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

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1 Working Report Core Drilling of Shallow Drillholes OL-PP72...OL-PP89 at Olkiluoto, Eurajoki 2011 Vesa Toropainen May 2012 POSIVA OY FI OLKILUOTO, FINLAND Tel Fax

2 Working Report 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.

3 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 Soil quality, bedrock depth and quality of near surface bedrock were investigated in this project. The drillholes were drilled between 19 th of October and 8 th of November 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 (OL- PP77) 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.

4 MATALIEN KAIRAREIKIEN OL-PP KAIRAUS OLKILUODOSSA, EURAJOELLA VUONNA 2011 TIIVISTELMÄ Suomen Malmi Oy (Smoy) kairasi kahdeksantoista matalaa kairareikää kapselointilaitoksen pohjatutkimuksia varten Eurajoen Olkiluodossa vuonna 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.

5 1 TABLE OF CONTENTS ABSTRACT TIIVISTELMÄ INTRODUCTION Background Scope of the work... 3 DRILLING OF SHALLOW DRILLHOLES OL-PP72...OL-PP Schedule of the drilling work Description of the drilling work Drilling water and the use of label agent Locations of the drillholes Soil quality observations... 6 GEOLOGICAL LOGGING General Core orientation Lithology Foliation Fracturing Fracture frequency and RQD Fractured zones and core loss Weathering Core discing ROCK MECHANICS The rock quality SUMMARY REFERENCES APPENDICES 1 Technical details of the drillholes Soil quality observations Core boxes Core lifts Lithology Foliation Fractures Fracture frequency and RQD Fractured zones and core loss Weathering Q'-classification CORE PHOTOGRAPHS... 85

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7 3 1 INTRODUCTION 1.1 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 The Finnish Parliament ratified the decision in May 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 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 and ) 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 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.

8 4 Figure 1. The locations of the shallow drillholes OL-PP in ONKALO area, Olkiluoto. Black outline and circle represent the encapsulation plant and shaft.

9 5 2 DRILLING OF SHALLOW DRILLHOLES OL-PP72...OL-PP Schedule of the drilling work The drilling of the shallow drillholes took place in autumn The drilling started at the first drillhole OL-PP79 on the 19 th of October 2011 and the last drillhole OL-PP76 was finished on the 8 th of November 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 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 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.

10 6 Table 1. Surveyed coordinates, lengths and levels of the shallow drillholes. Drillhole X Y Z Z bedrock surface Drillhole length, m Z Drillhole end OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP OL-PP 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.

11 7 3 GEOLOGICAL LOGGING 3.1 General The handling of the core was based on the POSIVA work instructions POS 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

12 8 include homogeneous mica-bearing quartz gneisses, banded mica gneisses and hornblende or pyroxene-bearing mafic gneisses. The migmatitic gneisses, which typically contain % 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-PP consist of diatexitic gneiss (85.73 m, 77.0 %). It is mainly weakly banded or irregular by foliation and contains usually % 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

13 9 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-PP 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-PP a total of 64 measurements were made. The alpha angle varied between 30 and 70 degrees, which gives 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.

14 10 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, J r (Table 4) and the alteration with the joint alteration number, J a (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 Mineral Abbreviation Mineral CC = Calcite SK = Pyrite SV = Clay mineral KA = Kaolinite KL = Chlorite IL = Illite BT = Biotite FH = Fe-hydroxide (rust) Table 4. Concise description of joint roughness number J r (Grimstad & Barton 1993). J r 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. J r 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 Jr = 0.5 can be used for planar slickensided joints having lineation, provided the lineations are oriented for minimum strength.

