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Jacobsson, L. & Sjöström, J. (2019). Forsmark – Laboratory tests for investigation of the influence of rock type, oxidation, and other factors in borehole breakouts. Boreholes KFM01A, KFM04A, KFM05A and KFM24. Thermal properties by TPS method and uniaxial compression and indirect tensile strength tests of intact rock. Solna
Open this publication in new window or tab >>Forsmark – Laboratory tests for investigation of the influence of rock type, oxidation, and other factors in borehole breakouts. Boreholes KFM01A, KFM04A, KFM05A and KFM24. Thermal properties by TPS method and uniaxial compression and indirect tensile strength tests of intact rock
2019 (English)Report (Other academic)
Abstract [en]

The density, thermal and mechanical properties were determined on water saturated specimens from boreholes KFM01A, KFM04A, KFM05A and KFM24 in the Forsmark site investigation area. The tests have been concentrated to sections where borehole breakouts have been observed. The rock types in the selected sections were amphibolite (102017), granite to granodiorite (101057) and skarn (108018).

All specimens had a more or less foliated rock structure. The cores were sampled from a depth ranging between 308–929 m.

The specimens were water saturated using tap water and all subsequent measurements were conducted at this moisture condition. The density was determined on 41 specimens followed by measuring the thermal properties of 20 pairs of specimens. The thermal conductivity and diffusivity were measured and the volumetric heat capacity was calculated from the thermal conductivity and diffusivity. The testing ended with 35 indirect tensile tests yielding the indirect tensile strength and three uniaxial compression tests including the post-peak response yielded the Young’s modulus, Poisson ratio and the uniaxial compressive strength.

Three specimens aimed for the indirect tensile tests had a major crack and fell apart after measuring the density and the mechanical properties were not tested.

Some variation of rock material along the short cores could be seen, which is reflected in the measured data. The density at a water saturated condition was 2 640–2 814 kg/m3 for granite to granodiorite, 2 768–3 033 kg/m3 for amphibolite and 2 787–2 920 kg/m3 for skarn.

Thermal properties were measured at ambient temperature (22 °C) and under water saturated conditions. The determination of the thermal properties is based on a direct measurement method, the so called “Transient Plane Source Method” (TPS).

Thermal conductivity and thermal diffusivity at 22 °C were in the range of 1.6–3.5 W/(m, K) and 0.9–1.9 mm2/s, respectively. The volumetric heat capacity, which was calculated from the thermal conductivity and diffusivity, ranged between 1.6 and 2.6 MJ/(m3, K). Variations are most likely due to both depth and variations in rock type.

The indirect tensile tests were conducted such that every second specimen was tested with the diametrical compression along and every second across the foliation planes, with higher values for the indirect tensile strength on the specimens with loading across the foliation. The ratio between the strength measured on specimens with loading across over along the foliation was up to 1.6 for granodiorite and possible higher for the amphibolite. The strength variation in the amphibolite was large. The indirect tensile strength was 8.07–14.5 MPa for the granite to granodiorite, 1.18–16.2 MPa for amphibolite and 4.49–8.51 MPa for skarn.

Two of the uniaxial compression test specimens of amphibolite got a diagonal failure and the third had a spalling failure. The maximum axial compressive stress was 61.5 and 68.5 MPa for the specimens with a diagonal failure and 238.7 MPa for the specimen with a spalling failure. The Young’s modulus for the same specimens was 61.6 and 57.5 GPa, respectively 91.0 GPa and the Poisson ratio 0.288 and 0.407, respectively 0.375.

Abstract [sv]

Densiteten, termiska och mekaniska egenskaper har bestämts på vattenmättade prover from borrhål KFM01A, KFM04A, KFM05A och KFM24 i Forsmarks platsundersökningsområde. Provningarna har koncentrerats till avsnitt där s k ”borehole breakouts” har observerats. Bergarterna i de valda avsnitten är amfibolit (102017), granit till granodiorit (101057) och skarn (108018). Samtliga prover hade en mer eller mindre folierad bergstruktur. Proverna har tagits på djupnivåer mellan 308–929 m.

