Strength and Strain Anisotropy of Olkiluoto Mica greiss · Olkiluoto Mica greiss. Matti Hakala KMS...

P O S I V A O Y

FI -27160 OLKILUOTO, F INLAND

Tel +358-2-8372 31

Fax +358-2-8372 3709

Matt i Haka la

Har r i Kuu la

John Hudson

October 2005

Work ing Repor t 2005 -61

Strength and StrainAnisotropy of

Olkiluoto Mica greiss

Matt i Haka la

KMS Haka l a Oy , F i n l and

Har r i Kuu la

Rock Eng inee r i ng Depa r tmen t ,

He l s i nk i Un i ve rs i t y o f Techno logy , F i n l and

John Hudson

Impe r i a l Co l l ege and

Rock Eng inee r i ng Consu l t an ts , UK

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.

October 2005

Base maps: ©National Land Survey, permission 41/MYY/05

Work ing Repor t 2005 -61

Strength and StrainAnisotropy of

Olkiluoto Mica gneiss

STRENGTH AND STRAIN ANISOTROPY OF OLKILUOTO MICA GNEISS ABSTRACT An anisotropy in the elastic moduli values of intact rock with a ratio of more than 1.3~1.5 has been reported to have an effect on the calculated magnitudes and orientations of the in situ principal stress components as measured by the overcoring method. Work related to the on-going site investigation for a deep radioactive waste repository at the Olkiluoto site in Western Finland has shown that the migmatic mica gneiss is anisotropic which could therefore affect the interpretation of overcoring stress measurement results. This paper includes a summary of the theory of anisotropy concerning the intact rock moduli via the strain compliance matrix, a description of the core sample testing methods, and interpretation of results for the migmatic mica gneiss from two site investigation boreholes. In this case study, 19 specimens were tested and the results showed a modulus anisotropy of about 1.4. Because such anisotropy is high enough to produce significant errors in the estimation of the in situ principal stresses, it is recommended to take this into account in the interpretation of the stress measurement results, both in the context of the current work in Finland and in other projects where similar anisotropy is encountered. Keywords: anisotropy, elastic parameters, in situ rock stress, overcoring, quality control, laboratory testing, Olkiluoto

OLKILUODON KIILLEGNEISSIN MUODONMUUTOS- JA LUJUUSANISOTROPIA TIIVISTELMÄ Ehjän kiven kimmo-ominaisuuksien anisotrooppisuuden tiedetään vaikuttavan irtikairausmenetelmällä tehdyn in situ jännitystilamittauksen tulkintaan, jos anisotropia-aste on yli 1.3 tai 1.5. Olkiluodon migmaattisen kiillegneissin on tiedetty olevan anisotrooppinen, mutta anisotropia-asteen määrityksen merkitys tuli korostetusti esille Posivan aiemmassa ”Irtikairausjännitystilamittausten laadunvarmistus”-projektissa. Tässä työssä on esitetty muodonmuutosanisotropiamallin teoria, kuvattu määritysmenetelmä, sekä esitetty kairarei’istä KR12 ja KR14 valittujen 19 tyypillisen Olkiluodon migmaattisen kiillegneissinäytteen testitulokset ja niiden tulkinta. Tulosten perusteella migmaattisen kiillegneissin muodonmutosanisotropia-aste (E/E’) on luokkaa 1.4, mikä on riittävän suuri vaikuttamaan tulkitun jännitystilan suuruuteen ja suuntaan. Tulosten perusteella suositellaan anisotroooppisen tulkinnan kehittämistä ja huomioimista jännitystilamittausten tulostulkinnassa. Avainsanat: anisotropia, kimmoiset parametrit, in situ jännitystila, irtikairaus, laadunvarmistus, laboratoriotestaus, Olkiluoto

1

ABSTRACT

TIIVISTELMÄ

CONTENT 1

FOREWORD 3

1 INTRODUCTION 5 1.1 Background 5 1.2 Scope of the work 5

2 ROCK ANISOTROPY AND INTERPRETATION OF TEST RESULTS 7 2.1 Theory of Rock Anisotropy 7 2.2 Interpretation of test results 12

3 TEST SPECIMENS 21 3.1 Selection of samples 21 3.2 Specimen handling procedure 24

4 TEST CONFIGURATIONS AND PROCEDURES 27 4.1 Testing devices 27

4.1.1 MTS 815 Rock mechanics testing system 27 4.1.2 Strain gage measuring system 28 4.1.3 Acoustic emission (AE) measuring system 29

4.2 Uniaxial compression tests 31 4.3 Indirect Brazilian tensile tests 35 4.4 Quality control 38

5 TEST RESULTS 41 5.1 Stress-strain behaviour 41 5.2 Elastic parameters 42 5.3 Strength parameters 48

6 CONCLUSIONS, discussion and recommendations 57

REFERENCES 61

APPENDICES 65

3

FOREWORD

The work reported in this paper was carried out under contract to Posiva Oy of Finland, in co-operation with SKB AB of Sweden. The following organizations and persons participated in the project: Rolf Christianson (SKB); Pekka Eloranta and Harri Kuula (Helsinki University of Technology); Matti Hakala (KMS Hakala); Heikki Hinkkanen (Posiva); John A. Hudson (Rock Engineering Consultants); Erik Johansson (Saanio & Riekkola Oy); and Jonny Sjöberg (SwedPower). The authors are grateful to Posiva and SKB for their continuing support of the project.

5

1 INTRODUCTION

1.1 Background A rock stress estimation campaign is currently underway at the anticipated site of a radioactive waste repository on the west coast of Finland at Olkiluoto. The dominant rock type is migmatic mica gneiss; this rock type is clearly foliated (Vaittinen et al. 2003) and thus expected to have anisotropic deformation and strength behaviour. Such anisotropy has been reported to have an effect on the interpretation of in situ stress measurements undertaken by the overcoring method. Amadei (1996) concluded that an elastic modulus anisotropy ratio of 1.5 can introduce a 33% error in the calculated magnitudes of the principal stresses while Worotnicki (1993) concluded that modulus anisotropy below 1.3 to 1.5 does not produce a significant error in the interpreted principal stresses. However, a study based on Amadei’s 1983 results indicates that an anisotropy ratio of between 1.14 to 1.33 will have a definite effect on the interpreted in situ state of stress and thus such anisotropy should be taken into account, assuming that the elastic parameters of the rock at the stress measurement location can be determined with sufficient accuracy. Large number of tests for Olkiluoto migmatic mica gneiss have been conducted previously (Hakala & Heikkilä 1997a and 1997b). The anisotropic elastic parameters could not be defined based on these test results because these had not been obtained utilising the specific criteria for anisotropy testing sample selection; also, the test instrumentation for anisotropy testing differs from conventional testing. Moreover, samples from previous testing programmes mostly has a limited range of sample foliation angles.

1.2 Scope of the work The aim of this study, which was conducted within the context of in situ rock stress estimation, was to define the range of elastic modulus and strength anisotropy variation of the Olkiluoto migmatic mica gneiss in order to provide information on whether to continue the development work of the project “Quality Control for Overcoring Stress Measurement Data” (Hakala 2005, in prep). Such quality control has been recognised in the relevant ISRM Suggested Methods to be a crucial component of stress estimation programmes ( Christiansson & Hudson 2002). The test methods described here and involving uniaxial loading tests and indirect tesile tests are based on Hakala & Heikkilä (1997b); the sample selection and strain gauge instrumentation techniques on Amadei (1996). The specimens selected to represent typical Olkiluoto migmatic mica gneiss conditions were taken from boreholes OL-KR12 and OL-KR14 at the Olkiluoto site.

6

Following a brief review of rock anisotropy, the selection of the specimens and the test configurations, procedures and results are described. The conclusions and recommendations include discussion of the results in terms of how the foliation anisotropy has different effects on the crack initiation, crack damage, and peak strength, and the necessity of incorporating significant anisotropy in a stress estimation interpretation programme.

7

2 ROCK ANISOTROPY AND INTERPRETATION OF TEST RESULTS

2.1 Theory of Rock Anisotropy The following description of rock anisotropy is abstracted from Amadei's 1996 Schlumberger Lecture Award paper: Importance of Anisotropy When Estimating and Measuring in Situ Stress in Rock (Amadei B. 1996). In the context of the current work, Amadei’s paper describes rock anisotropy so thoroughly that other references are not necessary. According to Amadei (1996) many rocks exposed near the Earth’s surface show well defined fabric in the form of bedding, stratification, layering, foliation, fissuring or jointing. These rocks can then have properties (physical, dynamic, thermal, mechanical, hydraulic) that vary with direction and are thus inherently anisotropic. This anisotropy can be found at different scales in a rock mass ranging from the anisotropic microstructure of intact laboratory-sized specimens to the anisotropic faulting and fracturing geometry of an entire rock mass. In terms of the unfractured rock, anisotropy is a characteristic of intact foliated metamorphic rocks (slates, gneisses, phyllites, schists). In these rocks, the fabric can be expressed in different ways. Closely-spaced fractures termed cleavages are found, for instance, in slates and phyllites. These rocks tend to split into planes due to the parallel orientation of microscopic grains of mica, chlorite or other platy minerals. In schists, the fabric is created by the parallel to sub-parallel arrangement of large platy minerals such as mica, chlorite and talc. Foliation can also be expressed in the form of alternating layers of different mineral composition such as in gneisses (Milnes et al. 2005). Non-foliated metamorphic rocks, such as marble, can also show some anisotropy due to the preferred orientation of calcite grains. Anisotropy is also a characteristic of intact laminated, stratified or bedded sedimentary rocks, such as shales, sandstones, siltstones, limestones, coal, etc. Here, the anisotropy results from complex physical and chemical processes associated with the transportation, deposition, compaction, cementation, etc. It is noteworthy that rocks which have undergone several formation processes may contain more than one direction of planar anisotropy − such as the foliation and bedding planes in slates; furthermore, these directions are not necessarily parallel to each other. Also, linear features such as lineations can be superposed on the planar features. Rock mass anisotropy can also be found in volcanic formations (basalt, tuff) and sedimentary formations consisting of alternating layers or beds of different (isotropic or anisotropic) rock types. Rock masses cut by one or several regularly spaced joint sets are anisotropic in addition to being discontinuous, with the rock between the joints being either isotropic or anisotropic. It is not unusual to have several types of planar anisotropy in a rock mass: e.g. joints and foliation planes, or joints and bedding planes.