15 11 Table 5. Concise description of joint alteration number J a (Grimstad & Barton 1993). J a 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. Slightly altered joint walls. Non-softening mineral coatings, sandy particles, clayfree disintegrated rock, etc. 2 3 Silty or sandy clay coatings, small clay fraction (non-softening). Softening or low-friction clay mineral coatings, i.e. kaolinite, mica, chlorite, talc, 4 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. Strongly over-consolidated, non-softening clay mineral fillings (continuous, <5 mm 6 in thickness). Medium or low over-consolidation, softening, clay mineral filling (continuous <5 mm 8 in thickness). Swelling-clay fillings, i.e. montmorillonite (continuous, <5 mm in thickness). Value of 8-12 J a depends on percentage of swelling clay-sized particles, and access to water, etc. No rock-wall contact when sheared (thick mineral fillings) Zones or bands of disintegrated or crushed rock and clay. 5 Zones or bands of silty- or sandy-clay, small clay fraction (non-softening) Thick, continuous zones or bands of clay. Table 6. Fracture surface shapes and roughness (Barton et al. 1974). Fracture shape Fracture roughness Planar Rough Stepped Smooth Undulated Slickensided During the fracture logging, the surface colour was also registered. The colour is often caused by the dominating fracture filling mineral or minerals, e.g. chlorite (green) or kaolinite (white). Presence of minor filling minerals usually causes some variation in the colour of the fracture surface. These colour shades were described e.g. as dark or greenish. Tight fractures typically had only a slightly different shade from the host rock colour. OL-PP In the fracture logging, 547 separate fractures were recorded from drillcores OL-PP (Appendix 7). There are 377 filled fractures, 78 open fractures, 74 tight fractures, 13 grain filled fractures, four clay filled fractures and one filled slickensided fracture (Figure 2). Most of the fractures are with undulated or stepped surfaces with high to moderate joint roughness and low joint alteration numbers (Figures 3, 4 and 5), which indicate high to moderate friction fractures.

16 12 Most of the open fractures are concentrated in the uppermost one - two metres of the drillcore. They have rusty and flushed appearance, but also can contain small amounts filling minerals. Filled fractures are common throughout the drillcore. The fracture fillings are generally thin, rarely exceeding 1 mm. Some fractures and breaks, especially at the ends of the lifts contain grey clay-like material, but the filling is most probably fine grained drill cuttings. The process of the drill cuttings concentrating on the last fractures of the lift is not known. It's possible that some of these drill cuttings are logged as SV fillings, when occurring in natural fractures among other filling minerals. The identified fracture filling minerals of OL-PP according to the frequency of occurrence are: kaolinite, unidentified clay minerals, calcite, ferrous hydroxides (rust), chlorite, illite, graphite and muscovite. Figure 2. Fracture types of the logged fractures in the drillcores OL-PP For explanations, see table 2. Figure 3. Fracture morphologies of the logged fractures in the drillcores OL-PP For explanations, see tables 4 and 6.

17 13 Figure 4. Joint roughness numbers of the logged fractures in the drillcores OL-PP For explanations, see Table 4. Figure 5. Joint alteration numbers of the logged fractures in the drillcores OL-PP For explanations, see Table Fracture frequency and RQD The frequencies of natural fractures, RQD (Rock Quality Designator) (see Table 9) and mechanically induced breaks were all counted on one metre depth intervals (Appendix 8). The frequency of all fractures is the number of core breaks within one metre interval, including natural fractures and mechanically induced breaks. Mechanically induced breaks are caused by drilling, core handling and core discing. The natural fracture frequency is the number of natural fractures, open and closed, within one metre interval. If the frequency of all fractures is higher than the natural fracture frequency, the core must have been broken during the drilling. If the core was broken accidentally or by purpose during handling, it was marked to the core box with the letter F, and counted as a fracture

18 14 or break depending on its nature. If the natural fracture frequency is higher than the frequency of all fractures, the fractures must be cohesive enough to keep the core together. The RQD gives the percentage of over 10 cm long core segments, separated by natural fractures, within one metre interval. The average natural fracture frequencies of the drillcores range from 2.5 pc/m (OL-PP77) to 11.8 pc/m (OL-PP86). However in most of the drillcores it is between 3 and 6 pc/m. The average RQD ranges from 55.1 % (OL-PP86) to 96.4 % (OL-PP77), respectively. The average RQD in the drillcores mainly varies from 80 to 95 %. The average fracture frequency and RQD of the drillcore OL-PP79 are 6.8 pc/m and 79.8 % (Appendix 8). The strongest fracture frequencies are concentrated in the drillholes located in the west centre parts of the study area (OL-PP78, 79, 80, 81, 84 and 86). 3.7 Fractured zones and core loss Fractured zones were classified according to Finnish engineering geological bedrock classification (Korhonen et al. 1974) (Table 7). In the drillholes, there are 13 sections classified as fractured zones (Appendix 9). The fractured zones occupy 15.2 meters of the total length of the drillcores (13.7 %). All of the fractured zones are fracture structured (RiIII) by their type, even though there were some thin grain and clay fillings in some of the fractures. Some of the drillholes (OL-PP75, 76, 77, 79, 81 and 83) showed a short fractured zone in the uppermost section of the sample, which commonly included rusty open fractures. These drillholes are located in the east side of the investigation area. The deeper lying fractured zones contained tight and filled fractures, but with quite thin fillings. The deeper lying fractured zones are concentrated into the four drillholes near each other (OL-PP78, 79, 80 and 86). In the drillcore OL-PP79 there are four fractured zones. The uppermost of them ( m) contain mainly open fractures, whereas the three lower lying zones are composed of very thinly filled, or tight, fractures. Table 7. Classification of fractured rock (Korhonen et al. 1974). Broken rock mass Zone class Fractures / m Fracture filling Block structured RiII 3-10 no fillings Fracture structured RiIII > 10 none or thin Crush structured RiIV-Rk3 / RiIV-Rk / > 10 filled with clay minerals Clay structured RiV - abundant clay material in rock mass In the drillcores OL-PP72, 73, 74, 82, 84, 85, 87 and 88 no fractured zones were intersected. They are located in the north-west side and southernmost corner of the study area. Significant core loss due to non-cohesive rock was not observed. Core loss due to rock breaking or grinding is mainly insignificant in the drillholes, and occurs mainly in the first 0.5 m where the casing drilling has partly broken the sample (Appendix 9).