Proverna vattenmättades med kranvatten och alla efterföljande mätningar gjordes vid denna fukthalt. Densiteten mättes på samtliga 41 prover följt av mätning av de termiska egenskaperna på 20 par prover. Termisk konduktivitet och termisk diffusivitet mättes varefter den volumetriska värmekapaciteten beräknades. Provningen avslutades med 35 stycken indirekta test av draghållfastheten som gav den indirekta draghållfastheten och tre enaxiella kompressionsförsök inkluderat efterbrottsbeteende som gav värden på elasticitetsmodul, Poissons tal och enaxiell tryckhållfasthet.

Tre prover som var avsedda för indirekta dragförsök hade initialt en spricka och föll isär efter mätningen av densiteten och ingen mekanisk provning genomfördes.

En viss variation av bergmaterialet kunde ses på de korta kärnorna som visade sig i uppmätta data. Densiteten i ett vattenmättat tillstånd var 2 640–2 814 kg/m3 hos granit till granodiorit, 2 768–3 033 kg/m3 hos amfibolit och 2 787–2 920 kg/m3 hos skarn.

Termisk konduktivitet och termisk diffusivitet har bestämts vid rumstemperatur (22 °C) och vattenmättnad. Mätningarna av egenskaperna utfördes med den direkta metoden “Transient Plane Source” (TPS).

Termisk konduktivitet och termisk diffusivitet vid 22 °C bestämdes till 1.6–3.5 W/(m, K) respektive 0.9–1.9 mm2/s. Den volumetriska värmekapaciteten (produkten av densitet och specifk värmekapacitet), som beräknades från konduktivitet och diffusivitet, varierade mellan 1.6 and 2.6 MJ/(m3, K). Variationerna beror antagligen både på djup och på variationer i materialtyp.

De indirekta dragförsöken utfördes så att vartannat prov belastades med diametral kompression längs med och vartannat tvärs foliationsplanen. Kvoten mellan styrkan mätt med belastning tvärs och längs med foliationen var upp till 1,6 för granit till granodiorit och möjligen högre för amfibolit. Styrkevariationen var stor hos amfibolit. Den indirekta draghållfastheten var 8,07–14,5 MPa hos granit till granodoiorit, 1,18–16,2 MPa hos amfibolit, och 4,49–8,52 MPa hos skarn.

Vid de enaxiella kompressionsförsöken fick två av amfibolitproverna ett diagonalt brott och det tredje ett spjälkningsbrott. Den högsta axialspänningen var 61,5 och 68,5 MPa hos proverna som hade ett diagonalt brott och 238,7 MPa hos provet med ett spjälkningsbrott. Elasticitetsmoduluen var 61,6 och 57.5 GPa respektive 91,0 GPa och Poisson’s tal var 0,288 och 0,407 respektive 0,375.

Place, publisher, year, edition, pages
Solna: , 2019. p. 61
Series
SKB, ISSN 1651-4416 ; P-18-08
Keywords
Thermal properties, Uniaxial compression test, Tensile strength test
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-38175 (URN)
Funder
Swedish Nuclear Fuel and Waste Management Company, SKB
Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-03-13Bibliographically approved
Jacobsson, L., Kjell, G., Kiuru, R. & Suikkanen, J. (2019). Wave velocity measurements in three directions on axially loaded water-saturated granite and gneiss core specimens. In: Sergio A.B. da Fontoura, Ricardo José Rocca, José Félix Pavón Mendoza (Ed.), Proceedings of the 14th International congress on Rock Mechanics ans Rock Engineering (ISRM 2019), Foz do Iguassu, Brazil, 13-18 September 2019: Rock Mechanics for Natural Resources and Infrastructure Development. Paper presented at 14th International congress on Rock Mechanics ans Rock Engineering (ISRM 2019), Foz do Iguassu, Brazil, 13-18 September 2019 (pp. 1638-1645). Leiden, The Netherlands: CRC Press
Open this publication in new window or tab >>Wave velocity measurements in three directions on axially loaded water-saturated granite and gneiss core specimens
2019 (English)In: Proceedings of the 14th International congress on Rock Mechanics ans Rock Engineering (ISRM 2019), Foz do Iguassu, Brazil, 13-18 September 2019: Rock Mechanics for Natural Resources and Infrastructure Development / [ed] Sergio A.B. da Fontoura, Ricardo José Rocca, José Félix Pavón Mendoza, Leiden, The Netherlands: CRC Press, 2019, p. 1638-1645Conference paper, Published paper (Refereed)
Abstract [en]