8

If the joints develop parallel to the foliation or bedding planes, they can be termed foliation joints or bedding joints, respectively. The directional character of the deformability properties of anisotropic rocks and rock masses is usually assessed by field and laboratory testing, possibly supported by numerical modeling. Deformability test results on anisotropic rocks are commonly analyzed in terms of the theory of elasticity for anisotropic media by using the generalized form of Hooke’s law. Expressed via the compliance matrix, the rock then has 36 elastic constants of which 21 are independent. However, for most practical cases, anisotropic rocks are modeled as transversely isotropic (five constants) or orthotropic (nine constants) media within a co-ordinate system attached to their structure or directions of symmetry. Transverse isotropy implies that at each point in the rock there is an axis of rotational symmetry and that the rock has isotropic properties in the plane normal to that axis, this plane being the plane of transverse isotropy. Orthotropy (orthorhombic symmetry) implies that three orthogonal planes of elastic symmetry exist at each point in the rock and that these planes have the same orientation throughout the rock. For a rock mass that is orthotropic in a local n, s, t Cartesian coordinate system (Figure 2-1) attached to clearly defined planes of anisotropy, the generalized Hooke’s law can be expressed as follows (Equations 2-1 and 2-2):

Figure 2-1. Orthotropic rock with three planes of symmetry normal to the n, s, t directions (from Amadei B. 1996).

9

⎥⎥⎥⎥⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢⎢⎢⎢⎢

⎣

⎡

⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢

⎣

⎡

−−

−−

−−

=

⎥⎥⎥⎥⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢⎢⎢⎢⎢

⎣

⎡

ns

nt

st

t

s

n

ns

nt

st

ts

st

n

nt

t

ts

sn

ns

t

tn

s

sn

n

ns

nt

st

t

s

n

G

G

G

EEE

EEE

EEE

τττσσσ

νν

νν

νν

γγγεεε

100000

010000

001000

0001

0001

0001

(2-1)

or in compact matrix form

nstnst σHε = (2-2) Thus, nine independent elastic constants are needed to describe the elasticity of the medium in the n, s, t coordinate system: En, Es and Et are the Young’s moduli in the n, s and t (or 1, 2 and 3) directions, respectively; Gns Gnt and Gst are the shear moduli in planes parallel to the ns, nt and st planes, respectively; finally, νij (i,j = n, s, t) are the Poisson’s ratios that characterize the normal strains in the symmetry directions j when a stress is applied in the symmetry directions i. Because of the symmetry of the compliance matrix H determined from energy considerations, the Poisson’s ratios νij and νji are such that νij/Ei = νji/Ej. This orthotropic formulation has been used in the literature to characterize the deformability of rocks such as coal, schists, slates, gneisses, granites and sandstones. For instance, the cleat and bedding planes of coal are often assumed to be planes of elastic symmetry. Equations (1) and (2) still apply if the rock is transversely isotropic in one of the three ns, nt or st planes of Figure 2-1. However, in this case, only five independent elastic constants are required to describe the deformability of the rock in the n, s, t coordinate system. In this paper, these constants are termed E, E′, ν, ν ′ and G′ with the following definitions: - E and E′ are Young’s moduli in the plane of transverse isotropy and in the direction

normal to it, respectively, - ν and ν′ are Poisson’s ratios characterizing the lateral strain response in the plane

of transverse isotropy to a stress acting parallel or normal to it, respectively, - G′ is the shear modulus in planes normal to the plane of transverse isotropy.

10

Relations exist linking E, E′, ν, ν ′, G and G′ and the coefficients of matrix H in equations (2-1) and (2-2). For instance, for transverse isotropy in the st plane ( Equation 2-3 ):

GGGEEEEE nsnstsn ′====

′=

111;111;11

EGEEEEEE stt

ts

s

st

n

nt

n

ns )1(21;; υυυυυυυ +===

′′

== (2-3)

The transverse isotropy formulation has been used to characterize the deformability of rocks such as schists, gneisses, phyllites, siltstones, mudstones, sandstones, shales and basalts. For such rocks, the plane of transverse isotropy is assumed to be parallel to the foliation, schistosity or bedding planes. Note that some of the five or nine elastic constants of the specific anisotropic configurations are sometimes assumed to be related. For instance, for transversely isotropic rocks, the modulus G′ is often expressed in terms of E, E′, ν and ν′ through the following empirical equation:

EEEG ′′

+′

+=′

υ2111 (2-4)

Naturally, this is theoretically incorrect because the five elastic constants are independent; however, the equation has been found to be a useful engineering approximation. For orthotropic rocks, the shear moduli Gns, Gnt and Gst are related to the three Young’s modulus and Poisson’s ratios. These relations were first introduced by Saint-Venant (1863). In a survey of elastic constants of anisotropic rocks, Worotnicki (1993) concluded that most of the published experimental data support the validity of the Saint-Venant approximation, with some major exceptions. Martino and Ribacchi (1972) also found that the empirical relations are not always acceptable for many rocks. The five and nine elastic properties of transversely isotropic and orthotropic rocks, respectively, cannot be any set of values; indeed, some inequalities (associated with the thermodynamic constraints that the rock strain energy remains positive definite) must be satisfied. For instance, for transverse isotropy, the five elastic properties E, E′, ν, ν′, G and G′ must satisfy the following thermodynamic constraints:

0,, >′′ GEE (2-5)

11 <<− υ (2-6)

11

( ) ( )2

12

1 υυυ −⋅

′<′<

−⋅

′−

EE

EE

(2-7)

Equations (6) and (7) reduce to - 1 < ν < 0.5 if the rock is isotropic, for which E = E′, G = G′ and ν = ν ’. For orthotropy, the expressions for the thermodynamic constraints on the nine elastic properties are more complex and can be found in Amadei et al. 1987. In general, intact rocks are not too strongly anisotropic compared to other engineering materials such as wood or composites. However, Amadei et al. (1987) analyzed 98 measurements of elastic properties and found that for most intact transversely isotropic rocks, the ratio E/E′ varies between 1 and 4. Several cases of rocks with E/E′ less than unity were found, but the ratio did not fall below 0.7. The ratio G/G′ was found to vary between 1 and 3; the Poisson’s ratio, ν, between 0.1 and 0.35; and v′’E/E′ between 0.1 and 0.7. In a more recent paper, Worotnicki (1993) classified anisotropic rocks into four groups as follows. - Quartzofeldspathic rocks (e.g. granites; quartz and arkose sandstones, granulites and

gneisses). - Basic/lithic rocks (e.g. basic igneous rocks such as basalt; lithic and greywacke

sandstones and amphibolites). - Pelitic (clay) and pelitic (micas) rocks (e.g. mud-stones, slates, phyllites and

schists). - Carbonate rocks (e.g. limestones, marbles and dolomites). Based on 200 sets of test results, Worotnicki (1993) concluded that quartzofeldspathic and basic/lithic rocks show low to moderate degrees of anisotropy with a maximal to minimal Young’s modulus ratio Emax /Emin less than 1.3 for about 70% of the rocks analyzed and less than 1.5 in about 80%. This ratio was found not to exceed 3.5 (Figure 2-2a). Pelitic clay and pelitic mica rocks show the highest degree of anisotropy with Emax/Emin less than 1.5 for about 33% of the rocks analyzed and less than two in about 50%. The modulus ratio was found not to exceed six, with most cases below four (Figure 2-2b). Finally, carbonate rocks were found to show an intermediate degree of rock anisotropy with Emax/Emin not exceeding 1.7 (Figure 2-2c).

12

Figure 2-2. Histograms of Emax/Emin ratios for: (a) quartzofeldspathic and basic/lithic rock; (b) pelitic clay and pelitic mica rocks; and (c) carbonate rocks (from Worotnicki 1993).

2.2 Interpretation of test results In the following text, the interpretation methods used to determine elastic parameters, critical stress states and damage from the stress-strain data are described. Interpretation of the same critical stress states from the acoustic emission measurement results is also given. Before interpretation, the axial and the radial stress strain curves are replaced with Fourier transformations to filter the noise and, in this way, to reduce the effect of subjective selection. The strain gage values are average values from four rosettes.

13

Apparent elastic parameters For all uniaxial compression test specimens, the elastic parameters, Young’s modulus (E) and Poisson’s ratio (ν), were established. This was achieved as secant values from the range of -0.01% radial strain (εr) to half of the peak strength (σp) (Figure 2-3). The range was changed only if the axial or radial stress-strain behavior was clearly non-linear within this range. The definition of the determination limits is presented in Hakala (1996). Anisotropic elastic parameters The type of loading test and the number of tests required to determine the elastic constants of a given rock depend largely on the degree and type of symmetry assumed for the rock. Consider for example a transversely isotropic rock sample tested under uniaxial compression (Fig. 2-4). An x, y, z coordinate system is attached to the specimen with the z axis parallel to the plane of transverse isotropy dipping at an angle θ with respect to the xz-plane. The rock is transversely isotropic in the st-plane of Fig. 2-4 and has five elastic properties E, E′, v, v’ and G′ as defined in equation (1-3). Strains are measured in the x, y and z directions using strain gages.

Axial Stress( MPa )

20

40

60

80

100

120

-0.10 0.0 0.10 0.20

Radial Strain ( % ) Axial Strain ( % )

σp

σcd

σci

Lower limit= -0.01 %ε r

Upper limitσp / 2

∆ε r ∆εa

∆σa

E =

ν ∆ε r∆εa

∆σa∆εa

= -

Figure 2-3. Determination of the elastic parameters in the uniaxial test.

