Investigation of rock porosity and microfracturing with 14 C-PMMA method

Transcription

1 Working report 97-54e Investigation of rock porosity and microfracturing with 14 C-PMMA method The blast samples from the walls of the Research Tunnel at Olkiluoto Marja Siitari-Kauppi University of Helsinki Laboratory of Radiochemistry Jorma Autio Saanio & Riekkola Oy December 1997 POSIVA OY Mikonkatu 15 A, FIN HELSINKI, FINLAND Tel Fax

2 Working report 97-54e Investigation of rock porosity and microfracturing with 14 C-PMMA method The blast samples from the walls of the Research Tunnel at Olkiluoto Marja Siitari-Kauppi University of Helsinki Laboratory of Radiochemistry Jorma Autio Saanio & Riekkola Oy December 1997

3 UNIVERSITY OF HELSINKI LABORATORY OF RADIOCHEMISTRY Comissioned by: Posiva Oy Mikonk:atu 15 A FIN , Helsinki, Finland Order: 9594/96/JPS Posiva Contact persons: Jukka-Pekka Salo, Posiva~ Marja Siitari-Kauppi, HYRL Jorma Autio, Saanio&Riekkola INVESTIGATION OF ROCK POROSITY AND MICROFRACTURING WITH 14 C-PMMA METHOD The blast samples from the walls of the Research Tunnel at Olkiluoto Authors: /;/;A; 0 L 1/.., ' r(bw j1 t!lj 't./#j :- FK Marja Siitari-Kauppi Research scientist TkL Jorma Autio Project manager Approved by: Timo Jaa Professor

4 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.

5 INVESTIGATION OF ROCK POROSITY AND MICROFRACTURING WITH 14 C-PMMA METHOD - The blast samples from the walls of the Research Tunnel at Olkiluoto SUMMARY The porosity and microfracturing of the blast samples from the walls of the Research Tunnel at Olkiluoto in Eurajoki were investigated with the 14 C-PMMA method. The method involved impregnation of the rocks with 14 C methylmethacrylate, irradiation polymerization, autoradiography and optical densitometry with digital image processing techniques. Scanning electron microscopy (SEM) and energy dispersive X ray analysis (EDS) were used to investigate in greater detail the pore apertures and minerals in porous regions. SEM!EDS measurements were conducted on 14 C-MMAimpregnated samples. The disturbance adjacent to the blastholes caused by blasting at different charge densities was studied. The porosities of the undisturbed rock matrix ranged from 0.05 to 0.2%. The appearance of fractures varied between different blast samples from a few detections to a great number of them. Some of them extended to the depths of centimetres from the blasthole surface. The fractures could be visualized with naked eye from the sawn rock surface, too. From the porosity profiles measured, excluding the long and wide fractures, it was observed a clear increase in porosity to a depth of mm from the blasthole surface. The porosities in the disturbed zone varied between vol.%. SEMIEDS measurement was conducted on blast sample 1. Several intra- and transgranular fissures were observed in all mineral grains at depths of 0 to 5 mm from the disturbed surface. The apertures ranged from a few to several micrometers. Fissures, which were observed with naked eye, had apertures from tens to hundreds of micrometers according to SEM analysis. Keywords: porosity, microfracturing, 14 C-PMMA method, autoradiography, digital image analysis, SEMIEDS, excavation disturbance

6 KIVEN HUOKOISUUDEN JA MIKRORAKOILUN TUTKIMUS 14 C-PMMA MENETELMALLA - Olkiluodon tutkimustunnelin seinista kairatut rajaytyshairionaytteet TllVISTELMA Esitetyssa tyossa, joka on osa laajempaa rajaytyksen aiheuttaman hairiovyohykkeen tutkimusta, tutkittiin rajaytyksen aiheuttamaa hairiota. Hairion syvyysulottuvuutta, rakennetta, rakoiluaja huokoisuutta tutkittiin laboratoriossa 14 C-PMMA menetelmalla ja elektronimikroskooppisesti. Tutkitut naytteet oli kairattu Eurajoen Olkiluodossa sijaitsevan tutkimustunnelin seinista ja ne edustivat eri rajaytysaineen panostusasteita. Hairion sisaltavat naytteet impregnoitiin 14 C leimatulla metyylimetakrylaatilla (MMA) vakuumikuivauksen jalkeen. Monomeeri polymeroitiin Co-60 sateilylahteen kentassa. Impregnoidut kivet sahattiin ja sahatut pinnat tutkittiin autoradiografisesti. Huokoisuusprofiilit ja huokoisuuden jakaumat maaritettiin autoradiogrammeista digitaalisen kuvienkasittelyn avulla. Huokosrakenteiden ja niita ymparoivien mineraalien elektronimikroskooppiset tarkastelut tehtiin 14 C-PMMA kasitellyille kivinaytteille. Hairiottoman vyohykkeen keskimaarainen huokoisuus oli vol.% mitattuna noin 40 mm:n syvyydelle hairiopinnasta. Rajaytyksen aiheuttama hairio ilmeni rakoiluna rajaytyspinnasta kohti hairiotonta kivimatriisia. Raot ulottuivat useiden millimetrien syvyyteen pisimpien halkaistessa koko tutkittavan kivisylinterin (noin 30 cm). Rakoilun maara vaihteli naytteiden valilla ollen vahaisinta naytteissa 7 ja 8, voimakasta naytteissa 4 ja 13 seka erittain voimakasta naytteissa 1, 2 ja 14. Huokoisuusprofiilit mitattiin siten, etta niihin ei sisaltynyt syvalle ulottuvaa rakoilua. Huokoisuuden kasvun rajaytysreian seinamasta hairiottomaan kiveen havaittiin ulottuvan noin mm syvyyteen. Hairiovyohykkeen keskimaaraiset huokoisuudet vaihtelivat valilla vol.%. Naytteen 1 elektronimikroskopiatarkastelussa havaittiin mineraalikiteiden valista ja sisaista mikrorakoilua. Naiden rakojen avaumat olivat muutamia mikrometreja. Useita mineraalikiteita halkova senttimetrien pituinen rako havaittiin kiven pinnasta myos silmamaaraisesti ja taman raon avauma vaihteli 50 mikrometrista 200 mik:rometriin. Avainsanat: huokoisuus, mikrorakoilu, 14 C-PMMA menetelma, autoradiografia, digitaalinen kuvienkasittely, SEMIEDS, louhinnan aiheuttama hairio