The density, porosity and mechanical properties from uniaxial compression and Brazilian tests along with measurements of the P- and S-wave velocities in axial and two lateral directions at unloaded state and at increasing axial load were conducted on cylindrical cores of veined gneiss and granitic pegmatoid. The specimens were sampled close to a tunnel wall (0.1– 1.7 m depth) with the aim to find if there is an increasing amount of microcracks due to the excavation in a zone near the surface. Evidence of microcracks was found via the mechanical tests and the wave velocity measurements, due to increased mechanical stiffness and increasing wave velocities at loading. Anisotropy in in the gneiss specimens and also in the granitic pegmatoid was detected and measured via strain and wave velocity measurements. No clear evidence was found of increased amount of microcracks closer to the tunnel wall.

Place, publisher, year, edition, pages
Leiden, The Netherlands: CRC Press, 2019
Series
Proceedings in Earth and Geosciences, ISSN 2639-7749, E-ISSN 2629-7757 ; Volume 6
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-39951 (URN)978-0-367-42284-4 (ISBN)978-0-367-82317-7 (ISBN)
Conference
14th International congress on Rock Mechanics ans Rock Engineering (ISRM 2019), Foz do Iguassu, Brazil, 13-18 September 2019
Available from: 2019-09-22 Created: 2019-09-22 Last updated: 2019-10-14Bibliographically approved
Jacobsson, L. & Lindqvist, J. E. (2018). Laboratory investigation of crack initiation on hourglass-shaped granite specimens. In: Vladimir Litvinenko (Ed.), Geomechanics and Geodynamics of Rock Masses, Volume 1: Proceedings of the 2018 European Rock Mechanics Symposuim: . Paper presented at EUROCK 2018, Saint Petersburg, Russia, 22-26 May, 2018 (pp. 633-638). London: CRC Press
Open this publication in new window or tab >>Laboratory investigation of crack initiation on hourglass-shaped granite specimens
2018 (English)In: Geomechanics and Geodynamics of Rock Masses, Volume 1: Proceedings of the 2018 European Rock Mechanics Symposuim / [ed] Vladimir Litvinenko, London: CRC Press, 2018, p. 633-638Conference paper, Published paper (Refereed)
Abstract [en]

Laboratory experiments on axially compressed hourglass-shaped specimens of medium to coarse grained granite specimens were conducted. A tangential stress is generated in the circular notches which is intended to initiate surface spalling similar to what can be seen at circular openings in a rock mass. Specimens of three different sizes were tested with notch radii 98.4, 225 and 375 mm, which are equivalent to a hole diameter of 197, 450 and 750 mm. The spalling initiation and progress in the notches were monitored by acoustic emission and digital correlation measurements. From the acoustic emission measurements it could be seen that the tangential stress at spalling initiation decreased with increasing notch radius. Results from digital image correlation show how the surfaces in local zones in the notch were pushed outwards due to subsurface cracking parallel to the notch surface. Analyses of thin sections and polished slabs taken in the notch area showed that the cracking depth increased with increasing notch radius.