14

Figure 2-4. Transversely isotropic rock sample tested under uniaxial compression (from Amadei 1996). The following presentation relating to the calculation of the elastic parameters for a transversely isotropic rock is taken from Amadei’s (1996) paper: Importance of Anisotropy When Estimating and Measuring in Situ Stress in Rock . Using the theory of elasticity for anisotropic media and assuming uniform stresses and strains in the test specimen, the strains εx, εy, εz and γxy can be related to the applied stress, σ, as follows

σγσεσεσε 26232212 ;;; aaaa xyzyx ==== (2-8) with

⎟⎠⎞

⎜⎝⎛

′−

′++

′′

−′′

−=GEEEE

a 1114

2sincossin2

4412

θθνθν

⎟⎠⎞

⎜⎝⎛

′′

−′

+−′

=EGEE

a νθθθ 214

2sinsincos 244

22

θνθν 2sincos 2223 EE

a −′′

−= (2-9)

GEEEEa

′−⎥

⎦

⎤⎢⎣

⎡⎟⎠⎞

⎜⎝⎛

′′

+−⎟⎠⎞

⎜⎝⎛

′′

+′

=2

2cos2sin1sin1cos2sin 2226

θθνθνθθ

15

Equations (2-8) and (2-9) can also be used to calculate the apparent Young’s modulus, Ey and apparent Poisson’s ratios νyx and νyz of the rock in the x, y, z coordinate system with

22

23

22

12

22

;;1aa

aa

aE yzyxy −=−== νν

(2-10) These three quantities depend on the angle θ. By conducting uniaxial compression tests on three specimens cut at different angles with respect to the plane of transverse isotropy, the five elastic properties of the rock can theoretically be determined from the linear portion of the corresponding stress-strain curves. In Fig. 2-5, three specimens of the same rock are tested in uniaxial compression with θ = 0°, θ = 90° and an inclined angle θ different from 0° or 90°. Using equations 2-8 and 2-9, the strains measured on the first specimen (Fig. 2-5a) allow the determination of E′ and v′; whereas those on the second specimen (Fig. 2-5b) are used to determine E and v. The strains measured on the third specimen (Fig. 2-5c) are used to determine the shear modulus G′. A procedure that has been found by Amadei (1996) to work well is to instrument each of the three specimens in Fig. 2-5 with two to four 45° strain rosettes. All strain measurements are then analyzed simultaneously. Let N be the total number of strain measurements (with N > 5) for all three specimens in Fig. 2-5. According to equations 2-8 and 2-9, each strain measurement is linearly related to the five unknown compliances l/E, l/E′, v/E, v′/E′ and l/G′. In matrix form, the strain measurements can then be expressed in terms of the five compliances as follows [ ] [ ][ ]CT=ε (2-11) where [ε] is a (N x 1) matrix of strain measurements, [T] is a (N x 5) matrix and [C] = (l/E l/E′v/E v/E′ l/G′). Equation 2-11 is then solved for the least squares (best fit) estimate of the five compliance terms by multi-linear regression analysis. The advantage of this approach is that all strain measurements are taken into account when determining the compliance terms. Furthermore, the method can be extended to more than three specimens.

16

Figure 2-5. Three specimens of a transversely isotropic rock tested in uniaxial compression with: (a) θ=0°, (b) θ=90°and (c) θ≠0° and 90° (from Amadei 1996).

17

Critical stress states The ‘critical stress states’ term here refers to tensile strength (σt), crack initiation stress (σci), crack damage stress (σcd) and peak strength (σp) (Figure 2-6). In addition to these stress values, the corresponding axial and radial strains are also recorded.

Axial Stress( MPa )

20

40

60

80

100

120

-0.15 -0.10 -0.05 0.05 0.10 0.20 0.250.15Radial Strain ( % ) Axial Strain ( % )

Elastic region II

Unstable crack IVgrowth

Stable crack IIIgrowth

Crack closure I

Onset of post-peak region V - temporary hardening

Crack Damage Stress- true peak strength

σcd

Crack Initiation Stress- begining of damage

σci

-0.15

-0.10

-0.05

0

0.05

0.10

0.0 0.05 0.10 0.15 0.20

VolumetricStrain ( % )

0.25

Axial Strain ( % )

I

IIIII IV

Crack Closure Calculated CrackVolumetric Strain

Measured totalvolumetric strain

New Crack Volume

Axial StressAxial Strain

RadialStrain

Natural Microcracks

Peak Strength σp

Tensile Strength σt

Figure 2-6. Specification of critical stress states σt , σci , σcd and σp.

18

The tensile strength (σt) is defined as the ultimate tensile stress capacity of any indirect tensile test and specifically here from the compressive load of the indirect Brazilian test (Equation 2-12) (ISRM 1986). The corresponding axial and radial strains cannot be defined from the results of the indirect tensile test.

σπt

FDL

=2

(2-12) where F is maximum axial load ( N )

D specimen diameter ( m ) L specimen length ( m )

The crack initiation stress is defined as the stress level where the crack volumetric strain (εv,cr) deviates from zero (Figure 2-6) (Martin 1994). The crack volumetric strain (εv,cr) is calculated by subtracting the elastic deformations (εv,e) of the rock matrix from the measured total volumetric strain (εv) (Equation 2-13). The elastic volumetric strain (εv,e) is defined by Young’s modulus (E) and Poisson’s ratio (ν) and the values of major (σ1) and minor principal stresses (σ3) (Equation 2-14).

eVVcrV ,, εεε −= (2-13)

ε ν σ σv e E, ( )=−

−1 2

1 3 (2-14)

After subtracting the elastic volumetric strain (εv,e) from the total volumetric strain (εv), the crack volumetric strain curve is shifted so that the maximum value is zero (Figure 2-6). The determination of the crack initiation stress (σci) state is not always clear; therefore, the first guess for σci is determined as the last point having a crack volumeric strain (εv,cr) equal to 0.5% of the total compaction (Figure 2-7a). This value, checked visually, is at the intersection of the horizontal line and the extension of the increasing crack volume (Figure 2-7b). The crack damage stress (σcd) is defined in the uniaxial test as the reversal of the volumetric strain (εv) curve (Figure 2-6) (Martin 1994). At this point, the total volume of the specimen changes from compaction to dilation. The total volumetric strain (εv) is approximated from the measured axial (εa) and radial strains (εr) as ε ε εv a r= + 2 (2-15) The peak strength (σp) is defined as the highest observed axial stress (Figure 2-6).

19

Axial Stress ( MPa )

Crack Volumetric Strain ( % )

-0.01 %

0.00 %

0.01 %

0 20 40 60 80

Fast Fourier Transformation,n=10

Measured Data


Crack Volumetric Strain ( % )

-0.01 %

0.00 %

0.01 %

0 20 40 60 80

Visual Trend Lines

Measured Data

Crack Initiation Stress as Intersectionof Visual Trend Lines

Crack Initiation Stress as Last ZeroValue of Fourier Tranformation

a.

b.

Figure 2-7. Determination of the crack initiation stress (σci) as the first non-zero point of the fitted crack volumetric curve (a), or as an intersection point of the visual trend lines (b).

Acoustic emission (AE) The critical stress states of crack initiation (σci) and crack damage (σcd) were also defined from cumulative AE count results. In an ideal AE result for mica gneiss, the following can be separated: a) the emission caused by load application; b) the elastic region; c) the initiation of microcracking; d) the onset of stable microcracking; e) the beginning of unstable microcracking (Figure 2-8). Primarily, the initiation of microcracking is interpreted as being directly associated with the crack initiation stress

20

(σci) but, if the microcracking starts irregularly, being minor, then the onset of stable microcracking is used instead. The beginning of unstable microcracking, where the cumulative count - axial stress relation changes from linear to exponential, is defined as the crack damage stress (σcd). In some cases, the elastic part is missing and the interpretation of the crack initiation stress becomes inaccurate or subjective. In order to see the strength of AE events, the cumulative count result is also divided into bands according to maximum amplitude (Figure 4-6 and 2-8).

Crack Initiation of micro-crack majority,


0

250

500

0

2500

5000

0 20 40 60 80 100 120 140 160 180

Crack Initiationof favourablemicrocracks

Microcracking increaselinearly with increase ofaxial stress

The beginning ofthe elastic region

Amplitude Pand ( V )> 9 8 - 9 7 - 86 - 7 5 - 6 < 5Total

Accumulative Counts in Amplitude Bands Total Accumulative Counts

750

1000

1250

1500

7500

10000

12500

15000

The beginning of unstable cracking,Crack damege,

Exponential increaseof microcracking aftercrack damage

σcd

σci

Unloading /Reloading

Figure 2-8. Interpretation of critical stress states from AE results.

21

3 TEST SPECIMENS

The following section describe the whole specimen handling procedure from the core drilling to loading in the laboratory.

3.1 Selection of samples The studied specimens were from the boreholes OL-KR12 and OL-KR14 of Posiva’s Olkiluoto investigation site (Figure 3-1 and Figure 3-2). The 795 m long borehole OL-KR12, with a diameter of 56 mm, was drilled in the winter of 2000. The main rock types encountered in OL-KR12 are migmatitic mica gneiss, granite and tonalite (Niinimäki 2000). The 514 m long borehole OL-KR14, with a diameter of 76 mm, was drilled in the spring of 2001. The main rock types encountered in OL-KR14 are migmatitic mica gneiss, granite and tonalite (Niinimäki 2001). The diameter of the drilled core sample was 42 mm in OL-KR12 and 52 mm in OL-KR14. At the end of the field work the core samples were transferred to the outdoor temperature storage of the Geological Survey of Finland at Loppi.

EurajokiOlkiluoto

100 km

Figure 3-1. Location of the Olkiluoto investigation site in Finland.

FINLAND

22

Figure 3-2. The Olkiluoto island site and the location of boreholes OL-KR12 and OL-KR14. After detailed geological inspection, the core samples for this study were selected by Jorma Palmen (Fintact Oy) and Matti Hakala (KMS Hakala Oy) and transferred to the Laboratory of Rock Engineering (LRE) at Helsinki University of Technology (HUT). Specimens where the dip of the foliation was under 20° or over 75° were difficult to find because of the orientation of the in situ foliation versus the borehole orientation. Before selection of the core samples for specimen preparation, the cores of both depth regions were carefully inspected visually to avoid pre-existing joints. No color penetration examination was used. Before the specimen preparation, the core samples were stored in warm storage room conditions with an average temperature of 22ºC and with 30% - 40% air humidity. Selected specimens with their dimensions after sawing and grinding are listed in Table 3-1.

23

Table 3-1. Test specimens (with the dip of foliation being measured from the plane perpendicular to borehole axis).