7 TABLE OF CONTENTS PREFACE TIIVISTELMA SUMMARY 1 INTRODUCTION 2 SAMPLES 2.1 General 2.2 Partitioning of samples before and after impregnation INVESTIGATION OF SAMPLES WITH 14 C-PMMA METHOD 3.1 Properties of 14 C-MMA tracer Drying, impregnation with 14 C-MMA tracer Autoradiography Digital image analysis of autoradiographs Calculation of porosity The intensity and the optical density The activity and optical density The porosity 9 4 ELECTRON MICROSCOPIC MEASUREMENTS 11 5 RESULTS OF 14 C-PMMA ANALYSIS Sample Sample Sample Sample Sample Sample Sample 14 21

8 6 RESULTS OF SCANNING ELECTRON MICROSCOPY 6.1 Structure of sample CONCLUSIONS AND DISCUSSION 29 REFERENCES APPENDICES

9 PREFACE The work was carried out by Marja Siitari-Kauppi in co-operation with Jorma Autio at the Laboratory of Radiochemistry, Department of Chemistry, of the University of Helsinki. This study is part of the characterisation of the disturbance caused by blasting in the walls of the Research Tunnel at Olkiluoto, which is being carried out by Posiva Oy. The work was commissioned by Jorma Autio of Saanio&Riekkola Oy, on behalf of Posiva Oy and the contact person at Posiva was Jukka-Pekka Salo. Timo Kirkkomaki of Saanio&Riekkola Oy made the partition diagrams of the samples presented in the Appendices. Electron microscopy measurements were performed at the Department of Electron Microscopy, University of Helsinki.

10 1 INTRODUCTION The full-scale deposition holes were bored in the beginning of 1994 at Olkiluoto. Extensive geoscientific characterisation preceded the boring, and was followed by an extensive characterisation programme /1-4/ that included studies focusing on the disturbance caused by excavation. In 1995 this disturbance was studied in the laboratory, using 98 mm diameter core samples taken from different locations in the holes /5/. A novel 14 C-polymethylmethacrylate ( 14 C-PMMA) method /6-9/ and scanning electron microscopy were applied to evaluate the extent and nature of the disturbance. In addition, a novel Helium gas diffusion method was employed to determine the diffusion coefficient and permeability of both disturbed and undisturbed rock /10/. EXPERIMENTAL DEPOSITION HOLES Figure 1. VLJ Repository and Research Tunnel at Olkiluoto. The 16 samples including the half-barrels of blastholes were taken from the walls of the Research Tunnel at Olkiluoto in Eurajoki, in1996 (Fig.1 ). The samples are used to study the blast disturbance adjacent to the blastholes caused by blasting at different charge densities. /11,12/ Seven of those samples were chosen to be studied using the 14 C PMMA method. 1

11 The 14 C-PMMA method makes it possible to study the spatial distribution of the pore space and the heterogeneities of rock matrices on submicrometric to centimetric scales. Subsequent autoradiography and digital image analysis enable features limited in size by the range of 14 C beta radiation to be measured. The porous zones detected with the 14 C-PMMA method were studied qualitatively in more detail by using scanning electron m1croscopy. The general objective of the work described in this report was to determine the disturbance adjacent to the blastholes caused by blasting. Aspects studied included the determination of porosity, analysis of micro fracturing and investigation of the structure of the zone. The results of the 14 C-PMMA study, which are presented in this report, are part of a larger research entity which includes other studies focusing on the disturbance caused by blasting. 2 SAMPLES 2.1 General The seven rock samples from different parts of the Research Tunnel, and representing blasting at different charge densities, were taken from the walls of the tunnel (Figure 1 ). Most of the samples were taken from the stem section of the original blasthole. The locations of the sampling sections, and the corresponding parameters, are presented in Reference 2 and 12. The cylindrical rock samples were 98 mm in diameter and about 300 mm in length. The seven blast samples, named as group 9, collected from the tunnel walls were impregnated together with the samples cored from the full-scale experimental deposition holes, the results of which are presented elsewhere /13/. 2

12 The group 9 comprised samples 1, 2, 4, 7, 8, 13 and 14 of gneissic tonalite. Samples for electron microscopic study were prepared from blast sample 1.11/B following the 14 C PMMA treatment. 2.2 Partitioning of the samples before and after impregnation A schematic presentation of the sawing procedures used for each individual sample is shown in Appendices 1 to 7. The procedure for sample 1 is presented in Figure 2 as an example. INSI NOORITO IMISTO.,n SAANIO & RIEKKOLA oy...1 ED /\ 1.ll/ A 1.ll/8 I SEM 1.ll/ ll/ A la l. ~ U 8 9 mm l.ll/8 11 SEM Figure 2. Partition diagram of sample 1 from the Research Tunnel. The dashed line in the diagrams divides the procedure into partition of the samples before and after impregnation. The sawing after impregnation was done for 3

