL-PP79 joka on noin 15 metriä pitkä. Reikien halkaisija on 76 mm ja näytteen halkaisija 60,2 mm. Reiän kairaustyössä käytettiin kevyttä kumiteloilla liikkuvaa kairauskonetta GM75. Reiän kairaukseen käytettiin ONKALO-alueen tutkimushallin vesilinjasta otettua vettä, joka merkittiin natriumfluoresiinilla. Kairareikiä ei jätetty auki. Kairatuille kallionäytteille tehtiin geologinen kartoitus ja raportointi, joka sisälsi mm. kivilajit, suuntautuneisuuden, rakoparametrit, rakotiheyden ja RQD:n, rikkonaisuusvyöhykkeet, muuttuneisuuden, näytehukan ja kivilaadun. Pääkivilajeina rei'issä esiintyy diateksiittinen gneissi. Kallion rakoluku rei'issä vaihteli 2,5:stä (OL-PP77) 11,8:aan (OL-PP86) ja vastaavasti RQD samoissa rei'issä 55,1 %:sta 96,4 %:iin. Havaittu maapeite alueella koostui pääosin täytemaasta (louhemurska), mutta sen alla oli paikoin hiekkaa ja savea. Avainsanat: Olkiluoto, ONKALO, kapselointilaitos, kairaus, kairareikä, diateksiittinen gneissi, maapeite.

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TABLE OF CONTENTS ABSTRACT TIIVISTELMÄ 1

INTRODUCTION ................................................................................................ 3 1.1 Background ............................................................................................. 3 1.2 Scope of the work .................................................................................... 3

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DRILLING OF SHALLOW DRILLHOLES OL-PP72...OL-PP89 .......................... 5 2.1 Schedule of the drilling work.................................................................... 5 2.2 Description of the drilling work................................................................. 5 2.3 Drilling water and the use of label agent ................................................. 5 2.4 Locations of the drillholes ........................................................................ 5 2.5 Soil quality observations .......................................................................... 6

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GEOLOGICAL LOGGING................................................................................... 7 3.1 General .................................................................................................... 7 3.2 Core orientation ....................................................................................... 7 3.3 Lithology .................................................................................................. 7 3.4 Foliation ................................................................................................... 8 3.5 Fracturing ................................................................................................ 9 3.6 Fracture frequency and RQD ................................................................ 13 3.7 Fractured zones and core loss .............................................................. 14 3.8 Weathering ............................................................................................ 15 3.9 Core discing........................................................................................... 15

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ROCK MECHANICS ......................................................................................... 17 4.1 The rock quality ..................................................................................... 17

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SUMMARY........................................................................................................ 19

REFERENCES ............................................................................................................. 21 APPENDICES 1 Technical details of the drillholes ........................................................... 23 2 Soil quality observations ........................................................................ 27 3 Core boxes ............................................................................................ 31 4 Core lifts ................................................................................................ 35 5 Lithology ................................................................................................ 39 6 Foliation ................................................................................................. 43 7 Fractures ............................................................................................... 49 8 Fracture frequency and RQD ................................................................ 69 9 Fractured zones and core loss .............................................................. 73 10 Weathering ............................................................................................ 77 11 Q'-classification ..................................................................................... 81 CORE PHOTOGRAPHS .............................................................................................. 85

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1 1.1

INTRODUCTION Background

Posiva Oy submitted an application to the Finnish Government in May 1999 for the Decision in Principle to choose Olkiluoto in the municipality of Eurajoki as the site of the final disposal facility for spent nuclear fuel. The Government made a positive decision at the end of 2000. The Finnish Parliament ratified the decision in May 2001. The policy decision makes it possible to concentrate the research activities at Olkiluoto in Eurajoki. One part of the research is to build an underground rock characterisation facility (called “ONKALO”). ONKALO will be used to obtain information for planning the repository and to assess the safety and constructing engineering solutions. ONKALO will also enable the final disposal technology to be tested under actual conditions. Construction of the access tunnel ONKALO started in 2004. The encapsulation plant will be constructed above ONKALO facility. To investigate the thickness and quality of the overburden and the quality of the near-surface bedrock at the building site, Posiva Oy contracted (order numbers 9453-11 and 9789-11) Suomen Malmi Oy (Smoy) to drill 18 shallow drillholes (OL-PP72...OL-PP89). 1.2