Test type Borehole Depth

( m ) dip of

foliation(° )

Dimensions ( mm )

Parallellism ( mm )

Length /Diam. ratio

Density(kg/m3)

Length Diam. end sides Uniaxial test OLKR14 333.11 0 129.37 51.49 0.01 0.30 2.51 2720 Uniaxial test OLKR14 334.14 10 129.48 51.41 0.02 0.40 2.52 2742 Uniaxial test OLKR12 556.79 15 105.96 41.53 0.01 0.50 2.55 2791 Uniaxial test OLKR12 535.14 20 105.93 41.03 0.01 0.30 2.58 2752 Uniaxial test OLKR12 523.97 22 105.95 41.52 0.02 <0.05 2.55 2756 Uniaxial test OLKR12 551.81 25 103.57 41.62 0.03 - 2.49 2749 Uniaxial test OLKR12 485.08 27 105.68 41.59 0.01 0.05 2.54 2734 Uniaxial test OLKR12 485.31 27 103.56 41.61 0.03 0.05 2.49 2744 Uniaxial test OLKR12 493.88 27 105.67 41.12 0.01 0.15 2.57 2766 Uniaxial test OLKR12 403.68 42 105.70 42.67 0.01 0.60 2.48 2630 Uniaxial test OLKR12 574.44 42 106.17 42.33 0.01 0.05 2.51 2623 Uniaxial test OLKR12 404.10 45 103.59 41.51 0.04 0.30 2.50 2763 Uniaxial test OLKR12 404.21 45 106.03 41.52 0.02 0.50 2.55 2770 Uniaxial test OLKR12 573.02 45 103.56 41.42 0.04 0.05 2.50 2774 Uniaxial test OLKR12 400.26 70 103.50 41.54 0.03 0.15 2.49 2756 Uniaxial test OLKR12 619.01 70 103.50 41.23 0.03 0.40 2.51 2716 Uniaxial test OLKR12 619.15 70 106.18 41.20 0.01 0.60 2.58 2728 Uniaxial test OLKR12 619.75 78 103.50 41.34 0.03 0.30 2.50 2840 Uniaxial test OLKR12 618.48 80 103.40 41.27 0.02 0.40 2.51 2724 Brazil test OLKR14 333.24 0 25.98 51.36 - - 0.51 2698 Brazil test OLKR14 333.29 10 26.65 51.48 - - 0.52 2682 Brazil test OLKR12 556.65 15 21.51 41.65 - - 0.52 2758 Brazil test OLKR12 524.08 22 20.68 41.50 - - 0.50 2744 Brazil test OLKR12 551.92 25 20.44 41.65 - - 0.49 2798 Brazil test OLKR12 485.19 27 21.03 41.61 - - 0.51 2718 Brazil test OLKR12 485.41 27 20.84 41.61 - - 0.50 2746 Brazil test OLKR12 493.80 27 20.88 41.02 - - 0.51 2773 Brazil test OLKR12 403.79 42 21.31 41.52 - - 0.51 2750 Brazil test OLKR12 574.55 42 20.67 41.40 - - 0.50 2747 Brazil test OLKR12 404.39 45 20.60 41.53 - - 0.50 2759 Brazil test OLKR12 404.41 45 21.70 41.53 - - 0.52 2728 Brazil test OLKR12 573.13 45 19.57 41.46 - - 0.47 2775 Brazil test OLKR12 400.37 70 19.27 41.54 - - 0.46 2727 Brazil test OLKR12 619.12 70 19.40 41.20 - - 0.47 2728 Brazil test OLKR12 619.26 70 19.57 41.19 - - 0.48 2719 Brazil test OLKR12 619.85 78 21.09 41.30 - - 0.51 2807 Brazil test OLKR12 618.31 80 21.96 41.32 - - 0.53 2713

24

3.2 Specimen handling procedure During the development and specification of laboratory tests, a procedure for specimen handling was introduced (Hakala 1996). This procedure was improved based on experience with the testing of Olkiluoto mica gneiss, Romuvaara tonalite gneiss, Kivetty granite, Kivetty porphyritic granodiorite and Hästholmen pyterlite (Hakala & Heikkilä 1997a, Heikkilä & Hakala 1998a, Heikkilä & Hakala 1998b, Eloranta & Hakala 1998 and Eloranta & Hakala 1999). In the following text, descriptions of the different handling stages are given. At each handling stage, special care was taken to report all occurrences deviating from the normal procedure. In the core sample selection phase at Geological Survey of Finland's Loppi storage, the bottom and top end of each core sample were marked. Before specimen preparation the core samples were stored in sample boxes. Specimen preparation begins with measurement of the length of each continuous core sample part. Then, the specimen identifiers and the cut lines of each test specimen were marked on the cores. The identifier naming system consisted of the borehole name ‘OLKR12-’ and the upper depth of the specimen within one centimeter accuracy, e.g. ‘543.21’. The cut levels and the downward arrows were also marked on the remaining parts of the cores. A file form was opened for each specimen (Appendix 1). The specimens were cut from the core samples with a 350 mm diameter diamond saw. During the sawing, the core was held by hand and the blade pressure controlled manually. After sawing, the specimen the ends were made flat with a grinding machine to fulfill the ISRM (1986) recommended procedure. The prepared specimens were then photographed and stored in a sample box in warm storage room conditions with a mean temperature of 22°C and 30 - 40% air humidity until testing. Normally testing is done with fully saturated specimens but here normal room conditions were used because of strain gauge gluing. On a day before testing, the length, diameter, mass, perpendicularity of specimen ends and the straightness of sample sides were measured and the strain gauge rosettes were glued. All length dimensions were measured to within 0.01 mm accuracy and the mass to within 0.1 grams accuracy. The perpendicularity of the specimen ends and the straightness of the sample sides were taken as the maximum difference. A technique for specifying the specimen side wall flatness was drafted, because no generally accepted defining method existed. Prior to loading, information concerning the test type, test control file, resulting data file, test control method and loading rate were recorded. Also, the gap between the circumferential extensometer jaws was recorded as an essential value in calculating the radial strain from the measured circumferential displacement. The test instrumentation was reported to the MTS testing system diary. The tests were conducted according to the

25

suggested test procedures introduced later on in Sections 4.2 to 4.4. All the test results were stored in digital form, and only the maximum axial load and confining pressure were recorded in the specimen file form. After each test, the observed failure surfaces were marked on the specimen and photographed. The tested specimens are stored in sample boxes at LRE / HUT until they were finally returned to Posiva.

27

4 TEST CONFIGURATIONS AND PROCEDURES

4.1 Testing devices

4.1.1 MTS 815 Rock mechanics testing system For all tests, an MTS 815 Rock Mechanics Testing System, a computer-controlled servo-hydraulic compression machine, was used. The system consists of a load cell, extensometers for strain measurements, load frame, hydraulic power supply, test controller, test processor and PC micro-computer (Figure 4-1).

Digital and Temperature Controller

Load UnitControl

Separateservovalves andpress. accum.

Temperature Chamber-60 ... +200 C

Load Frame-1.3 ... 2.6 MN

Pore Pressure0...80 MPa

Confining Pressure0...80 MPa

MTS815

PC Workstation &TestStar Software

User InterfaceTest ExecutionDevelopmentEnvironmentData StorageData AnalysisNetworking

Specimen LoadingDisplayHydraulic Controls

Triaxial testing:250 kN and 2500 kN load cellscircumferential extensometeraxial extensometers (2)

Uniaxial testing250 kN and 500 kN load cellscircumferential extensometeraxial aver. extensometers (3)

DDC Servo ControlData AcquisitionFunction GenerationLimit Checking

Digital I/OSignal ConditioningValve DriverReadout

Instrumentation

Digital Closed Loop Control

Figure 4-1. MTS 815 Rock Mechanics Testing System.

28

4.1.2 Strain gage measuring system Deformations were measured with strain gages and extensometers. A PC-based multi-channel electronic measurement system was used for data acquisition (Figure 4-2). The carrier-frequency measuring amplifier and analog to the digital converter unit, Spider 8, is manufactured by Hottinger Baldwin Messtechnik GmbH. The strain gage measurement system is completely independent and, during the tests, the axial force from the MTS testing system was recorded as an external channel to synchronize the data with the stress-strain data. Triaxial Kyowa KFG-10-120-D17-11L1M2S 2-wire cable strain gages and Kyowa KFG-10-120-D17-11L1M3S 3-wire cable strain gages were used for the strain measurements (Figure 4-3). The Kyowa strain gage model number coding system is shown in Figure 4-4. The adhesive used was Kyowa CC-33A.

Figure 4-2. The strain gage measurement system.

Figure 4-3. Triaxial Kyowa KFG-10-120-D17-11L1M3S 3-wire cable strain gage.

29

Figure 4-4. The Kyowa strain gage model number coding system.

4.1.3 Acoustic emission (AE) measuring system In addition to the stress-strain measurements, AE measurements gave direct information on micro cracking. The two channel acoustic emission (AE) measurement system was used for the uniaxial tests (Figures 4-5). It is manufactured by Physical Acoustics Corporation (PAC). The system included two piezoelectric transducers (PAC-R15), two 20-1200 kHz bandwidth preamplifiers (PAC-1220A, an AE analyzator (PAC AEDSP 32/16) and a data control and collection unit (Physical Acoustics Corporation 1995). The AE measurement system is a completely independent system. During the tests, the axial force from the MTS test system was recorded as an external channel to synchronize the AE data with the stress-strain data. In the system used, the data acquisition could be controlled by the following factors: a) the pre-amplification level can be changed between 40 dB or 60 dB; b) in the AE analyzer, the signal amplification level can be changed over a range of 0 to 20 dB; c) after filtering and amplification of the signal a 0 to 10 volts threshold for an event and count detection is set (Figure 4-6.) and d) finally, the selected death time assigns the time span for one event, i.e., the first hit from any channel above the threshold value starts the count collection time period for one event. After the death time, all sensors are ready to detect the next event. In all tests, the preamplification was 40 dB; no analyser amplification was used; the threshold was 0.1 V; and the dead time was 0.5 ms.

30

AE sourcein specimen

Transduser onspecimen surfacePAC-R15

Preamplifier

AE - analysator

Control, Aquistision andData analysis

PACAEDSP 32/16 PAC-1220A

- PC Win workstation- PAC Mistras Software

Figure 4-5. Two channel acoustic emission (AE) measurement system. Based on selected acquisition control equipment and values, the system records the following: timing between channels, duration, sum of counts, energy, maximum amplitude, rise time and three external channel values for each event (Figure 4-6). During the tests, the axial force from the MTS test system was recorded as an external channel to synchronize the AE data with the stress-strain data. Prior to loading, the transducer connection and the AE system were tested with an AE reference source, produced by breaking a 0.5 mm diameter, 3 mm long, 2H pencil lead using a Teflon guide ring. For an acceptable configuration, approximately 90 dB maximum amplitude is required. This test is generally known as the ‘pen test’.

31

Relative Energy( MARSE ), ( E )

Threshold

Rise Time, R

Duration, D

Amplitude, A

Acoustic Emission EventSix Counts

Time ( s )

Amplitude ( V )

Figure 4-6. Parameters describing an AE event (from Pollock 1989)

4.2 Uniaxial compression tests Uniaxial compression tests, with specimens of 42 mm and 52 mm diameter, were used to study the stress-strain behavior of Olkiluoto mica-gneiss. Two direct contact axial extensometers were used to measure axial strain (Figure 4-7) over a 50 mm gage length. The radial strain was measured with a single circumferential extensometer connected to the roller chain assembly wrapped around the specimen. All extensometers were held around the specimen by contact force produced by mounting springs. The actuator movement was also measured. At the specimen ends, non-lubricated steel end caps of the same diameter as the specimens were used. In order to assure uniform load distribution, the axial load was applied through one spherical seat.