13 autoradiography, scanrung electron m1croscopy (SEM) and mineral composition characterisation with thin slice samples using polarisation microscopy. The shaded sawed surfaces in the partition diagrams were exposed on autoradiographic film, and several autoradiographs were taken of the sawn surfaces. The code of a sawn rock piece is the same as that of the autoradiograph taken from the sawn surface. Each part of the sample is coded according to its proximity to the blasthole surface. For example, the first cut, which was made for a porosity profile, was along the axis of the cylindrical sample and the half barrel of the blasthole can be seen in autoradiograph. The samples were then sawn parallel to the blasthole surface, which contained the disturbed zone at depths of 5 mm to 25 mm from the bottom of the hole. The diamond saw used in the experiment was of the Eurocoup-Masonry type. The thickness ofthe blade was 1.8 mm and the diameter 350 mm. The speed of rotation was 2800 rpm and the loss of rock matrix 2.1 mm. 3 INVESTIGATION OF SAMPLES WITH 14 CPMMA METHOD The 14 C-PMMA method involves impregnation of centimetric scale rock cores with 14 C labelled methylmethacrylate ( 14 C-MMA) in a vacuum, irradiation polymerisation, autoradiography and optical densitometry with digital image processing techniques /6-9/. Impregnation with the labelled low-molecular-weight and low-viscosity monomer 14 C-MMA, which wets the silicate surfaces well and can be fixed by polymerisation, provides information on the accessible pore space in crystalline rock that cannot be obtained with other methods. Total porosity is calculated by using 2D autoradiographs of the sawn rock surfaces. The autoradiographs are converted to corresponding porosity images. The preconditions for applying this method are: (i) known local bulk density; (ii) presence of only two phases mineral and PMMA; and (iii) homogeneous distribution of pores and minerals below 4

14 the limit of lateral resolution of autoradiography. Fissures and cracks with assumed apertures larger than 20 ~-tm were excluded from the quantitative measurements. 3.1 Properties of the 14 C-MMA tracer Methylmethacrylate (MMA) is a monomer with very low viscosity, P (20 C) /14/, while the viscosity of water is P (25 C) 115/. Because its contact angle on silicate surfaces is low, impregnation of bulk rock specimens is rapid and depends on existing pore apertures. The MMA molecule is small. It has non-electrolytic properties and only low polarity, the polarity of the ester being considerably lower than that of water, and it behaves in the rock matrix like a non-sorbing tracer. The low B energy of the carbon-14 isotope, max 150 ke V, is convenient for autoradiographic measurements. The monomer used was 14 C-labelled MMA with a specific activity of 2-5 mci/g and a total activity of 50 mci. Its radiochemical purity was >95 %. In this study the dilution of the tracer ranged between Bq/ml (50 ~-tci/ml) and Bq/ml (25 ~-tci/ml). The tracer activity used was determined after every impregnation with liquid scintillation counting (Rackbeta 280); the dilutions are presented in Table I. The calibration sources were prepared by diluting the 14 C-MMA with inactive MMA. The activities ranged from 462 Bq/ml (12.5 nci/ml) to Bq/ml (5 ~-tci/ml). 3.2 Drying, impregnation with 14 C-MMA and polymerisation of samples Samples were vacuum dried in a chamber for 8 to 14 days at a maximum temperature of 80 C. After drying they were cooled to 18 C. For 14 C-MMA impregnation, the tracer was put into a 50 ml reservoir and transferred under vacuum to the impregnation chamber. Slow transfer of the monomer ensures degassing of the monomer and infiltration of vapour only. The blast samples were impregnated with 14 C-MMA in five stages, using the impregnation times shown in Table 1. The impregnation time ranged 5

15 from 12 to 22 days. After impregnation the samples were irradiated with gamma rays from a Co-60 source, in order to polymerise the monomer in the rock matrix; the required dose was 50 kgy. The samples were irradiated under water 14 C-MMA emulsion in polyethylene vials. 3.3 Autoradiography Irradiation of the rocks with Co-60 causes strong thermoluminescence of K-feldspar and other major rock-forming minerals, which exposes autoradiographic film. To avoid this, the thermoluminescence was released by heating samples to 120 C for 3 hours before sawing. Mylar foil with aluminium coating was placed on top of the film to shield it from the rest of the emissions. The heated samples were sawed into pieces as shown in Appendices 1-7. The sawn rock surfaces were exposed on ~film (Hyperfilm-~max) or more sensitive Kodak BioMax MS autoradiographic film. Both films are high-performance autoradiographic films for 14 C and other low energy ~-emitting nuclides having similar a few ~-tm lateral resolution. The final resolution depends on the roughness of the sawn surface and the range of the 150 ke V beta particles in the rock matrix. As to the range, the rock samples used were infinite in thickness. The beta absorption correction is obtained from the ratio of the densities of rock and polymethylmethacrylate. With the tracer activity and the autoradiographic films employed here, the exposure times for samples ranged from 14 to 32 days. The impregnation and exposure times for each rock sample are listed in Table 1. 6

16 Table 1. Codes of rock samples, the 14 C-MMA tracer activities that were used (1), impregnation times (11) and exposure times of autoradiographs (Ill). sample I (Ci/ml) 11 (d) Ill( d) / / / Digital image analysis of auto radiographs Calculation of porosity Interpretation of the results is based on digital image analysis of autoradiographs. Digital image analysis starts from dividing the autoradiograph into area units called pixels. In this work, dpi resolution was used in the quantitative analysis; this means a pixel size of 85x85 J.lm - 64x64 J.lm. Basically all the intensities of the subdomains were converted into corresponding optical densities, which in turn were converted into activities with the help of the calibration curves measured for each exposure. Finally, the activities were converted into respective porosities. In principle, the interpretation is based on studying the abundance of tracer in each subdomain. 7

17 3.4.2 Intensity and optical density Since the response of the image source (video camera or table scanner) and the amplifier of the digital image analysator are linear, the digitised grey levels of the film can be handled as intensities. Intensity here means the light intensity coming through the autoradiographic film. Optical densities, which according to Lambert & Beer' s law are concentration proportional, are derived from the intensities: (1) where D is the optical density, I 0 is the intensity of the background and I is the intensity of the sample. It can be seen that as the intensity decreases (i.e. the film darkens ), the optical density increases Activity and optical density A conversation function is needed to relate the optical densities (grey levels) measured to corresponding activities. Pure 14 C-PMMA standards having specific activities between 462 and Bq/ml have been used to establish the calibration function. The following calibration curve was used: where Dmax is the maximum optical density, k is a fitting parameter, and A is the specific activity. Solving A from the Eq. (2) gives: (2) A= -k- 1 ln(l- D / Dmax ) (3) 8