Scope of the work

The aim of the work was to drill 18 vertical shallow drillholes (OL-PP72...OL-PP89), observe the thickness and quality of the overburden and to drillcore samples of bedrock. The lengths of the shallow drillholes (from 6.80 to 8.95 metres) were planned so, that they will reach depth level +0.0 m. However, one of the drillholes (OL-PP79) is located at the position where the canister shaft will be constructed (Figure 1). The length of the drillhole OL-PP79 is 15.03 metres. In addition to the drilling of the holes, the work included geological logging of the core samples and also reporting. This report documents the work done during drilling the holes and geological core logging of the shallow drillholes. Geological logging was done by geologists Vesa Toropainen and Jarmo Kuusirati. Compilation of the final report was done by Vesa Toropainen.

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Figure 1. The locations of the shallow drillholes OL-PP72...89 in ONKALO area, Olkiluoto. Black outline and circle represent the encapsulation plant and shaft.

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2 2.1

DRILLING OF SHALLOW DRILLHOLES OL-PP72...OL-PP89 Schedule of the drilling work

The drilling of the shallow drillholes took place in autumn 2011. The drilling started at the first drillhole OL-PP79 on the 19th of October 2011 and the last drillhole OL-PP76 was finished on the 8th of November 2011. The drillholes were not drilled in numerical order. 2.2

Description of the drilling work

The drilling rig used in the work was a lightweight multipurpose GM-75 rig on rubber tracks. The drilling team in one shift consisted of a driller and an assistant. The drilling started by penetrating the overburden with a temporary steel casing tube (¡ 99/78 mm) and drilling it (¡ 99 mm bit size) to the surface of the bedrock. The holes were then further drilled with T76 equipment to the final drillhole depths. The steel casing tube was lifted up after the drilling of each drillhole. Therefore the drillholes were not left open. Drillhole nominal diameter with T76-core barrel is 76 mm and drillcore diameter is 62.0 mm. Technical information of the drillholes is presented in Appendix 1. The soil quality was recorded during casing drilling (Appendix 2). The drillcore samples were placed in wooden core boxes immediately after emptying the core barrel. The number of core boxes for each drillholes are presented in Appendix 1 and the start and end depths of the core in each core box are listed in Appendix 3. Wooden blocks separating the different lifts were placed to the core boxes to show the depth of each lift. The depths of the lifts are presented in Appendix 4. 2.3

Drilling water and the use of label agent

The water for drilling the holes and flushing was taken from the ONKALO fresh water pipeline. All drilling water was marked with the label agent sodium fluorescein. The sodium fluorescein solution was delivered by Posiva. At the TVO Olkiluoto laboratory, the sodium fluorescein was dissolved in water in 5 litre bottles. The sodium fluorescein is an organic powdery pigment, which is dispersed by UV radiation. Therefore, the label agent mixing bottles were covered. At the drilling site, dose of 10 ml of solution was taken with syringe and mixed for each cubic metre of water (the planned concentration is 250 μg/l). The pre-mixed solution was slowly added into the mixing tank at the beginning of pumping. Turbulence caused by pumping water into the tank ensured proper mixing of the label agent. 2.4

Locations of the drillholes

Location surveys were conducted 9.9. and 23.11.2011 by Prismarit Oy (Table 1, Figure 1). The locations of the drillholes were surveyed beforehand and no significant move from the planned locations of the drillholes were necessary, except for drillholes OL-PP76, 77 and 85. Their realized locations were surveyed also after drilling.