32

Axial Extensometers

Specimen

Lower End Cap

Upper End Cap

Spherical Seat

Roller ChainAssembly

M T SMODEL632.11

CircumferentialExtensometer

Figure 4-7. Extensometer configurations in the uniaxial test. In addition to the extensometer measurements, strains were also measured by strain gages. Each specimen was equiped with four triaxial strain gage rosettes. The direction of the rosettes was chosen such that one gage measured axial strain, the second gage radial strain, and the third gage measured strain in 45º direction. Two rosettes on opposite sites of specimen were on the line of dip direction of the foliation (rosettes A and C in Figure 4-8) and the other two were perpendicular . All strain gauges were at the same distance from the end of the specimen. The acoustic emission (AE) sensor was located on the upper part of the sample and fixed on the specimen with a rubber band. An aluminium spacer was used to fit the transducer with a round specimen surface (Figure 4-9). Silicone grease couplant (Hoch-Vakuumfett / Wacker -Chemie GmbH, München) was used to improve the wave transfer between the rock surface and the transducer. A specimen ready for testing with all the instrumentation is shown in Figure 4-10.

33

AB

C

D

axialinclined

circumferential

dip offoliation

Figure 4-8. Strain gage configuration in the uniaxial test as related to the dip direction of foliation in the rock specimen.

Specimen

AE Sensor

Spacer

Rubber Band

Couplant

Figure 4-9. Horizontal cross-section of AE sensor installation.

34

Figure 4-10. Extensometers, strain gages and AE-sensors installed on the specimen. The uniaxial compression tests were conducted under radial strain rate control, corresponding to an elastic axial loading rate of 0.75 MPa/s. The ISRM (1986) suggestion for the uniaxial loading rate is 0.5 - 1.0 MPa/s. The uniaxial compression tests with a 0.75 MPa/s loading rate were conducted according to Table 4-1. The specimen is driven to contact under programmed control to obtain exact zero stress extensometer readings. One loading loop in the elastic region was completed to ensure a well-settled sample before loading it to failure. In both of these loading steps, axial load control was used first to overcome the radial extensometer hysteresis and, after that, the control was changed to radial strain to ensure a controlled test condition in the post failure phase.

35

Table 4-1. Procedure for uniaxial compression test.

1 Drive specimen manually near to contact - no axial force allowed.

2 Reset readings - reset the readings of axial and radial extensometer, actuator

displacement and axial force.

3 Start programmed test control

4 Drive specimen to force contact - move actuator up 0.2 mm/min until axial force is 1.0 kN,

the maximum actuator movement allowed is 3 mm.

5 Axial loading loop to settle specimen 5a Increase axial load so that loading rate is 0.75 MPa/s until

radial strain is -0.01% or axial stress is 35 MPa. 5b Decrease axial load so that loading rate is 0.75 MPa/s until axial

force is 1.0 kN.

6 Loading to ‘failure’ 6a Increase axial load so that the loading rate is 0.75 MPa/s until

radial strain is -0.01% or axial stress is 35 MPa. 6b Change to radial strain rate control. 6c Increase radial strain corresponding to the elastic loading rate of

0.75 MPa/s until the end of the radial extensometer range.

7 Unloading - Decrease axial load to zero with 50 kN/min loading rate.

4.3 Indirect Brazilian tensile tests In the indirect Brazil tensile test, only the applied load and actuator movement are measured. The compressive load is applied in a direction normal to the specimen circumferential surface inducing a lateral tension to the specimen (Figure 4-11). The load was applied through two 3.5 mm wide flat steel jaws. To extend the contact area from the theoretical point contact, a 0.15 mm thick paper tape was used around the specimen. This loading configuration is not, however, according to the ISRM (1986) suggestion – in which the specimen is loaded between two concave steel plates having a

36

surface radius 1.5 times the specimen radius. The reason for the modified system used was because it is the standard practice of the test laboratory. Two strain gage rosettes were mounted on all the Brazilian test specimen. The orientation of the rosettes was chosen such that one gage measured axial strain in the loading direction and the other measured the strain perpendicular to the loading; then, the third gage measured strain in the 45º direction (Figure 4-12). In the test procedure used, the specimen was first driven slowly to contact (Table 4-2). After that, the tensile test was conducted with constant compressive rate of the actuator movement.

Jaws with 3.5 mmContact Width

Specimen

Lower End Cap

Tape AroundSpecimen

Upper End Cap

Spherical Seat

Figure 4-11. Indirect Brazilian tensile test configuration.

37

ψ

ϕ

εε

ε

Figure 4-12. Strain gage configuration in the Brazilian test. Table 4-2. Procedure for the indirect Brazilian tensile test.

1 Drive specimen manually near to contact - no axial force allowed.

2 Reset readings - reset readings of the actuator displacement and axial force.

3 Start programmed test control

4 Drive specimen to force contact - move actuator up 0.2 mm/min until the axial force is 1.0 kN,

the maximum actuator movement allowed is 3 mm.

5 Loading to tensile failure - Move actuator up with a speed corresponding to 200 Pa/s elastic

loading rate, maximum actuator movement is restricted to 4 mm.

38

4.4 Quality control To assure that all test phases were undertaken on each specimen in the planned order, and to make it possible to re-analyze possible errors and deviations in the results, all the preparation and test phases of each specimen were recorded on a test information form (Appendix 1). MTS test system is calibrated only after updates possibly affecting to test results. Last time was in the end of year 2002 when the whole system was remounted after renoval of the laboratory. Between the calibrations the extensometer readings were regularly checked using a 56 mm aluminum calibration specimen. The reference values for the aluminium specimen were obtained immediately after the extensometer calibration. This calibration checking was completed after every ten specimens – or at the beginning of a new test series. The monitored values are Young’s modulus and Poisson’s ratio. Both values were determined as a secant from the range of 0.01% radial strain to 150 MPa axial stress. In this study, single axial extensometer was used instead of three averaging axial extensometers which were used in Posiva Oy’s previous rock mechanics tests. The calibration values for the single axial extensometers were a little higher than the averaged values of the three axial extensometers but there was no trend or high scattering to indicate any malfunctioning (Figure 4-13 and Figure 4-14). Until the year 1999, the mean value for the Young’s modulus of the aluminum calibration specimen was 75 GPa and the 95% confidence limits for standard deviation were 73 GPa to 77 GPa (Eloranta & Hakala 1999); the associated values for Poisson’s ratio were 0.32 and 0.30 to 0.33. Compared to these confidence limits, occasional peaks in the Young’s moduli values exist, but Poisson’s ratio was more unstable. After mid 2002, the values have been more stable but still there are peaks in the Poisson’s ratio value. No clear reason for these observed peaks exists, but one probable reason is related to how accurately the axial and circumferential extensometers can be mounted on the specimen surface i.e, so that they are accurately parallel to and perpendicular to the specimen axis.

39

69.00

70.00

71.00

72.00

73.00

74.00

75.00

76.00

77.00

78.00

79.00

80.00

28.10.1995 11.3.1997 24.7.1998 6.12.1999 19.4.2001 1.9.2002 14.1.2004 28.5.2005

Date

Youn

g's

mod

ulus

(GPa

)Three averaging axialextensomters

Single axialextensometer

Figure 4-13. Young's modulus for the aluminum calibration specimen no. 2.

0.29

0.3

0.31

0.32

0.33

0.34

0.35

0.36

0.37

0.38

28.10.1995 11.3.1997 24.7.1998 6.12.1999 19.4.2001 1.9.2002 14.1.2004 28.5.2005

Date

Pois

son'

s ra

tio

Three averaging axialextensomters

Single axialextensometer

Figure 4-14. Poisson's ratio of aluminum calibration specimen no. 2 (note that the radial extensometer was changed in mid 1997).

41

5 TEST RESULTS

5.1 Stress-strain behaviour Detailed stress-strain curves from strain gage measurements and MTS-extensometers measurements are presented in Appendix 3. Mean apparent stress-strain curves with different anisotropy angles to the loading axis are shown in Figure 5-1.

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( mm/mm )


Figure 5-1. Stress-strain curves with different anisotropy angle.

42

5.2 Elastic parameters Transverse isotropic parameters Applying Amadei’s solution (Chapter 2.2) for the strain gauge responses of the 19 specimens showed a mean anisotropy factor of 1.4 for Young’s modulus:

E = 79 GPa E' = 56 GPa ν = 0.17 ν' = 0.21 G' = 24 GPa E / E' = 1.40

The empirical Saint Venant’s relation for G′ according to Equation 1-4 gives value of 33 GPa – which is 36% higher than the measured value. In axial loading, the apparent Young’s modulus Ey and Poisson’s ratios νyx νyz for different angles of θ can be calculated from Equations 2-10. The mean error for the measured apparent Young’s modulus values and anisotropic solution is 7% and the correlation coefficient is 0.73 (Figure 5-2). For the apparent Poisson’s ratio values νyx and νyz, the corresponding values are 18% / 0.08 and 10% / 0.09 (Figures 5-3 and 5-4). The anisotropic solution was applied to different loading stages for the first 10 specimens, resulting in moderate differences compared to the final values based on 19 specimens (Table 5-1): Table 5-1. Results from the application of the transversely isotropic solution to different loading stages.

Loading stage / Load Parameter 1st, loading 1st unloading 2nd loading 2nd loading 2nd loading

23 % of σp 23 % of σp 33 % of σp 50 % of σp 70 % of σp E ( GPa ) 76 73 80 81 81 E' ( GPa ) 46 43 51 51 51 ν (-) 0.15 0.15 0.17 0.17 0.18 ν' (-) 0.17 0.17 0.18 0.20 0.22 G' ( GPa ) 24 22 25 24 23 E/E' ( % ) 164 170 157 158 158 G′SV ( GPa ) 29 27 31 31 31 (G′SV-G′)/G′ 21 22 26 31 37

43

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100 ( GPa )

( G

Pa )

Ey=40GPaEy=60GPaEy=80GPaLS-Fit for Transverse isotropyMeasured

15°

30°

45°

60°

75°

Figure 5-2. Polar plot of mean apparent Young’s modulus. Measured values and results from transverse isotropic solution.

0.0

0.1

0.2

0.3

0.0 0.1 0.2 0.3

ny_xy=0.10ny_xy=0.20ny_xy=0.30LS-Fit for Transverse isotropyMeasured

15°

30°

45°

60°

75°

Figure 5-3. Polar plot of mean apparent Poisson’s ratio νyx. Measured values and results from transverse isotropic solution.