18 3.4.4 Porosity The local porosity E of the sample was simply obtained from the abundance of the tracer (assuming constant tracer concentration in the P-MMA, the higher the abundance of the tracer, the higher the local porosity): (4) where A 0 is the specific activity of the tracer used to impregnate the rock matrix, and ~ is the ~-absorption correction factor. The absorption of ~ radiation in a substance depends roughly linearly on the density of the substance. Therefore factor ~ can be approximated from: f3 =PsI Po (5) where Psis the density ofthe sample and p 0 is the density of pure P-MMA (1.18 g/cm 3 ). In the interpretation the sample is assumed to consist of rock materal and pores (containing PMMA), and therefore Ps can be expressed as: (6) where Pr is the density of mineral grains. In the practice of bulk measurements the average density of the rock sample is used. Using Eqs.(5) and (6) in Eq.(4), the porosity and the activity relationship can be solved: (7) where A is the specific activity of individual pixel and Ao is the specific activity of the tracer. The porosity of each individual pixel n from the autoradiogram is calculated according to equations (3) and (7). The porosity histogram gives the relative frequency of regions of individual porosities. The total porosity is obtained from the porosity distribution by taking the weighted average: 9

19 LArean&n --'n-' tol = LArean n (8) where Are~ is the area of pixel n, and En is the local porosity of pixel n. The intensities of autoradiograms are digitised with a CCD camera or a table scanner. The maximum optical resolution of the scanner is 600 dpi, but in this work the resolution for the scanning was usually 300 dpi. The amount of tracer in the sample, and the volumetric porosity, can thus be derived from the blackening of the film caused by the radiation emitted from the plane surface of the rock section. If the pore sizes are well below the resolution of the autoradiography, the major fraction of the beta radiation emitted is attenuated by silicate. The tracer can thus be considered diluted by silicate. For the 14 C-PMMA method to be used, the bulk density must be known; there must be only two phases (mineral and PMMA), and pores and minerals must be homogeneously distributed below the limit of the lateral resolution of the autoradiography. Fissures or cracks with apertures of 20 J-Lm or more are not comparable with calibration sources. The porosity profiles were measured from the autoradiographs taken from the surfaces of sawn rock samples. Each profile contains 3 to 7 measurements where the thickness of digitally scanned sector is 5 to 10 mm. The autoradiograph of sample 7 is shown in Figure 3, and the four porosity profiles that were measured are shown in Figure 4. The total porosity profile of each sample is the arithmetic average of the sectors measured. 10

20 Figure 3. Autoradiograph of rock sample 7.1/A from tunnel wall, showing the sections used to measure the porosity profiles c ~ 0.25 ~ u; 0.2 e 0 c ~sector1 -sector2...,_sector sector sector distance (mm) Figure 4. Porosity profiles measured from autoradiograph of sample 7.1/ A; section I shown in Fig ELECTRON MICROSCOPIC MEASUREMENTS Scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDS) were performed in order both to study the pore apertures of porous regions in greater detail and to identify the corresponding minerals. The regions for SEM/EDS measurements were selected from 14 C-PMMA autoradiographs. 11

21 The sample selected for SEM/EDS determinations was 1.11/B I. The sawing scheme for SEM/EDS sample, and also for thin slice samples, is illustrated in partition diagram in Appendix 1. The mineral analysis for rock samples was performed using thin slices about 60 J..Lm thick and polarisation microscopy. The thin slice and the SEM rock sample will be exposed on autoradiographic film afterwards. Electron microscopic analysis of polished rock sections (polished with 0.25 J..Lm diamond paste) was performed using a Zeiss DSM 962 electron microscope and the Link ISIS program with a UTW Si(Li) detector operated in the backscattered electron image (BSE) mode. The main minerals were determined with energy dispersive X-ray microanalysis (EDS). The samples were carbon coated. Magnifications of up to 2000-fold were used to reveal apertures down to a size of 500 nm. The range of aperture measurements is limited, since according to our experience, SEM examination of the polished surfaces of dense granitic rock samples does not reveal apertures less than 1 J..Lm in diameter, unless the matrix is altered or weathered. The impregnation of the sample with MMA is beneficial in SEM since contrast between the pore space and solid rock is enhanced by the MMA impregnant. 12

22 5 RESULTSOFTHE 14 C-PMMAANALYSIS 5.1 Sample 1 The partition diagram and the autoradiograph of blast sample 1 from tunnel wall are presented in Appendix 1. The porosity profile of sample 1 is summarized from three determined sections (I,II,III) of autoradiograph 1.11/B and it is presented in Figure 5. The long fractures extending to depths of several cm were excluded of the profile measurement. The autoradiograph of rock surface 1.11/B is shown in Figure 6. The exposure time was 32 days. 3.5 ~ z;. u; 0 a... 0 a distance (mm) Figure 5. Porosity profile of sample 1.11/B. Figure 6. Autoradiograph of rock surface 1.11/B. Sample width 98 mm. The autoradiographs of sample 1 showed anomalious dark zones at depths of mm from the blasthole surface. A new autoradiograph shall be made to verify the result. Sample 1 was 57 mm thick. The porosity of the undisturbed matrix was 0.15%. The zone of increased porosity penetrated 13

23 to a depth of 20 mm from the blasthole surface. A great number of fractures were observed and their length varied from a few millimetres to several centimetres, a few seems to penetrate through the matrix (about 6 cm) indicating that the sample length was too short to enable determination of the maximum extent of disturbance. Several fissures parallel to the blasthole surface, at depths of 1 to 3 mm from the disturbed surface, were observed in sample Sample 2 The partition diagram and the autoradiograph of the sample 2 are presented in Appendix 2. The porosity profile of sample 2, which was calculated from sections I and II shown in autoradiograph of the rock surface 2.12/A I, is presented in Figure 7. The autoradiograph of rock surface 2.12/A I is shown in Figure 8. e... ~ ~ c;; a distance (mm) Figure 7. Porosity profile of sample 2.12/ A I. 14