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Table 1. Surveyed coordinates, lengths and levels of the shallow drillholes. Drillhole OL-PP72 OL-PP73 OL-PP74 OL-PP75 OL-PP76 OL-PP77 OL-PP78 OL-PP79 OL-PP80 OL-PP81 OL-PP82 OL-PP83 OL-PP84 OL-PP85 OL-PP86 OL-PP87 OL-PP88 OL-PP89

2.5

X 6792014.83 6792020.76 6792028.99 6792035.08 6792041.87 6792051.65 6792024.07 6792032.89 6792039.51 6792047.83 6792053.38 6792066.31 6792043.60 6792055.38 6792055.44 6792073.48 6792079.88 6792085.01

Y 1525852.87 1525866.02 1525884.14 1525897.87 1525910.88 1525922.89 1525852.37 1525870.19 1525859.15 1525889.30 1525905.94 1525921.89 1525838.27 1525847.08 1525866.26 1525873.03 1525887.13 1525900.82

Z 7.85 7.98 8.04 8.74 8.62 8.84 6.76 7.74 7.54 7.93 8.26 8.68 6.34 6.54 7.05 7.54 7.32 7.76

Z bedrock surface 3.00 5.98 7.49 8.04 8.22 7.94 3.81 6.74 5.49 6.78 7.76 7.88 1.94 3.84 4.90 3.21 5.10 4.88

Drillhole length, m 7.85 8.08 8.05 8.60 8.90 8.85 6.80 15.03 7.55 7.95 8.23 8.75 6.50 7.30 7.05 7.60 7.38 7.80

Z Drillhole end 0.00 -0.10 -0.01 0.14 -0.28 -0.01 -0.04 -7.29 -0.01 -0.02 0.03 -0.07 -0.16 -0.76 0.00 -0.06 -0.06 -0.04

Soil quality observations

The soil quality was observed during overburden drilling by the driller. The observations are based on the drillbit advance, drilling sound and upcoming drill cuttings and flushed soil material. The change depth of soil quality was recorded. The soil at surface was mostly earth fill (probably blast rock) in most of the drillholes. On some drilholes till, gravel, fine sand, silt and clays were peneterated below the fill layer. The soil quality observations are shown in Appendix 2.

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3 3.1

GEOLOGICAL LOGGING General

The handling of the core was based on the POSIVA work instructions POS-001427 ”Core handling procedure with triple tube coring” (in Finnish). Drillcore samples were placed into about one-metre long wooden core boxes immediately after emptying the core barrel. The drillcore was handled carefully during and after the drilling. The core was placed in the boxes avoiding any unnecessary breakage. If loose rock fragments from the drillhole walls were encountered during the logging, they were placed after the block marking the end of the previous sample run. Therefore, at the beginning of a sample run, there might be rock fragments not belonging to the sample run itself. Geologists Vesa Toropainen and Jarmo Kuusirati logged the cores in Posiva’s core logging facility at ONKALO site. The core logging of the drillcores followed the normal Posiva logging procedure, which has been used e.g. in pilot hole drilling programmes at Olkiluoto. The following parameters were logged: lithology, foliation, fracture parameters, fractured zones, weathering, core loss, artificial break, fracture frequency, RQD, rock quality and core discing. In addition, the lifts and the core box numbers were documented. All core boxes (Appendix 3) were digitally colour photographed, both dry and wet. The core photographs (wet) are presented at the end of the report. The lift depths (Appendix 4) are given as they were marked on the wooden spacing blocks separating different sample runs in the core boxes. If the length of the core in the sample run indicated that sampling depth was different from the depth measured during drilling, the true sample depth was corrected on the spacing block. Therefore, the sample run depth equals the sample depth. The drilling depth might be deeper than the sampling depth, if the core lifter slips and part of the core is left in the drillhole and is retrieved by the next lift. The measured true sample depths were marked to the core sample with short red lines perpendicular to the core direction in one metre interval. Those depth values were marked to the upper dividing wall of the core box row. The logging results of the eighteen drillholes are discussed mainly as a whole, not by drillhole, as they are very closely spaced and can be considered as random samples of the same rock mass. Spatial variations are discussed if they were found. Some special attention is placed on the drillhole OL-PP79 (canister shaft hole). 3.2

Core orientation

Core orientation was not carried out in vertical drillholes. 3.3

Lithology

The rocks of Olkiluoto fall into four main groups: 1) gneisses, 2) migmatitic gneisses, 3) TGG-gneisses (TGG = tonalite-granodiorite-granite) and 4) pegmatitic granites (Kärki & Paulamäki 2006). In addition, narrow diabase dykes occur sporadically. The gneisses