19 Weathering The weathering degree of the drillcore was classified according to the method developed by Korhonen et al. (1974) and Gardemeister et al. (1976) (Table 8). The drillcores OL-PP consist mainly (total of m, 83.2 %) of rock that shows surface alteration and slight weathering, classified as Rp1. The alteration is mainly spotty and stripy kaolinitization accompanied with weak illitization, sulphidization and graphite on foliation planes. Some parts of the samples (total of m, 16.2 %) are unweathered (Rp0), showing only very weak and mostly local alteration (surface oxidation of feldspars, sulphidization with graphite), or no visible alteration at all. In the drillcore OL-PP81 there are also two short sections ( m, m) of strongly weathered rock with strong illitization and chloritization, making the rock soft and fragile. The drillcore OL-PP79 is classified as slightly weathered (Rp1) (Appendix 10). Table 8. Abbreviations of the weathering degree. Abbreviation Rp0 Rp1 Rp2 Rp3 Description of weathering type Unweathered Slightly weathered Strongly weathered Completely weathered 3.9 Core discing In Posiva s logging procedure, core discing is logged separately, and depth intervals where core discing occurs are documented. The number of breaks and core discs is logged. The geometry of the top and bottom surfaces of the discs is described separately using the following classification: - Concave - Convex - Planar - Saddle - Incomplete. No core discing was found in the drillcores.

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21 17 4 ROCK MECHANICS 4.1 The rock quality Rock quality was classified during the core logging using Barton s Q-classification (Rock Tunneling Quality Index; Barton et al and Grimstad & Barton 1993). The core is divided into sections, which can vary from less than a metre to several metres in length. In each section, the rock quality is as homogenous as possible. The roughness and alteration numbers are estimated for each fracture surface (Appendix 7). The roughness and alteration numbers (average, median and lower and higher quartiles) are then calculated for each section, and the median value is used in the rock quality calculations. The Q-value is calculated by Equation 1 (Barton et al and Grimstad & Barton 1993): Q RQD J * J J n r a J w * SRF (1) The RQD (Table 9) is defined as the cumulative length of core pieces longer than 10 cm in a run divided by the total length of the core run. Closed fractures are also counted in the RQD value. Some constant values are used in the calculations. All closed fractures are given joint alteration (J a ) number of 0.75 (see Table 5). If the fracture interval of the relevant joint set is over one metre, the value of 1 is given to J n (Table 9). If the fracture interval of the relevant joint set is over three metres, the value of 1 is added to the value of J r, (see Table 4), and J n is given the value of 0.5. For rock sections with no fractures, the value of 5 for J r and the value of 0.75 for J a are used. In the calculations, joint water (J w ) and stress reduction factors (SRF) are assumed as 1, so the result of the calculation is the Q -value. The core samples of OL-PP were divided to 41 units of variable lengths, the Q - values of which were then calculated separately. Some drillholes, especially short ones, are only handled as one section, whereas some longer drillholes were divided into maximum of seven separate sections (OL-PP79). The fractured zones were always considered as their own sections. The results of Q -classification are presented in Appendix 11. The rock quality of drillcores OL-PP is mainly good (72.73 m, 65.0 %) or very good (30.50 m, 27.0 %). In addition some short sections of "exceptionally good" (3.32 m, 3,0 %) and "extremely good" (0.60 m, 0.5 %) were encountered. The fractured zones are mainly classified as "good" or "fair" (4.13 m, 3.7 %). The drillcore OL-PP79 is classified mainly as "good".