24 Figure 8. Autoradiograph of rock surface 2.12/A I. Sample width 59 mm Sample 2 was 63 mm thick. A piece of rock sample, code 2.111, was broken from the top of the sample before impregnation. The porosity of the undisturbed matrix was 0.20%. The zone of increased porosity penetrated to a depth of 13 mm from the blasthole surface. This zone contains crushed and fractured parts of the disturbance and microfissuration perpendicular to the blasthole surface. A few fractures were observed and their length varied from a few millimetres to a few centimetres, none of them seems to penetrate through the matrix (about 6 cm). A few fissures parallel to the blasthole surface were observed to a depth of 1mm in sample 2. The porosity in the crushed zone at depths of 0 to 7 mm from the disturbed surface was found to be about five times as high as the porosity in undisturbed rock. 5.3 Sample 4 The partition diagram and the autoradiographs of the sample 4 are presented in Appendix 3. The porosity profile of sample 4, which was calculated from sections I and 11 shown in autoradiograph of the rock surface 4.11/B, is presented in Figure 9. The autoradiograph of rock surface 4.11/B is shown in Figure

25 ~ 0.2 ~ "iii a distance (mm) Figure 9. Porosity profile of sample 4.11/B. Figure 10. Autoradiograph of rock surface 4.11/B. Sample width 98 mm Sample 4 was split in two pieces during sample coring along a fracture plane caused by blasting. The first piece was 43 mm thick (4.11, see Appendix 3) and the second one was 36 mm (4.12). The porosity of the undisturbed matrix was 0.15%. The zone of increased porosity penetrated to a depth of 10 mm from the blasthole surface. Two fractures were observed and their length was about 50 mm and they stopped to the end of the sample A few microfissures perpendicular to the blasthole surface were observed and they extended through the sample Several fissures 16

26 parallel to the blasthole surface were observed to a depth of 1-7 mm from the surface in sample 4. A network of fissures could be seen in Fig. 10 at right side of the autoradiograph. 5.4 Sample 7 The partition diagram and the autoradiographs of blast sample 7 from tunnel wall are presented in Appendix 4. The porosity profile of sample 7, which was calculated from sections I, 11 and Ill shown in autoradiograph of the rock surface 7.11 A, is presented in Figure 11. The autoradiograph of rock surface 7.1/A is shown in Figure ~ 0.15 [ distance (mm) Figure 11. Porosity profile of sample 7.11 A. Figure 12. Autoradiograph of rock surface 7.1 I A. Sample width 98 mm 17

27 Sample 7 was 57 mm thick. The porosity of the undisturbed matrix was 0.10%. The zone of increased porosity penetrated to a depth of 15 mm from the blasthole surface. A few microfractures were observed, some of them started from a depth of 10 mm from the blasthole surface and extended to a depth of20-50 mm from the blasthole surface. A few microfissures, which were a few millimetres in length, oriented parallel to the blasthole surface at a depth of 2-5 mm from the surface. The porosity in the disturbed zone to a depth of 2 mm from the blasthole surface was found to be about three times as high as the porosity in undisturbed rock. The total effect of blasting was minor than in samples 1 and Sample 8 The partition diagram and the autoradiographs of the sample 8 are presented in Appendix 5. The porosity profile of sample 8, which was calculated from sections I and 11 shown in autoradiograph of the rock surface 8.11/A, is presented in Figure 13. The autoradiograph of rock surface 8.11/A is shown in Figure ~ 0.2 ~ u; c distance (mm) Figure 13. Porosity profiles of sample 8.11/B. 18

28 Figure 14. Autoradiograph of rock surface 8.11/A. Sample width 98 mm Sample 8 was impregnated in two pieces; 8.11 was 42 mm thick and 8.12 was 90 mm thick. The rock sample 8.12 ended to a natural fracture caused by blasting. The porosity of the undisturbed matrix was 0.05%. The zone of increased porosity penetrated to a depth of 15 mm from the blasthole surface. Two long fractures were observed extending through the rock samples 8.11 and 8.12, thus being 117 mm in length. The aperture of the fractures was about 0.5 mm, which could be seen in visual inspection. Few microfissures, existing both perpendicular and parallel to the blasthole surface were detected and the length of them varied between 5-20 mm. One microfissure, about 30 mm in length, parallel to the blasthole surface was found at a depth of mm from the surface (Fig. 14, right side) The porosity in the disturbed zone at depths of 0 to 2 mm from the blasthole surface was found to be about five times as high as the porosity in undisturbed rock. 5.6 Sample 13 The partition diagram and the autoradiographs of the sample 13 are presented in Appendix 6. The porosity profile of sample 13, which was calculated from sections I, II and Ill shown in autoradiograph of the rock surface 13.1 I A, is presented in Figure 15. The autoradiograph of rock surface A is shown in Figure

29 ~ ~ u; a distance (mm) Figure 15. Porosity profile of sample A. Figure 16. Autoradiograph of rock surface A. Sample width 98 mm Sample 13 was 72 mm thick. The porosity of the undisturbed matrix was 0.15%. The zone of increased porosity penetrated to a depth of 25 mm from the blasthole surface. Two fractures were observed extending perpendicular to the surface. A few micro fissures perpendicular to the blasthole surface were detected and they were 10 to 20 millimetres in length. Several microfractures parallel to the blasthole surface, at 20