Place, publisher, year, edition, pages
London: CRC Press, 2018
Keywords
Cracks, Granite, Rock mechanics, Spalling, Acoustic emission measurement, Circular notches, Digital correlation, Digital image correlations, Laboratory experiments, Laboratory investigations, Surface spalling, Tangential stress, Acoustic emission testing
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-33926 (URN)2-s2.0-85061368041 (Scopus ID)9780429461774 (ISBN)9780429867729 (ISBN)
Conference
EUROCK 2018, Saint Petersburg, Russia, 22-26 May, 2018
Available from: 2018-06-02 Created: 2018-06-02 Last updated: 2019-03-19Bibliographically approved
Jacobsson, L., Appelquist, K., Lindqvist, J. E. & Åkesson, U. (2018). Spalling initiation experimentson large hard rock cores. Solna: Svensk Kärnbränslehantering AB
Open this publication in new window or tab >>Spalling initiation experimentson large hard rock cores
2018 (English)Report (Refereed)
Abstract [en]

A new type of laboratory test method to determine spalling resistance in a situation as in large boreholes in hard rock has been demonstrated. Uniaxial compression tests on large cores with notches were conducted on Äspö diorite from Äspö HRL. Spalling was localized to the notches where the local stress was highest. The crack initiation, crack coalescence and crack damage stresses representing various fracture stages were identified by using acoustic emission monitoring with source localization. The actual stress levels were obtained from the axial forces at which the various fracture stages were identified via FE-calculations representing the actual specimen geometry and loading. The results were compared with uniaxial compression tests carried out on cores with standard size on the same rock type also from Äspö HRL.

The results showed that spalling chips were formed similar to those found in field which indicates that the test is representing a realistic behaviour. However, the results show that the various fracture stress levels found in the tests are higher than the spalling strength found in the field and in the test of small cores. The higher stress levels could be caused by a number of reasons described in the report.

A post characterization of the fractures was carried out on slabs that were cut out from the specimens containing the notch areas. The occurrence of microcracks and how they have propagated through the different minerals and the location in relation to the notches, minerals and grain boundaries were investigated. The patterns of the major fractures and the secondary fractures were analysed. The majority seem to be extension fractures, but shearing could also be verified. The results from the microscopy analysis provide invaluable information of the spalling process at all stages.

Abstract [sv]

En ny typ av laboratorieprovmetod för att bestämma spjälkningsmotstånd i en situation som i stora borrhål i hårt berg har demonstrerats. Enaxiella kompressionsförsök på stora kärnor med notchar (urtag) genomfördes på Äspödiorit från Äspö HRL. Spjälkning lokaliserades till notcharna där den lokala spänningen var högst. Sprickinitierings-, spricksammanslagnings-, och sprickskadespänningen som representerar olika sprickstadier identifierades genom att använda akustisk emmissionsmätningar med lokalisering av källan. De aktuella spänningsnivåerna erhölls från den axiella kraften som de olika sprick stadierna identifierades via FE-beräkningar som representerar det aktuella provets geometri och belastning. Resultaten jämfördes med enaxiella kompressionsförsök som genomförts på borrkärnor med standardstorlek och bergart också från Äspö HRL.

Resultaten visade att spjälkningsbitar bildades liknande sådana som funnits i fält vilket indikerar att provet representerar ett realistiskt beteende. Emellertid visar resultaten att spänningarna vid de olika sprickstadierna i proven är högre än spjälkningshållfastheten som man har funnit i fält och i proven av de små kärnorna. De högre spänningsvärdena kan bero på ett antal orsaker som beskrivs i rapporten.

En post-karaktärisering av sprickorna genomfördes på skivor som sågades ut från proverna innehållande notch-områdena. Förekomsten av mikrosprickor och hur de har växt till genom de olika mineralerna och deras läge i förhållande till notcharna, mineralerna och korngränserna undersöktes. Mönstren av de huvudsakliga sprickorna och de sekundära sprickorna analyserades. Merparten verkar vara dragsprickor men skjuvning kunde också påvisas. Resultaten från mikroskopiundersökningarna ger ovärderlig information om spjälkningsprocessen vid alla stadier.