22 Table 9. Description of RQD and joint set number J n (Grimstad & Barton 1993). 18

23 19 5 SUMMARY In connection with constructing the encapsulation plant for ONKALO facility, Posiva Oy ordered Suomen Malmi Oy to drill 18 shallow drillholes (OL-PP ) to investigate the thickness and quality of overburden and the quality of near surface bedrock. The shallow drillholes were drilled with a GM-75 drill rig. The drillholes were started by drilling a stainless steel casing to the bedrock and continuing the drillhole with T76 core drilling equipment to the final drilling depth. The drillholes were let to fill with ground material after drilling, no casings were left at place. The drilling water was marked with sodium fluorescein. The core samples were logged following Posiva's standard procedure. The main rock type intersected by the drillholes is diatexitic gneiss. Also veined gneiss, pegmatitic granite and mica gneiss was observed. The rock samples are mostly slightly surface weathered. The average natural fracture frequencies of the drillcores range from 2.5 pc/m (OL-PP77) to 11.8 pc/m (OL-PP86). The average RQD ranges from 55.1 % (OL-PP86) to 96.4 % (OL-PP77), respectively. In the drillcores thirteen fractured zones were intersected.

24 20

25 21 REFERENCES Barton, N., Lien, R. & Lunde, J Engineering classification of rock masses for the design of tunnel support. Rock Mechanics. December Vol. 6 No. 4. SpringerVerlag. Wien, New York pp. Gardemeister, R., Johansson, S., Korhonen, P., Patrikainen, P., Tuisku, T. & Vähäsarja, P Rakennusgeologisen kallioluokituksen soveltaminen. (The application of Finnish engineering geological bedrock classification, in Finnish). Espoo: Technical Recearch Centre of Finland, Geotechnical laboratory. 38 p. Research note 25. Grimstad, E. & Barton, N Updating of the Q-system for NMT. Proceedings ofsprayed Concrete, December Fagernäs, Norway Korhonen, K-H., Gardemeister, R., Jääskeläinen, H., Niini, H. & Vähäsarja, P Rakennusalan kallioluokitus. (Engineering geological bedrock classification, in Finnish). Espoo: Technical Research Centre of Finland, Geotechnical laboratory. 78 p. Research note 12. Kärki, A. & Paulamäki, S Petrology of Olkiluoto. POSIVA Posiva Oy, Eurajoki. Mattila, J A System of Nomenclature for Rocks in Olkiluoto. Eurajoki, Finland: Posiva Oy. Posiva Working report Milnes, A. G., Hudson, J., Wikström, L. & Aaltonen, I Foliation: Geological Background, Rock Mechanics Significance, and Preliminary Investigations at Olkiluoto. Working Report Posiva Oy, Eurajoki. Niinimäki, R Core drilling of Pilot Hole OL-PH1 at Olkiluoto in Eurajoki Eurajoki, Finland: Posiva Oy. Posiva Working report , 95 p.

26 22

27 HOLE_ID OLPP72 OLPP73 OLPP74 OLPP75 OLPP76 OLPP linear linear linear linear linear linear Olkiluoto Olkiluoto Olkiluoto Olkiluoto Olkiluoto Olkiluoto Prismarit Prismarit Prismarit Prismarit Prismarit Prismarit Plannedlocation Plannedlocation Plannedlocation Plannedlocation Realizedlocation Realizedlocation KKJ1 KKJ1 KKJ1 KKJ1 KKJ1 KKJ nocasing nocasing nocasing nocasing nocasing nocasing T76 T76 T76 T76 T76 T , , , , , ,978911

28 HOLE_ID OLPP78 OLPP79 OLPP80 OLPP81 OLPP82 OLPP linear linear linear linear linear linear Olkiluoto Olkiluoto Olkiluoto Olkiluoto Olkiluoto Olkiluoto Prismarit Prismarit Prismarit Prismarit Prismarit Prismarit Plannedlocation Plannedlocation Plannedlocation Plannedlocation Plannedlocation Plannedlocation KKJ1 KKJ1 KKJ1 KKJ1 KKJ1 KKJ nocasing nocasing nocasing nocasing nocasing nocasing T76 T76 T76 T76 T76 T , , , , , ,978911

29 HOLE_ID OLPP84 OLPP85 OLPP86 OLPP87 OLPP88 OLPP linear linear linear linear linear linear Olkiluoto Olkiluoto Olkiluoto Olkiluoto Olkiluoto Olkiluoto Prismarit Prismarit Prismarit Prismarit Prismarit Prismarit Plannedlocation Realizedlocation Plannedlocation Plannedlocation Plannedlocation Plannedlocation KKJ1 KKJ1 KKJ1 KKJ1 KKJ1 KKJ nocasing nocasing nocasing nocasing nocasing nocasing T76 T76 T76 T76 T76 T , , , , , ,978911