30 depths of 0.5 to 1.0 mm from the blasthole surface, were observed in sample 13. The porosity in the disturbed zone to depth of 7 mm from the blasthole surface was found to be about three to five times higher than the porosity in undisturbed rock Sample 14 The partition diagram and the autoradiographs of blast sample 14 from tunnel wall are presented in Appendix 7. The porosity profile of sample 14, which was calculated from sections I, 11 and Ill shown in autoradiograph of the rock surface 14.1 I A, is presented in Figure 17. The autoradiograph of rock surface 14.1/A is shown in Figure ~ 0.5 ~ 'iii c distance (mm) Figure 17. Porosity profiles of sample A. Sample 14 was 60 mm thick. The porosity of the undisturbed matrix was 0.20%. The autoradiographs of sample 14 showed anomalious dark zones at depths of mm from the blasthole surface. A new autoradiograph shall be made to verify the result. Several fractures and fissures were observed extending to depths of mm from the blasthole surface. A few microfissures parallel to the blasthole surface were detected at depths of 1 to 5 mm from the blasthole surface. A pronounced increase in porosity was observed to a depth of 20 mm from the blasthole surface. The positive gradient in the porosity profile of sample 14 at depths of 0 to 4 mm from the blasthole surface is due to 21

31 an experimental error which occurred during sample handling. The tracer was able to evaporate from the pores that were nearest to the surface, before water+mma emulsion surrounded the sample prior to irradiation. Figure 18. Autoradiograph of rock surface A. Sample width 98 mm 22

32 6 RESULTS OF SCANNING ELECTRON MICROSCOPY 6.1 Structure of sample 1 Sample 1. 11/B was sawn following autoradiography according to the partition scheme illustrated in Appendix 1, to obtain the SEM sample 1.11/B II. The sample was mm long and 24 mm wide. The SEM sample included the intact rock matrix as well as the matrix nearest to the blasthole surface. The autoradiograph of surface 1.11/B II is shown in Figure 19. The aperture of the wide micro fracture seen on the top right side of the autoradiograph was analysed being J.lm. In this work the matrix structure of rock adjacent to the blasthole surface was studied. The grain size of the mineral crystals in gneissic tonalite was 1 to 2 mm. The structure of the gneissic tonalite sample was analysed at depths of 0 to 5 mm from the blasthole surface. Figure 19. Autoradiograph of SEM sample 1.11/B II. Sample width mm. Plagioclase, quartz and biotite mineral grains were analysed at depths of 0 to 0. 5 mm from the blasthole surface. The backscattered electron (BSE) images, performed using 200-fold and 500-fold magnifications, are presented in Figures 20, 21 and

33 Figure 20. BSE image of sample 1.11/B at a depth of0.5 mm from the disturbed surface. Plagioclase grain. Magnification 200x. Figure 21. BSE image of sample 1.11/B at a depth of0.5 mm from the disturbed surface. Quartz grain. Magnification 500x. 24

34 Figure 22. BSE image of sample 1.11/B at a depth of 0. 5 mm from the disturbed surface. Biotite grain. Magnification 200x. A great number of intragranular and transgranular fissures were observed in all mineral grains at the depth range of 0-1 mm from the blasthole surface. Plagioclase grains were crushed and wide variation of apertures of fissures were detected; still aperture range being below 20 J..Lm. In quartz grains intragranular fissuration was observed, but the pore apertures were smaller than those in plagioclase grains; being below 5 J..Lm. In biotite the lamellaes were opened and the grain boundaries between biotite and plagioclase or quartz grains were opened. At a depth of 2 mm from the blasthole surface (Figure 23) fissures having apertures several micrometers were observed transsecting plagioclase grains. The plagioclase grain was crushed. The grain boundaries between the minerals were opened, having apertures of few micrometers. 25

35 Figure 23. BSE image of sample 1.11/B at a depth of 2 mm from the disturbed surface. Plagioclase grain. Magnification 1 OOx. A fractured biotite grain is illustrated in Figure 24. The image is at a depth of 5 mm from the blasthole surface and the magnification is 500-fold. The lamellae structure of biotite was not observed to be opened. A few microfractures having apertures of a few micrometers were observed transsecting biotite grains. A few fissures transsecting quartz grains were detected at a depth of 5 mm from the blasthole surface (Figure 25, magnification 200x). Several intra- and transgranular fissures were observed at a depth of 5 mm from the blasthole surface in plagioclase grains (Figure 26, magnification 200x). A clear difference could be seen in the structure of disturbed rock and intact rock. In all minerals the increased fissuration was observed. The structure of intact gneissic tonalite is studied elsewhere (Ref. 7, 13). 26

36 Figure 24. BSE image of sample 1.11/B at a depth of 5 mm from the disturbed surface. Biotite grain. Magnification SOOx. Figure 25. BSE image of sample 1.11/B at a depth of Smm from the disturbed surface. Quartz grain. Magnification 200x. 27

37 Figure 26. BSE image of sample 1.11/B at a depth of 5 mm from the disturbed surface. Plagioclase grain. Magnification 200x. About 10 ~m wide micro fracture transsecting plagioclase grain is shown in Figure 27. The fracture extended as a grain boundary fissure around quartz grain and still between biotite and plagioclase grain. The total length of the fracture was detected to be a few millimetres. The plagioclase matrix is crushed along the fracture. Figure 27. BSE image of sample 1.11/B at a depth of 5 mm from the disturbed surface. Plagioclase grain. Magnification 500x. 28

38 The fracture that was found in the autoradiograph in Fig. 19 was detected using 20 fold magnification in SEM analysis. The total length of the fracture was 25 mm (i.e. part seen in SEM sample). The aperture of the fracture varied between 50 to 200 ~m. The BSE image of the fracture is shown in Figure 28 using 20 fold magnification. Figure 28. BSE image of sample 1.11/B at a depth of 30 mm from the disturbed surface. Magnification 20x. 7 CONCLUSIONS AND DISCUSSION The zone disturbed by blasting was analysed on the basis of samples taken from the walls of the Research Tunnel. MMA was impregnated into the undisturbed and disturbed rock matrix of gneissic tonalite. Differences in recorded with the 14 C-PMMA method. porosity profiles were The results of background porosities and qualitative notes of structure adjacent to the blasthole surface (visual inspection of autoradiographs) measured with the 14 C-PMMA method are presented in Table 2. The porosities of the undisturbed rock matrix ranged from 0.05 to 0.20%. In all blast samples studied, a clear increase in porosities was observed at depths of 0 to 20 mm from the wall surface. The appearance of 29