44

0.0

0.1

0.2

0.3

0.0 0.1 0.2 0.3

ny_yz=0.10ny_yz=0.20ny_yz=0.30LS-Fit for Transverse isotropyMeasured

15°

30°

45°

60°

75°

Figure 5-4. Polar plot of mean apparent Poisson’s ratio νyz. Measured values and results from transverse isotropic solution. Apparent Young’s modulus The measured apparent Young’s modulus varies from 37 GPa to 95 GPa, depending on the anisotropy angle (Figure 5-5). Between anisotropy angles 10-45º, there is no major difference in the values of Young's modulus. With larger anisotropy angles, 70-80º, the Young's modulus is higher. The values measured by the MTS axial extensometers were generally slightly higher than the strain gauge values. The results from previous laboratory tests (Hakala & Heikkilä 1997a and 1997b), representing mainly foliation dip angles between 30° to 60° and all degrees of foliation, did not show correlation with the dip of foliation. This observation and the previously defined mean values and deviations consistent with the new results (Figure 5-6).

45

0

10

20

30

40

50

60

70

80

90

100

0 10 15 20 22 25 27 27 27 42 42 45 45 45 70 70 70 78 80

Strain Gages

MTS-extensometer

Young's Modulus (GPa)

Anisotropy angle (degrees)

Figure 5-5. Apparent Young's modulus for each test specimen, estimated from strain gauges and MTS axial extensometer readings.

66

57

6460

69

6257

4351

43

53

43

57

50

43

24

82

727677

80

7371

61

0

10

20

30

40

50

60

70

80

90

100

DT 1A-Slw 1A-Nrm 3A-0.5 3A-1 3A-3 3A-5 3A-15

Test Configuration

Young's Modulus ( GPa )

Olkiluoto Mica Gneiss95% Confidence for Stardard Deviationand Average, n = 110

n=20

n=15

n=25

n=8

n=8n=18

n=8

n=8

Figure 5-6. Young's modulus from different test configurations (specimens from borehole OL-KR10, Hakala & Heikkilä 1997a).

46

Apparent Poisson's ratio Detailed stress-strain curves from strain gage measurements and MTS-extensometer measurements are presented in Appendix 3. The measured Poisson's ratios vary from 0.13 to 0.37. A distinct trend between the anisotropy angle and the Poisson's ratio value cannot be observed (Figure 5-7). Values calculated from the axial and tangential strain gauge readings are higher than the values based on the MTS axial and circumferential extensometers. No clear reasons for this were found. The results from previous laboratory tests (Hakala & Heikkilä 1997a and 1997b), representing mainly foliation dip angles between 30° to 60° and all degrees of foliation, did not show correlation with the foliation dip value. This observation, together with the previously defined mean values and deviations, are consistent with the new results (Figure 5-8).

0.0

0.1

0.2

0.3

0.4

0.5

0 10 15 20 22 25 27 27 27 42 42 45 45 45 70 70 70 78 80

Strain Gages

MTS-extensometer

Poisson's ratio ( )

Anisotropy angle (degrees)

Figure 5-7. Apparent Poisson’s ratio for each test specimen defined from readings of strain gauges or MTS extensometers.

47

0.19

0.220.200.20

0.19

0.280.28

0.06

0.02

0.23 0.24

0.15

0.12

0.160.14 0.14

0.23 0.23

0.30

0.32 0.32

0.23

0.29

0.09

0.0

0.1

0.2

0.3

0.4

0.5

DT 1A-Slw 1A-Nrm 3A-0.5 3A-1 3A-3 3A-5 3A-15

Test Configuration

Poisson's Ratio ( mm/mm )


n=17

n=15 n=25

n=8n=8n=18

n=7

n=8

Figure 5-8. Poisson's ratio from different test configurations (specimens from borehole OL-KR10, Hakala & Heikkilä 1997a).

48

5.3 Strength parameters Crack initiation The crack initiation stress (σci) was evaluated from the MTS-extensometer and AE-data. A distinct trend between the anisotropy angle and the crack initiation stress level cannot be observed (Figure 5-9 and Figure 5-10). From AE-data two crack initiation stress values were defined; the first value -σci,1 value is the stress level where the low energy AE-emission starts after the emission induced by the settling of the specimen; the second value σci,2 is the stress level where the cumulative number of AE events increases with applied load or middle energy level emission start (Figure 5-11 and Appendix 1). In many cases, the definition of the crack initiation value as estimated from the measured acoustic emission was not clear, or it overlapped the settling of the specimen ends. Generally, the upper value of AE_s_ci2 correlates better with the crack initiation value defined from extensometer readings, but the lower values indicate that microcracking has started in most of the cases at a lower loading level. The extensometers-measured σci values (40…83 MPa, mean 55 MPa) correspond quite well to the σci values from previous laboratory tests (Hakala & Heikkilä 1997a and 1997b) (Figure 5-12).

0

25

50

75

100

125

150

175

0 10 15 20 22 25 27 27 27 42 42 45 45 45 70 70 70 78 80

MTS_s_ci

AE_s_ci1

AE_s_ci2

Axial stress (MPa)

Anisotropy angle ( degrees ) Figure 5-9. Crack initiation stress level for each specimen defined from extensometer readings and acoustic emission measurements.

49

0

25

50

75

100

125

150

175

0 10 20 30 40 50 60 70 80 90

Anisotropy angle ( degrees )

Cra

ck in

itiat

ion

stre

ss (

MPa

)Effect of Anisotropy on Crack Initiation Stress- Mean, standard deviation and number of tests values for three anisotropy angle regions- Crack initiation stress is 41% - 49% of peak strength

55 MPa4.4 MPan=8

56 MPa15.8 MPan=5

55 MPa8.9 MPan=5

Figure 5-10. Crack initiation stress level (from MTS readings) versus anisotropy angle.

0

100

200

300

400

500

0 20 40 60 80 100 120


1

10

100

1000

10000

100000

6 ( 31% )

11 ( 64% )

33 ( 90% )

59 ( 95% )

2287 ( 100% )

All ( log )

Cumulative number of AE events ( pcs )

Upper limit for energy and percentage of events below energy level

Critical stress levels:

microcracking initiates: 39 - 47 MPa

high energy microcracking initiates: 69 MPa

unstable microcracking: 87 - 96 MPa

peak strength: 102 MPa

OLKR14 - 333.11mica gneissdip of foliation 0°

Figure 5-11. Example of measured AE events at different stress/energy levels.

50

403236

2632

3829

60 6170 70 72 67

115

0

50

100

150

200

250

1A-Slw 1A-Nrm 3A-0.5 3A-1 3A-3 3A-5 3A-15

Test Configuration

Crack Initiation ( MPa )


n=15n=23

n=8n=8 n=18 n=8

n=8

45 50 4851

78

4954

Figure 5-12. Crack initiation stress level for different test configurations (specimens from borehole OL-KR10, Hakala & Heikkilä 1997a).

51

Crack damage The crack damage stress (σcd)was evaluated from MTS-extensometer data and from AE-data (Figure 5-13). From AE-data two crack damage values were defined. The first value σcd,1 is for the onset of high energy level emission and the second value σcd,2 is for exponential increase of emission (Figures 2-8, 5-13 and Appendix 1). The interpretation of crack damage from acoustic emission results gives the same trend as the interpretation from measured strains. In the majority of cases, high energy emission starts before strain-based crack damage. On the other hand, the emission rate changes to exponential at the same or higher stress level than the strain-based crack damage value. There seems to be a slight link between crack damage and anisotropy angle (Figure 5-14) which corresponds to the single plane of weakness theory about strength and anisotropy angle, but deviations in the results are quite high. The new crack damage values are higher than values from previousllaboratory tests (Hakala & Heikkilä 1997a and 1997b). One reason for this might be the saturation of test specimens: in the current work, the specimens were stored at normal room conditions; whereas, earlier, wet specimens were used (Figure 5-15).

0

25

50

75

100

125

150

175

0 10 15 20 22 25 27 27 27 42 42 45 45 45 70 70 70 78 80

MTS_s_cd

AE_s_cd1

AE_s_cd2

Axial stress (MPa)


Figure 5-13. The crack damage stress level for each specimen established from extensometer readings and acoustic emission measurements.

52

0

25

50

75

100

125

150

175

0 10 20 30 40 50 60 70 80 90


Cra

ck d

amag

e st

ress

, ( M

Pa )

Effect of Anisotropy on Crack Damage Stress- Mean, standard deviation and number of tests values for three anisotropy angle regions- Crack damage stress is 91% - 97% of Peak strength

125 MPa18.6 MPan=8

110 MPa15.6 MPan=5

129 MPa26.5 MPan=5

Figure 5-14. Crack damage stress level (MTS) versus anisotropy angle.

95

48

67

5254

68

49

104116 110

103

136124

171

0

50

100

150

200

250

1A-Slw 1A-Nrm 3A-0.5 3A-1 3A-3 3A-5 3A-15

Test Configuration

Crack Damage ( MPa )


n=13

n=23

n=7n=7n=18

n=7

n=8

76

92

7782

132

86

101

Figure 5-15. Crack damage stress level from different test configurations (specimens from borehole OL-KR10, from Hakala & Heikkilä 1997).

53

Peak strength Like crack damage values, there seems to be some trend between peak strength and anisotropy angle (Figure 5-16 and 5-17) which corresponds to strength versus anisotropy angle, as interpreted via the single plane of weakness theory. The mean peak strength is higher than the values measured in previous laboratory tests (Hakala & Heikkilä 1997a and 1997b) (Figure 5-18), which may be a result of the test room saturated samples used; in the previous tests wet samples were used.

0

25

50

75

100

125

150

175

0 10 15 20 22 25 27 27 27 42 42 45 45 45 70 70 70 78 80

Axial stress ( MPa )


Figure 5-16. Peak strength of each specimen.

54

0

25

50

75

100

125

150

175

0 10 20 30 40 50 60 70 80 90


Peak

str

engt

h (

MPa

)

Effect of Anisotropy on Peak Strength- Mean, standard deviation and number of tests values for three anisotropy angle regions

137 MPa16.1 MPan=8

113 MPa18.3 MPan=5

132 MPa29.8 MPan=5

Figure 5-17. Peak strength versus anisotropy angle.

93

54

71

5668

76

59

132138

115124

139 139

188

0

50

100

150

200

250

1A-Slw 1A-Nrm 3A-0.5 3A-1 3A-3 3A-5 3A-15

Test Configuration

Peak Stength ( MPa )


n=13

n=23

n=7n=7 n=17

n=7

n=8

95107

9092

140

96105

Figure 5-18. Peak strength from different test configurations (specimens from borehole OL-KR10, from Hakala & Heikkilä 1997).