Place, publisher, year, edition, pages
Solna: Svensk Kärnbränslehantering AB, 2018. p. 68
Series
SKB, ISSN 1402-3091 ; R-14-12
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-33854 (URN)
Funder
Swedish Nuclear Fuel and Waste Management Company, SKB
Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2018-08-22Bibliographically approved
Jacobsson, L., Sandström, J. & Brander, L. (2018). Wedge splitting tests on granite and gneiss specimens. In: : . Paper presented at ARMS10 10th Asian Rock Mechanics Symposium The ISRM International Symposium for 2018, 29 Oct - 3 Nov, Singapore.
Open this publication in new window or tab >>Wedge splitting tests on granite and gneiss specimens
2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The conditions for initial tensile cracking around a rounded blunt and a sharp notch and subsequent propagation were investigated by means of wedge splitting tests on structurally isotropic granite. In addition, the crack initiation and propagation on anisotropic gneiss specimens with a blunt notch were investigated in two different material directions. The wedge splitting test specimens which has a straight notch is normally used to determine mode I fracture properties for concrete but not for rock materials. The use of a straight notch in the specimens instead of a chevron type of notch, which is commonly used for fracture mechanics tests, was found to be well suited for the actual type of investigation. 

The development of fractures from the notch into the specimens was monitored by measuring the deformation field on the specimen surface by digital image correlation (DIC) and by the crack mouth opening displacement. The fracture patterns were different in the granite and the gneiss. The DIC illustratively showed how cracks branched along the main crack path in the granite whereas no branching occurred in the gneiss material. This could also be verified by studying thin sections taken along the fracture path. It was seen that the granite behaved more ductile than the gneiss. 

A finite element model of the wedge splitting test was made where the crack propagation was modelled using a cohesive-zone model and calibrated using the results from the experiments. The fracture energies were computed and it was found that the energies were about 50-100 percent higher in the granite than in the gneiss. The tensile stress cracking initiation in granite for the blunt and the sharp notch was slightly different. The gneiss specimens were all with a blunt notch and a comparison of the two notch types could not be made in this case.

Keywords
Mode I fracture mechanics, Digital image correlation, Fracture energy, Fracture pattern
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36978 (URN)2-s2.0-85064274967 (Scopus ID)978-981-11-9003-2 (ISBN)
Conference
ARMS10 10th Asian Rock Mechanics Symposium The ISRM International Symposium for 2018, 29 Oct - 3 Nov, Singapore
Available from: 2019-01-03 Created: 2019-01-03 Last updated: 2019-05-10Bibliographically approved
Jacobsson, L. & Kjell, G. (2017). Measurement of p- and s-wave velocity in material using ultrasonics.
Open this publication in new window or tab >>Measurement of p- and s-wave velocity in material using ultrasonics
2017 (English)Report (Other academic)
Abstract [en]

The velocities of propagating elastic waves can be used to determine the amount of damage in form of induced microcracks in rock materials and other materials. An increasing number of microcracks yields lower propagation velocities. To assess the damage, e.g. around tunnels caused by the excavation, is of interest since the damage affects the material properties, such as mechanical and thermal properties and permeability.

A new ultrasonic testing system ULT-100 from GCTS (Geotechnical Consulting and Testing Systems), aimed for measurement of p- and s-wave velocities, was evaluated. Reference cylindrical specimens in aluminium with different sizes were manufactured and a series of tests were conducted in order to find suitable wave arrival picking methods and to determine equipment specific constants which are needed to be determined. The procedure to do this was according to an ASTM standard.

Expanded measurement uncertainties for the wave velocity measurements were calculated according to Guide to the Expression of Uncertainty in Measurement (GUM).