39 microfractures varied between different blast samples from few detections to a great number of them. Some of them extended to depths of centimetres from the blasthole surface. The microfractures could be visualized also with naked eye from the sawn rock surface. These microfractures were not included in the porosity profiles since the porosity of fractures with an opening of over 20 ~J-m cannot be determined accurately with 14 C-PMMA method. The porosities obtained are lower in the case of existing wide aperture fractures. It is recommended that the total porosities should be measured with other methods and more illustrative parameters should be used to study the fracture density. Table 2. Background porosities and visual inspection of autoradiographs blast sample average background porosity 8% visual inspection of autoradiographs strongly fractured - a great number of microfractures trending to depths of mm from the blasthole surface moderately fractured - several micro fractures 10 to 20 mm in length extending perpendicular to the blasthole surface moderately fractured - a few microfractures perpendicular and parallel to the blasthole surface, 40 to 50 mm in length weakly fractured - few microfractures perpendicular to the blasthole surface, 50 mm in length weakly fractured - two clear microfractures reaching to a depth of 120 mm from the blasthole surface moderately fractured -several fissures about 10 to 20 mm in length strongly fractured -a great number of microfractures a few centimetres in length Several intra- and transgranular fissures were observed in all mineral grains in blast sample 1.11/B at depths of 0 to 5 mm from the disturbed surface. The apertures ranged from a few to several micrometers. 30

40 REFERENCES 1. Hautojarvi, A., Vieno, T., Autio, J., Johansson, E., Ohberg, A.& Salo, J.-P Characterization and tracer tests in the full-scale deposition holes in the TVO Research Tunnel. Geova1'94, Paris, October Autio, J. & Salo, J.-P Boring of the full-scale deposition holes in the TVOresearch tunnel. In. Backblom, G. (ed.), Asp6 Hard Rock Laboratory International Workshop on the Use of Tunnel Boring Machines for Deep repositories, Aspo, June 13-14, Stockholm, Swedish Nuclear Fuel and Waste management Co (SKB), International Cooperation Report Autio, J., Aikas, K. and Kirkkomaki, T Coring and Description of Samples from the Full Scale Experimental Deposition Holes at TVO/Research Tunnel, Nuclear Waste Commission of Finnish Power Companies, Work Report Teka Hautojarvi, A., Ilvonen, M., Vieno, T., Viitanen, P Hydraulic and Tracer Experiments in the TVO Research Tunnel Helsinki, Nuclear Waste Commission of Finnish Power Companies, Report YJT Siitari-Kauppi, M Investigation of Porosity and Microfracturing in a Disturbed Zone with the 14 CPMMA Method Based on Samples from Full-Scale Experimental Deposition Holes of the TVO Research Tunnel, Nuclear Waste Commission of Finnish Power Companies, Report YJT Hellmuth, K.H., Siitari-Kauppi, M. and Lindberg, A Study of Porosity and 14 Migration Pathways 1n Crystalline Rock by Impregnation with C polymethylmethacrylate. Journal of Contaminant Hydrology, 13: Hellmuth, K.H., Lukkarinen, S. and Siitari-Kauppi, M Rock Matrix Studies with Carbon-14-Polymethylmethacrylate (PMMA); Method Development and Applications. Isotopenpraxis Environ. Health Stud., 30: Siitari-Kauppi, M., Lukkarinen, S. and Lindberg, A Study of Rock Porosity by Impregnation with Carbon-14-Methylmethacrylate, Nuclear Waste Commission of Finnish Power Companies, Report YJT Rasilainen, K., Hellmuth, K-H., Kivekas, L., Melamed, A., Ruskeeniemi, T., Siitari Kauppi, M., Timonen, J. & Valkiainen, M An Interlaboratory Comparison of Methods for Measuring Rock Matrix Porosity. Espoo: VTT Energy, VTTRN

41 10. Autio, J., Characterization of the excavation disturbance caused by boring of the experimental full scale deposition holes in the Research Tunnel at Olkiluoto. Report Posiva-96-09, Posiva Oy, Helsinki and similar report in SKB 's (Svensk Kambdinslehantering AB) report series. 11. Autio, J., Kirkkomaki, T Boring of full scale deposition holes using a novel dry blind boring method, POSIVA Autio, J., Aikas, K. and Kirkkomaki, T Coring and description of the samples from the full scale experimental deposition holes and from the walls of the research tunnel at Olkiluoto, Work Report TEKA-96-05e. 13. Siitari-Kauppi, M. and Autio, J., Investigation of Rock Porosity and Microfracturing with 14 C-PMMA mathod. Samples cored from the full-scale experimental deposition holes from the Research Tunnel at Olkiluoto. Posiva Work Report - to be published Daniels, F. and Alberty, R. A Physical Chemistry, Third Edition, John Wiley & Sons, Inc. New York, p 384 (767). 15. Leonard, E. C Vinyl and Diene Monomers, Part 1, A series of Monographs on the Chemistry, Physics, and Technology of High Polymeric Substances, Vol. XXIV, p

42 APPENDICES. APPENDIX 1. Partition diagram of blast sample 1. Appendix la. Autoradiographs of rock surfaces 1.11/B, 1.11/A la, 1.111/A II, 1.112/A II, 1.113/A II and 1.114/A II. APPENDIX 2. Partition diagram of blast sample 2. Appendix 2A. Autoradiographs of rock surfaces 2.12/A la, 2.12/A lib, 2.121/B I, 2.122/B I, 2.123/B I and 2.124/B I. APPENDIX 3. Partition diagram of blast sample 4. Appendix 3A. Autoradiographs of rock surfaces 4.11/B, 4.11/A Ha, 4.111/A I, 4.112/A I, and 4.113/A I. APPENDIX 4. Partition diagram of blast sample 7. Appendix 4A. Autoradiographs of rock surfaces 7.1/B, 7.1/A Ib, 7.11/B II, 7.12/B II, 7.13/B II and 7.14/B II. APPENDIX 5. Partition diagram of blast sample 8. Appendix SA. Autoradiographs of rock surfaces 8.11/A and 8.12/B. APPENDIX 6. Partition diagram of blast sample 13. Appendix 6A. Autoradiographs of rock surfaces 13.1/A, 13.1/B Ha, 13.11/B I, 13.12/B I, 13.13/B I and 13.14/B I. APPENDIX 7. Partition diagram of blast sample 14. Appendix 7A. Autoradiographs of rock surfaces 14.1/A, 14.1/B II, 14.11/B I, 14.12/B I, 14.13/B I and 14.14/B I.