55

Tensile strength The tensile strength decrease versus anisotropy angle is illustrated in Figure 5-19. The dispersion is also quite high also in these measurements. The mean tensile strength is higher than the values measured in previous laboratory tests (Hakala & Heikkilä 1997a and 1997b) (see Figure 5-20), which may be a result of the test room saturated samples used; in previous tests wet samples were used.

0.0

5.0

10.0

15.0

20.0

25.0

0 10 20 30 40 50 60 70 80 90


Tens

ile s

tren

gth

( M

Pa )

Effect of Anisotropy on Indirect Tensile strength- Mean, standard deviation and number of tests values for three anisotropy angle regions

16.5 MPa2.1 MPan=8

14.1 MPa2.3 MPan=5

12.5 MPa2.4 MPan=5

Figure 5-19. Tensile strength versus anisotropy angle.

56

-6.4-5.4

-2.6

-1.0

-3.9

-9.0-9.8

-13.9

-25

-20

-15

-10

-5

0

DT-Sci DT-Scd DT-Peak Brazil-Peak

Test Configuration

Critical Tensile Stress ( MPa )


n=4

n=4

n=19

n=18

-2.5

-5.8

-10.1

-7.9

Figure 5-20. Critical Tensile stresses from direct tensile tests and indirect Brazil tensile tests (specimens from borehole OL-KR10, from Hakala & Heikkilä 1997a).

57

6 CONCLUSIONS, DISCUSSION AND RECOMMENDATIONS

The testing, estimation and interpretation of the anisotropic elastic deformation parameters for Olkiluoto mica gneiss were successful and highlighted a transverse anisotropy of 1.4 in the Young’s modulus parallel and perpendicular to the foliation. This ratio is high enough to produce significant errors in the interpretation of the magnitudes and orientations of in situ principal stresses if the anisotropy is not taken into account. This means that an anisotropic solution for stresses should definitely be used. The trends of the results as a function of the anisotropy angle were not always completely clear because there were only few specimens with a foliation dip of less than 15° or above 80° which are important in studying the trends and also the angles between 45° to 60° were missing. Also, it was assumed that the ‘visually seen’ orientation of the foliation was also the actual mechanical transverse isotropy plane. One possible method to check this would be to compare the responses of opposing strain gauges which should be close to each other (Figure 4-8). Another possibility would be to use radial P-wave measurements to obtain the orientation for the deformation anisotropy plane. Compared to previous test results for the Olkiluoto mica gneiss, the apparent Young’s modulus and apparent Poisson’s ratio are similar but the critical stress values are higher. The crack initiation stress is about 10% higher but there is no clear effect of the anisotropy. The crack damage and peak stresses are 6-40 higher, having lowest values at medium angles of anisotropy. The indirect tensile strength was 25-65% higher, having the lowest tensile strength in a direction perpendicular to the plane of anisotropy. One major reason for higher critical stress values is the test room condition for the samples – compared to the saturated samples used in earlier tests. Another reason could be the different sample locations. Theoretically, assuming the single plane of weakness theory is applicable to the failure of a foliated rock, the lowest strength values should be associated with foliation orientations of 45° +(φ/2), where φ is the friction angle (Figure 6-1). Although the crack damage stress, peak strength and tensile strength showed some trend with anisotropy, the dispersion of results was high. In any case, the observed strength behaviour can be explained by assuming that crack initiation is dominated by favourably oriented weakest mineral contacts; whereas crack damage and peak strength (i.e. coalescence of micro fractures) is dominated by the orientation of the foliation (Figures 6-1 and 6-2).

58

Figure 6-1. Observed effect of anisotropy on critical stress state values (modified from Hudson & Harrison 1997).

a. b. Figure 6-2. (a) Initiation of microcracking dominated by favourably orientated weak grain contacts and (b) coalescence of microcracks dominated by foliation. In the context of the motivation for this specific research and because of the regional orientation of foliation and sub-vertical boreholes used in the Olkiluoto area in Finland, it is difficult to find specimens in close proximity which have suitable angles of foliation. Therefore, for this project, it is recommended to continue the testing and interpretations of anisotropy with orientated samples taken in the ONKALO access ramp close to the first in situ stress measurement location – in order to enable the use of

59

the correct transverse isotropic interpretation method for in situ stress measurements and to increase the quality of test information. For other projects involving the estimation of in situ rock stress in foliated rocks, or in other rocks exhibiting transverse anisotropy, we recommend that the transverse isotropy solution is used. Consideration should also be given to the testing issues – as highlighted in this paper. An adequate estimate of the elastic parameters of the rock is necessary and this involves the additional sampling and testing considerations for the case of a foliated or other rock type exhibiting transverse isotropy.

61

REFERENCES

Amadei, B., 1983. Lecture Notes in Engineering - Rock Anisotropy and Theory of Stress Measurements. Edited by C. A. Brebbia and S.A. Orszag. Springer-Verlag, Berlin. pp 233 -241. Amadei, B., Savage, W. Z. & Swolfs, H. S., 1987. Gravitational stresses in anisotropic rock masses. Znt. J. Rock Mech. Min. Sci. &Geomech. Abstr. 24, 5-14. Amadei, B., 1996. Importance of Anisotropy When Estimating and Measuring In Situ Stress in Rock. Int. J. Rock Mech. Min. Sci. & Geomech. Abstr. Vol 33, No. 3, pp. 293-325. Chen, C., Pan, E. & Amadei, B., 1998. Determination of Deformability and Tensile Strength of Anisotropic Rock Using Brazian Test. Int. J. Rock Mech. Min. Sci. & Geomech. Abstr. Vol 35, No. 1, pp. 43-61. Christianson, R. & Hudson, J.A., 2002. Quality control of in situ rock stress measurements. Sweden: Lenssons from the Äsoö Hard Rock Laboratory. Eloranta, P. & Hakala, M., 1998. Work Report - Laboratory testing of Kivetty porphyritic granodiorite in borehole RO-KR10. Posiva Working Report 98-06e. Posiva Oy, Helsinki. Eloranta, P. & Hakala, M., 1999. Work Report - Laboratory testing of Hästholmen pyrterlite in borehole HH-KR6. Posiva Working Report 99-26. Posiva Oy, Helsinki. Hakala, M., 2003. Quality control for overcoring stress measurement data. POSIVA 2005-13. Posiva Oy, Olkiluoto. (to be published) Hakala, M., 1996. Stress-Strain Behaviour of Crystalline Rock - Literature Study and Development of Test Program . Work Report TEKA-96-08e. Posiva Oy, Helsinki. Hakala, M. & Heikkilä, E., 1997a. Laboratory testing of Olkiluoto mica gneiss in borehole OL-KR10. Work report POSIVA-97-07e. Hakala, M. & Heikkilä, E., 1997b. Summary Report - Development of Laboratory Tests and Stress-Strain Behaviour of Olkiluoto Mica Gneiss. Posiva Report 97-04. Posiva Oy, Helsinki.

62

Heikkilä, E. & Hakala, M., 1998a. Work Report - Laboratory testing of Romuvaara tonalite gneiss in borehole RO-KR10. Posiva Working Report 98-06e. Posiva Oy, Helsinki. Heikkilä, E. & Hakala, M., 1998b. Work Report - Laboratory testing of Kivetty granite in borehole KI-KR10. Posiva Working Report 98-21e. Posiva Oy, Helsinki. Hudson, J. A. & Harrison, J. P., 1997. Engineering Rock Mechanics – An Introduction to the Principles. Pergamon. ISRM, 1986. Rock Characterization Testing and Monitoring, ISRM Suggested Methods. Brown E. T., editor. Pergamon Press, Oxford. Martin, C. D., 1994. TVO/SKB/AECL Workshop on Rock Strength - Proceedings. Work Report TEKA-94-07. Teollisuuden Voima Oy, Helsinki. Martino, D. & Ribacchi, R., 1972. Osservazioni su alcuni metodi di masura delle carateristiche di occe o ammassi rocciosi, con particolare riferimento al problema dell’ anisotropa. L’Zndustria Mineraria, pp. 193-203. (In Italian). Niinimäki, R., 2000. Core drilling of deep borehole OL-KR12 at Olkiluoto in Eurajoki. Working Report 2000-28. Posiva Oy, Helsinki. Niinimäki, R., 2001. Core drilling of deep borehole OL-KR14 at Olkiluoto in Eurajoki 2001 (in Finnish with an English abstract). Working Report 2001-24. Posiva Oy, Helsinki. Physical Acoustics Corporation, 1995. Mistras-2001, AEDPS-32/16 User's Manual. Princenton. Pollock, A. A., 1989. Acoustic Emission Ispection. Authorized reprint from Metals Handbook Ninth Edition, Vol. 17, pp 278-294. ASM International. Saint-Venant, B., 1863. Sur la distribution des elastici& autour de chaque point d’un sohde ou dun milieu de contexture quelconque. J. de Mathematiques Pures et Appliquees 7-8, 353-430, 257-261. (In French). Vaittinen,T., Ahokas, H., Heikkinen, E., Hellä, P., Nummela, J., Saksa, P., Tammisto, E., Paulamäki, S., Paananen, M., Front, K., & Kärki, A., 2003. Bedrock Model of Olkiluoto Site, Version 2003/1. Working Report 2003-43. Posiva Oy, Olkiluoto.

63

Worotnicki, G., 1993. CSIRO triaxial stress measurement cell. In Comprehensive Rock Engineering (Edited by Hudson J. A.), Chap. 13,Vol. 3, pp. 329-394. Pergamon, Oxford.

65

APPENDICES

1 Test information form. 2 Photographs of uniaxial compression test specimen before testing and AE-

measurements results. 3 Stress-strain curves of uniaxial compression tests. 4 Photographs of tested specimen.