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include homogeneous mica-bearing quartz gneisses, banded mica gneisses and hornblende or pyroxene-bearing mafic gneisses. The migmatitic gneisses, which typically contain 20 – 40 % leucosome, can be divided into three subgroups in terms of their migmatite structures: veined gneisses, stromatic gneisses and diatexitic gneisses. The leucosomes of the veined gneisses show vein-like, more or less elongated traces with some features similar to augen structures. Planar leucosome layers characterize the stromatic gneisses, whereas the migmatite structure of the diatexitic gneisses is asymmetric and irregular. The lithological classification used in the mapping follows the classification by Mattila (2006). In this classification, the migmatitic metamorphic gneisses are divided into veined gneisses (VGN), stromatic gneisses (SGN) and diatexitic gneisses (DGN). The percentage of the leucosome proportion in gneisses is reported. The non-migmatitic metamorphic gneisses are separated into mica gneisses (MGN), mafic gneisses (MFGN), quartz gneisses (QGN) and tonalitic-granodioritic-granitic gneisses (TGG). The metamorphic rocks form a compositional series that can be separated by rock texture and the proportion of neosome. Igneous rock names used in the classification are coarse-grained pegmatitic granite (PGR), K-feldspar porphyry (KFP) and diabase (DB). The TGG gneisses are medium-grained, relatively homogeneous rocks that can show a blastomylonitic foliation, but they can also resemble plutonic, unfoliated rocks. The pegmatitic granites are leucocratic, very coarse-grained rocks, which may contain large garnet, tourmaline and cordierite crystals. Mica gneiss enclaves are typical within the larger pegmatitic bodies. Gneisses, which are weakly or not at all migmatitic, make ca. 9 % of the bedrock. The migmatitic gneisses comprise over 64 % of the volume of the Olkiluoto bedrock, with the veined gneisses accounting for 43 %, the stromatic gneisses for 0.4 % and the diatexitic gneisses for 21 %, based on drillcore logging. Of the remaining lithologies, the TGG-gneisses constitute 8 % and the pegmatitic granites almost 20 % by volume (Kärki & Paulamäki 2006). Most of the samples OL-PP72...89 consist of diatexitic gneiss (85.73 m, 77.0 %). It is mainly weakly banded or irregular by foliation and contains usually 60 - 70 % leucosome material. The leucosome granite is commonly reddish coloured. The pegmatitic granite, logged as separate lithologies when exceeding drillhole length of 1 m comprises 9.3 % of the core samples (10.63 m). The PGR is coarse grained, massive and has reddish coloured K-feldspar. It includes small amounts of cordierite. The veined gneiss (10.40 m, 9.3 %) and mica gneiss (4.53 m, 4.1 %) make up the rest of the sample length. The veined gneiss is weakly to moderately banded with commonly reddish leucosome veins. Locally inside the migmatitic gneisses there are also short, mainly gneissic and fine grained low leucosome sections, logged as mica gneiss (Appendix 5). 3.4

Foliation

The classification of the foliation type and intensity used in this study is based on the characterization procedure introduced by Milnes et al. (2006). The foliation type was estimated macroscopically and classified into five categories: MAS = massive GNE = gneissic

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BAN = banded SCH = schistose IRR = irregular The gneissic type (GNE) corresponds to a rock dominated by quartz and feldspars, with micas and amphiboles occurring only as minor constituents. The banded foliation type (BAN) consists of intercalated gneissic and schistose layers, which are either separated or discontinuous layers of micas or amphiboles. The schistose type (SCH) is dominated by micas or amphiboles, which have a strong orientation. Massive (MAS) corresponds to massive rock with no visible orientations and irregular (IRR) to folded or chaotic rock. The intensity of the foliation is based on visual estimation and classified into the following four categories: 0 = massive or irregular 1 = weakly foliated 2 = moderately foliated 3 = strongly foliated The type and intensity of the foliation was defined for every full metre. Measurements of foliation (Appendix 6) were carried out in one metre intervals from the core sample, if possible. Only alpha-angles was measured, as the sample was not oriented. The direction of the foliation could not be measured in vertical drillholes. The main type of foliation in the core samples OL-PP72...89 is irregular to weakly banded foliation occurring in the diatexitic gneiss. The veined gneiss sections show weakly to moderately banded foliation. The pegmatitic granite is massive and mica gneiss weakly gneissic by foliation. From the core samples OL-PP72...89 a total of 64 measurements were made. The alpha angle varied between 30 and 70 degrees, which gives 60 - 20 degrees dip angle on vertical drillholes. 3.5