43 APPENDIX 1 INSINOORITOIMISTO ~ SAANIO & RIEKKOLA ov / A /\ 1.11/B ~ 1.11/B I SEM 1.11/B /A la ~ # mm 1.11/B 11 SEM

44 Appendix la 98mm 1.11/B 1.11/A la 1.111/A II (5 mm) 52 mm 1.112/A II (7 mm) 1.113/A 11 (24 mm) 1.114/A 11 (26 mm) Autoradiographs of sample 1. Surfaces according to partition diagram in Appendix 1. Autoradiographs of plane surfaces 1.111/A II, 1.112/A 11, 1.113/A II and 1.114/A II are at depths of 5 mm, 7 mm, 24 mm and 26 mm from blasthole surface (measured from bottom of hole), respectively.

45 APPENDIX2 INSIN66RITOIMISTO m Jl\ SAANIO & RIEKKOLA OY"...I /B / s UJ~ 2.72/A E]~ CD 2.72/8 11 ~,--====;:z;~ 2. 12/B I 0) 2.72/A I 2.72/A 1/b /8 I /8 I /8 I /8 I

46 Appendix 2A 98mm 2.12/A la 2.12/A lib 2.121/B I (6 mm) 47 mm 2.122/B I (13 mm) 2.123/B I (15 mm) 2.124/B I (24 mm) Autoradiographs of sample 2. Surfaces according to partition diagram in Appendix 2. Autoradiographs of plane surfaces 2.121/B I, 2.122/B I, 2.123/B I and 2.124/B I are at depths of 6 mm, 13 mm, 15 mm and 24 mm from blasthole surface (measured from bottom of hole), respectively.

47 APPENDIX 3 INSINOORITOIMISTO._11\ SAANIO & RIEKKOLA ov...1 Fissure Surfaces ClJ 4.72/B I ~ 12/B 4.773/ A I 4.772/ A I 4.777/ A I clip 4.77/A ~t/ I ~ 4.77/A I --\/ ~ 4.72/A 4. 77/B 4.77/ A /la 4.122/B 11 c ~ ) /B If 5. 4.

48 Appendix 3A 98mm 4.11/B 4.11/AIIa 98mm 4.12/A 4.111/A I (5 mm) 42mm 4.113/A I (17 mm) Autoradiographs of sample 4. Surfaces according to partition diagram in Appendix 3. Autoradiographs of plane surfaces 4.111/ A I and 4.113/ A I are at depths of 5 mm and 17 mm from blasthole surface (measured from bottom of hole), respectively.

49 APPENDIX4 INSINOORITOIMISTO Jll\ SAANIO & RIEKKOLA ov ~ I Q n~a 0 ~ D 7.1/A lb 7.1/A 11 //j~ :; [(.',',,...,,...,,.,,.,.... )v,.. ~ '.,., ',,,,', ',,,,,.'..! mm 7.14/A /A /A 11!.~mm fd 7.11/ A 11

50 Appendix 4A 98mm 7.1/B 7.1/A Ib 7.11/A 11 (5 mm) 45 mm 7.12/A 11 (16 mm) 7.14/A II (35 mm) Autoradiographs of sample 7. Surfaces according to partition diagram in Appendix 4. Autoradiographs of plane surfaces 7.11/A II, 7.12/A II, 7.13/A II and 7.14/A II are at depths of 5 mm, 16 mm, 18 mm and 35 mm from blasthole surface (measured from bottom of hole), respectively.

51 APPENDIXS INSINCCRITOIMISTO.,n SAANIO & RIEKKOLA ov I I \~ 8.3 ( / / / \ \ \ 8.21/B 8.12/A 8.12/8 8.11/8 (] 8/ \ ~ 8. 11/B I []i 8.11/B 11 /1 \ /8 I I # /8 I mm 8.111/8 I

52 Appendix SA 98mm 8.11/A 8.12/B Autoradiographs of sample 8. Surfaces according to partition diagram in Appendix 5.

53 APPENDIX6 INSINOORITOIMISTO ""' SAANIO & RIEKKOLA OY~...I A 13.1/B I 13.1/8 /la /8 I mm 73.13/8 I I I

54 Appendix 6A 98mm 13.1/A 13.1/B Ila 13.11/B I (2 mm) 54 mm 13.12/B I (4 mm) 13.13/B I (27 mm) 13.14/B I (29 mm) Autoradiographs of sample 13. Surfaces according to partition diagram in Appendix 6. Autoradiographs of plane surfaces 13.11/B I, 13.12/B I, 13.13/B I and 13.14/B I are at depths of 2 mm, 4 mm, 27 mm and 29 mm from blasthole surface (measured from bottom of hole), respectively.

55 APPENDIX 7.,n SAANIO & RIEKKOLA ov...1 INSIN66RITOIMISTO /A 14.1/8 I # # /8 I 14.13/8 I /8 I, l~ l, 5 mm 14.11/8 I

56 Appendix 7A 98mm 14.1/A 14.1/B IIa 14.11/B I (5 mm) 45 mm 14.12/B I (33 mm) 14.13/B I (35 mm) 14.14/B I (45 mm) Autoradiographs of sample 14. Surfaces according to partition diagram in Appendix 7. Autoradiographs of plane surfaces 14.11/B I, 14.12/B I, 14.13/B I and 14.14/B I are at depths of 5 mm, 33 mm, 35 mm and 45 mm from blasthole surface (measured from bottom of hole), respectively.