Equipment such as sensor holders and fixtures were manufactured in order to be able to conduct repeatable measurement on specimens. One test rig was made to carry out tests on nearly unloaded specimens in one direction and another was made for tests on axially loaded cylinders in a standard load frame with measurements in the axial plus two lateral directions.

A Round Robin test was carried out on the three different types of testing equipment, one at SP, one at Swedish Cement and Concrete Research Institute (CBI), and one at Finnish Geological Survey (GTK) in Finland to evaluate the measurement results on p-wave velocity measurements. The results of the measurements were mainly in line with the calculated measurement uncertainties.

The report is directed to persons working with wave velocity measurements using ultrasonics with particular interest of quality assurance of the measurements, which includes calibration, validation and uncertainty estimation.

Publisher
p. 145
Series
RISE Rapport ; 2017:48
Keywords
wave velocity, p-wave, s-wave, ultrasonic, piezoelectric, laboratory experiment
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-32443 (URN)978-91-88695-12-3 (ISBN)
Available from: 2017-10-31 Created: 2017-10-31 Last updated: 2018-06-27Bibliographically approved
Jacobsson, L. (2017). Storskaliga labförsök för ökad förståelse av spjälkningsprocessen. In: Svenska Bergmekanikgruppens höstseminarium, 29 november 2017 på Äspölaboratoriet: Bergmekanisk forskning vid Äspölaboratoriet – historiska framsteg och framtida utmaningar. Paper presented at Svenska Bergmekanikgruppens höstseminarium.
Open this publication in new window or tab >>Storskaliga labförsök för ökad förståelse av spjälkningsprocessen
2017 (Swedish)In: Svenska Bergmekanikgruppens höstseminarium, 29 november 2017 på Äspölaboratoriet: Bergmekanisk forskning vid Äspölaboratoriet – historiska framsteg och framtida utmaningar, 2017Conference paper, Oral presentation only (Other academic)
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-32910 (URN)
Conference
Svenska Bergmekanikgruppens höstseminarium
Funder
Swedish Nuclear Fuel and Waste Management Company, SKB
Available from: 2017-12-24 Created: 2017-12-24 Last updated: 2018-06-27Bibliographically approved
Jacobsson, L., Flansbjer, M., Andersson, L. & Appelquist, K. (2016). Normal Loading and Shear Tests on Rock.
Open this publication in new window or tab >>Normal Loading and Shear Tests on Rock
2016 (English)Report (Other academic)
Publisher
p. 138
Series
Posiva working report ; 2016:30
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-27933 (URN)
Available from: 2017-01-20 Created: 2017-01-20 Last updated: 2018-08-22Bibliographically approved
Jacobsson, L., Flansbjer, M., Andersson, L. & Appelquist, K. (2016). Normal Loading and Shear Tests on Rock Joints from Olkiluoto. Posiva Oy, Finland
Open this publication in new window or tab >>Normal Loading and Shear Tests on Rock Joints from Olkiluoto
2016 (English)Report (Other academic)
Place, publisher, year, edition, pages
Posiva Oy, Finland: , 2016. p. 130
Series
POSIVA Report ; 30
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-28338 (URN)
Available from: 2017-03-07 Created: 2017-03-07 Last updated: 2018-08-22Bibliographically approved
Jacobsson, L., Flansbjer, M., Johannesson, P., Lindqvist, J.-E., Brander, L. & Schouenborg, B. (2016). ONKALO POSE Experiment - Geological and Rock Mechanical Tests on Samples from a Heating Test at Olkiluoto.
Open this publication in new window or tab >>ONKALO POSE Experiment - Geological and Rock Mechanical Tests on Samples from a Heating Test at Olkiluoto
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2016 (English)Report (Other academic)
Series
POSIVA Working Report ; 2016:18
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-28342 (URN)
Available from: 2017-03-07 Created: 2017-03-07 Last updated: 2018-08-22Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4526-4061

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