30

31 OLPP72 M_from M_TO Observation Remarks m m fill silt till bedrock OLPP73 M_from M_TO Observation Remarks m m fill till bedrock OLPP74 M_from M_TO Observation Remarks m m fill bedrock OLPP75 M_from M_TO Observation Remarks m m fill 0.70 bedrock OLPP76 M_from M_TO Observation Remarks m m fill 0.40 bedrock OLPP77 M_from M_TO Observation Remarks m m fill 0.90 bedrock OLPP78 M_from M_TO Observation Remarks m m fill gravel 2.80 bedrock

32 OLPP79 M_from M_TO Observation Remarks m m fill 0.60 bedrock OLPP80 M_from M_TO Observation Remarks m m fill (rocks?) 2.05 bedrock OLPP81 M_from M_TO Observation Remarks m m fill (gravel?) 1.15 bedrock OLPP82 M_from M_TO Observation Remarks m m fill (gravel?) 0.50 bedrock OLPP83 M_from M_TO Observation Remarks m m fill (gravel?) 0.80 bedrock OLPP84 M_from M_TO Observation Remarks m m gravel (fill?) clay,sand 4.40 bedrock OLPP85 M_from M_TO Observation Remarks m m fill gravel 2.70 bedrock

33 OLPP86 M_from M_TO Observation Remarks m m fill (rocks?) gravel 2.15 bedrock OLPP87 M_from M_TO Observation Remarks m m fill (rocks) gravel,clay 4.45 bedrock OLPP88 M_from M_TO Observation Remarks m m fill clay,sand 2.22 bedrock OLPP89 M_from M_TO Observation Remarks m m gravel,rocks (fill?) till 2.88 bedrock

34

35 OLPP72 OLPP73 OLPP74 OLPP75 OLPP76 OLPP77 OLPP78

36 OLPP79 OLPP80 OLPP81 OLPP82 OLPP83 OLPP84 OLPP85

37 OLPP86 OLPP87 OLPP88 OLPP89

38

39 OLPP72 OLPP73 OLPP74 OLPP75 OLPP76

40 OLPP77 OLPP OLPP OLPP80 OLPP81

41 OLPP82 OLPP83 OLPP84 OLPP85 OLPP OLPP87

42 OLPP88 OLPP89

43 OLPP72 OLPP73 OLPP74 OLPP75 OLPP76

44 OLPP77 OLPP78 OLPP79 OLPP80

45 OLPP81 OLPP82 OLPP83 OLPP84 OLPP85

46 OLPP86 OLPP87 OLPP88 OLPP89

47 OLPP72 OLPP73 OLPP74 OLPP75

48 OLPP76 OLPP77 OLPP78

49 OLPP79 OLPP80 OLPP81

50 OLPP82 OLPP83 OLPP84 OLPP85

51 OLPP86 OLPP87 OLPP88 OLPP89

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73 OLPP72 OLPP73 OLPP74 OLPP75 OLPP76

74 OLPP77 OLPP78 OLPP79 OLPP80 OLPP81

75 OLPP82 OLPP83 OLPP84 OLPP85 OLPP86 OLPP87

76 OLPP88 OLPP89

77 OLPP72 OLPP73 OLPP74 OLPP75 OLPP76 OLPP77 OLPP78

78 OLPP79 OLPP80 OLPP81 OLPP82 OLPP83 OLPP84 OLPP85 OLPP86

79 OLPP87 OLPP88 OLPP89

80

81 OLPP72 OLPP73 OLPP74 OLPP75 OLPP76 OLPP77

82 OLPP78 OLPP79 OLPP80 OLPP81 OLPP82 OLPP83

83 OLPP84 OLPP85 OLPP86 OLPP87 OLPP88 OLPP89

84

85 OLPP72 OLPP73 OLPP74 OLPP75 OLPP76 OLPP77

86 OLPP78 OLPP79 OLPP80 OLPP81 OLPP82 OLPP83

87 OLPP84 OLPP85 OLPP86 OLPP87 OLPP88 OLPP89

88

89 OL-PP72 OL-PP73

90 OL-PP74

91 OL-PP75

92 OL-PP76

93 OL-PP77

94 OL-PP78

95 OL-PP79

96 OL-PP80 OL-PP81

97 OL-PP82

98 OL-PP83

99 OL-PP84 OL-PP85

100 OL-PP86 OL-PP87

101 OL-PP88 OL-PP89

102 98