Appendix 1

66

Helsinki University of Technology Test information sheet for uniaxial compression test Page 1(2)Rock Engineering Form 03/PT

Order:

Specimen:1. Geological description

Person: Date:

Person: Date:Remarks:

2. SawingPerson: Date:

Remarks:

3. GrindingPerson: Date:

Remarks:

4. PhotographPerson: Date:

Filename for digital pictures: Remarks:

5. Storing in approximately 100% air humidityPerson: Date:

Weight before storing (g)

Start of storing: date time

End of storing: date time

Weight after storing (g)

End of drying on the table: date time

Remarks:

6. Physical propertiesPerson: Date:

Description

1 2 3Length (mm): Average:

1 2 3Diameter (mm):

4 5 6Average:

Weight (g):

Parallelism of ends (mm):

Straightness of sides:Maximum deviation (mm):

Remarks:

Appendix 1

67

Page 2(2)Specimen:

7. Bonding of strain gauges:Person: Date:

Adhesive:

Gage type:

Lot no. & Batch:

Gage factor:

Curing time before test (hh:min):

Angle ψ :

Remarks:

Gage names:

8. TestingPerson: Date:Test:

Template:

Data file:AE data file:

Strain gage data file:

Li mm Diam. on rubber mm

timeStart: Conf. pressure MPa

Failuretype Paused: Peak load kNContinued: Peak strength MPaEnd:

Remarks:

9. StoringPerson: Date:

Place:

Remarks:

ε

ε ε

ε

εε

ψ

Appendix 1

68

Helsinki University of Technology Test information sheet for Brazil tests Page 1(2)Rock Engineering Form 01/PT

Order:

Specimen:1. Geological description

Person: Date:

Person: Date:

Remarks:

2. SawingPerson: Date:

Remarks:

3. PhotographPerson: Date:

Filename for digital pictures:

Remarks:

4. Storing in approximately 100% air humidity:Person: Date:

Weight before storing (g)

Start of storing: date time

End of storing: date time

Weight after storing (g)

End of drying on the table: date time

Remarks:

5. Physical propertiesPerson: Date:

Description:

1 2 3Length (mm): Average:

1 2 3Diameter (mm):

4 5 6Average:

Weight (g):

Remarks:

Appendix 1

69

Page 2(2)Specimen:

6. Bonding of strain gagesPerson: Date:

Angle ψ :

Angle ϕ :

Adhesive:

Gage type:

Lot no. & Batch:

Gage factor:

Curing time before test (hh:min):

Remarks:

Gage names: (A) (B)

7. TestingPerson: Date:

Template:

Data file:

AE data file:

Strain gage data file:

timeStart: Peak load kN

Failure type: Stop: Peak strength MPa

Remarks:

8. StoringPerson: Date:

Place:

Remarks:

ψ

ϕ

εε

ε

Appendix 2 - page 1

70

0

100

200

300

400

500

0 20 40 60 80 100 120


1

10

100

1000

10000

100000

6 ( 31% )

11 ( 64% )

33 ( 90% )

59 ( 95% )

2287 ( 100% )

All ( log )


Upper limit for energy and

percentage of events below

energy level


microcracking initiates:

39 - 47 MPa

high energy microcracking initiates:

69 MPa

unstable microcracking:

87 - 96 MPa

peak strength:

102 MPa

OLKR14 - 333.11

mica gneiss

dip of foliation 0°

Appendix 2 - page 2

71

0

100

200

300

400

500

0 20 40 60 80 100 120 140


1

10

100

1000

10000

100000

6 ( 26% )

13 ( 61% )

60 ( 90% )

120 ( 95% )

3905 ( 100% )

All ( log )




energy level



36 - 44 MPa


67 MPa


94 - 122 MPa

peak strength:

126 MPa

OLKR14 - 334.14

mica gneiss


Appendix 2- page 372

0

800

1600

2400

3200

4000

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

6 ( 28% )

11 ( 59% )

36 ( 90% )

60 ( 95% )

5048 ( 100% )

All ( log )




energy level



73 MPa


102 MPa


153 MPa

peak strength:

155 MPa

OLKR12 - 556.79

mica gneiss


Appendix 2 - page 4

73

0

1000

2000

3000

4000

5000

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

7 ( 34% )

13 ( 61% )

49 ( 90% )

89 ( 95% )

4643 ( 100% )

All ( log )




energy level



12 - 52 MPa


12 MPa


105 - 165 MPa

peak strength:

165 MPa

OLKR12 - 535.14

mica gneiss


Appendix 2 - page 5

74

0

500

1000

1500

2000

2500

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

7 ( 31% )

14 ( 61% )

46 ( 90% )

75 ( 95% )

5051 ( 100% )

All ( log )




energy level



24 - 59 MPa


82 MPa


125 - 135 MPa

peak strength:

142 MPa

OLKR12 - 523.97

mica gneiss


Appendix 2 page 6

75

0

400

800

1200

1600

2000

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

6 ( 35% )

9 ( 60% )

24 ( 90% )

37 ( 95% )

865 ( 100% )

All ( log )




energy level



45 MPa


93 MPa


123 MPa

peak strength:

125 MPa

OLKR12 - 551.81

mica gneiss


Appendix 2 - page 7

76

0

200

400

600

800

1000

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

6 ( 29% )

11 ( 59% )

41 ( 90% )

72 ( 95% )

3453 ( 100% )

All ( log )




energy level



16 - 63 MPa


94 MPa


138 MPa

peak strength:

138 MPa

OLKR12 - 485.08

mica gneiss


Appendix 2 - page 8

77

0

100

200

300

400

500

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

6 ( 31% )

10 ( 60% )

32 ( 90% )

54 ( 95% )

3115 ( 100% )

All ( log )




energy level



38 MPa


75 MPa


122 MPa

peak strength:

123 MPa

OLKR12 - 485.31

mica gneiss


Appendix 2 - page 9

78

0

500

1000

1500

2000

2500

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

6 ( 28% )

11 ( 59% )

38 ( 90% )

64 ( 95% )

2329 ( 100% )

All ( log )




energy level



40 - 68 MPa


111 MPa


115 - 120 MPa

peak strength:

122 MPa

OLKR12 - 493.88

mica gneiss


Appendix 2 - page 10

79

0

400

800

1200

1600

2000

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

6 ( 34% )

10 ( 63% )

28 ( 90% )

43 ( 95% )

45825 ( 100% )

All ( log )




energy level



24 - 67 MPa


81 MPa


111 MPa

peak strength:

113 MPa

OLKR12 - 403.68

mica gneiss



80

0

1000

2000

3000

4000

5000

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

7 ( 30% )

15 ( 60% )

63 ( 90% )

117 ( 95% )

5203 ( 100% )

All ( log )




energy level



25 - 46 MPa


82 MPa


125 MPa

peak strength:

125 MPa

OLKR12 - 574.44

mica gneiss



81

0

100

200

300

400

500

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

7 ( 37% )

12 ( 60% )

42 ( 90% )

68 ( 95% )

799 ( 100% )

All ( log )




energy level



36 - 52 MPa


87 MPa


104 MPa

peak strength:

107 MPa

OLKR12 - 404.10

mica gneiss



82

0

100

200

300

400

500

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

6 ( 34% )

9 ( 60% )

23 ( 91% )

34 ( 95% )

826 ( 100% )

All ( log )




energy level



22 - 51 MPa


75 MPa


135 MPa

peak strength:

135 MPa

OLKR12 - 404.21

mica gneiss



83

0

100

200

300

400

500

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

6 ( 29% )

11 ( 60% )

41 ( 90% )

72 ( 95% )

3230 ( 100% )

All ( log )




energy level



30 MPa


77 MPa


86 MPa

peak strength:

87 MPa

OLKR12 - 573.02

mica gneiss



84

0

100

200

300

400

500

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

7 ( 31% )

16 ( 61% )

74 ( 90% )

149 ( 95% )

900 ( 100% )

All ( log )




energy level



60 MPa


99 MPa


99 MPa

peak strength:

99 MPa

OLKR12 - 400.26

mica gneiss



85

0

100

200

300

400

500

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

6 ( 30% )

11 ( 60% )

40 ( 90% )

75 ( 95% )

10951 ( 100% )

All ( log )




energy level



56 MPa


112 MPa


150 - 168 MPa

peak strength:

168 MPa

OLKR12 - 619.01

mica gneiss



86

0

200

400

600

800

1000

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

7 ( 31% )

14 ( 59% )

63 ( 90% )

119 ( 95% )

12666 ( 100% )

All ( log )




energy level



21 - 58 MPa


112 MPa


138 MPa

peak strength:

138 MPa

OLKR12 - 619.15

mica gneiss



87

0

100

200

300

400

500

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

6 ( 38% )

9 ( 63% )

24 ( 90% )

36 ( 95% )

498 ( 100% )

All ( log )




energy level



38 MPa


81 MPa


105 MPa

peak strength:

105 MPa

OLKR12 - 619.75

mica gneiss



88

0

100

200

300

400

500

0 25 50 75 100 125 150 175


1

10

100

1000

10000

100000

5 ( 25% )

8 ( 67% )

17 ( 90% )

26 ( 95% )

748 ( 100% )

All ( log )




energy level



53 MPa


112 MPa


152 MPa

peak strength:

152 MPa

OLKR12 - 618.48

mica gneiss


Appendix 3

89

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator


OLKR14 - 333.11 mica gneiss dip of foliation 0° crack initiation: 40 MPa crack damage: 87 MPa

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation

OLKR14 - 333.11mica gneiss


Appendix 3

90

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

91

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

92

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

93

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

94

0

25

50

75

100

125

150

175

-0.30 % -0.20 % -0.10 % 0.00 % 0.10 % 0.20 % 0.30 % 0.40 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

95

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator


OLKR12 - 485.08 mica gneiss dip of foliation 27° crack initiation: 59 ? MPa crack damage: 134 MPa

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

96

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

97

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl



Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation

Appendix 3

98

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator


OLKR12 - 403.68 mica gneiss dip of foliation 42° crack initiation: 55 ? MPa crack damage: 113 ? MPa

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

99

0

25

50

75

100

125

150

175

-0.30 % -0.20 % -0.10 % 0.00 % 0.10 % 0.20 % 0.30 % 0.40 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

100

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

101

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

102

0

25

50

75

100

125

150

175

-0.30 % -0.20 % -0.10 % 0.00 % 0.10 % 0.20 % 0.30 % 0.40 %

Strain ( % )

Axial Strain

Radial Strain

Actuator


OLKR12 - 573.02 mica gneiss dip of foliation 45° crack initiation: 83 ? MPa crack damage: 88 MPa

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

103

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

104

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

105

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

106

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 3

107

0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

Strain ( % )

Axial Strain

Radial Strain

Actuator



0

25

50

75

100

125

150

175

-0.3 % -0.2 % -0.1 % 0.0 % 0.1 % 0.2 % 0.3 % 0.4 %

A1_cir

A2_axi

A3_incl.

B2_axi

B1_cir

B3_incl

C1_axi

C2_cir

C3_incl

D2_circ

D1_axi

D3_incl

Strain ( % )

Stress ( MPa )

AB

C

D

axialinclined

circumferential

dip offoliation



Appendix 4 - page 1 108

Strength and Strain Anisotropy of Olkiluoto Mica greiss · Olkiluoto Mica greiss. Matti Hakala KMS...

Documents

Transcript of Strength and Strain Anisotropy of Olkiluoto Mica greiss · Olkiluoto Mica greiss. Matti Hakala KMS...