Fracturing

Fractures were numbered sequentially from the beginning to the end of the drillcore (Appendix 7). Fracture depths were measured to the centre line of the core and given with an accuracy of 0.01 m. Each fracture was described individually with attributes including orientation, type, colour, fracture filling, surface shape and roughness. The abbreviations used to describe the fracture type are in accordance with the classification used by Suomen Malmi Oy (Niinimäki 2004) (Table 2). Fractures with a filling were classified as filled, if the core was intact. The filled fractures with intact surfaces were described as closed or partly closed. In these cases, “closed” or “partly closed” has been written in the remarks column. The thickness of the filling was estimated with an accuracy of 0.1 mm. The identification of fracture fillings was qualitative and made visually in accordance with the fracture mineral database developed by Kivitieto Oy and Posiva Oy (Table 3). Abbreviations were used during the logging. Where the recognition of a mineral was not possible, the mineral was described with a common mineral group name, such as clay, sulphide etc.

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In addition to this, the morphology and alteration of fractures were also classified according to the Q-system (Grimstad & Barton 1993). The fracture morphology was described with the joint roughness number, Jr (Table 4) and the alteration with the joint alteration number, Ja (Table 5). The fracture shape and roughness of fracture surfaces were classified using a modification of Barton’s Q-classification (Barton et al. 1974) (Table 6). Table 2. The abbreviations used to describe fracture type (Niinimäki 2004). Abbreviation

Fracture type

op

Open

ti

Tight, no filling material

fi

Filled

fisl

Filled slickensided

grfi

Grain filled

clfi

Clay filled

Table 3. Fracture filling mineral abbreviations. Abbreviation CC SV KL BT

Mineral

Abbreviation

Mineral

SK KA IL FH

= Pyrite = Kaolinite = Illite = Fe-hydroxide (rust)

= Calcite = Clay mineral = Chlorite = Biotite

Table 4. Concise description of joint roughness number Jr (Grimstad & Barton 1993). Jr

Profile

Rock wall contact, or rock wall contact before 10 cm shear.

4

SRO

Discontinuous joint or rough and stepped

3

SSM

Stepped smooth

2

SSL

Stepped slickensided

3

URO

Rough and undulating

2

USM

Smooth and undulating

1.5

USL

Slickensided and undulating

1.5

PRO

Rough or irregular, planar

1

PSM

Smooth, planar

0.5

PSL

Slickensided, planar

Note 1. Descriptions refer to small-scale features and intermediate scale features, in that order. Jr

No rock-wall contact when sheared

1

Zone containing clay minerals thick enough to prevent rock-wall contact

1

Sandy, gravely or crushed zone thick enough to prevent rock-wall contact

Note 1. Add 1 if the mean spacing of the relevant joint set is greater than 3. 2. Jr = 0.5 can be used for planar slickensided joints having lineation, provided the lineations are oriented for minimum strength.

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Table 5. Concise description of joint alteration number Ja (Grimstad & Barton 1993). Ja 0.75

Rock wall contact (no mineral filling, only coatings). Tightly healed, hard, non-softening impermeable filling, i.e. quartz, or epidote.

1

Unaltered joint walls, surface staining only.

2

Slightly altered joint walls. Non-softening mineral coatings, sandy particles, clayfree disintegrated rock, etc.

3

Silty or sandy clay coatings, small clay fraction (non-softening).

4

Softening or low-friction clay mineral coatings, i.e. kaolinite, mica, chlorite, talc, gypsum, and graphite, etc., and small quantities of swelling clays (discontinuous coatings, 1-2 mm or less in thickness. Rock wall contact before 10 cm shear (thin mineral fillings).

4

Sandy particles, clay-free disintegrated rock, etc.

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Strongly over-consolidated, non-softening clay mineral fillings (continuous,