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  • 101.
    Jacobsson, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Flansbjer, Mathias
    Borehole KLX13A. Shear tests on sealed joints. Oskarshamn site investigation2006Report (Refereed)
  • 102.
    Jacobsson, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Flansbjer, Mathias
    Äspö Pillar Stability Experiment. Samples from TASQ tunnel at Äspö HRL. Normal loading and shear tests on joints2005Report (Refereed)
  • 103.
    Jacobsson, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Flansbjer, Mathias
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Andersson, Lars
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Appelquist, Karin
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Normal Loading and Shear Tests on Rock2016Report (Other academic)
  • 104.
    Jacobsson, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Flansbjer, Mathias
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Andersson, Lars
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Appelquist, Karin
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Normal Loading and Shear Tests on Rock Joints from Olkiluoto2016Report (Other academic)
  • 105.
    Jacobsson, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Flansbjer, Mathias
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Brzovic, Andres
    de los Santos, Carlos
    Direct shear and tensile test on cemented healed joints from El Teniente mine, Chile2011In: Proceedings of the 12th ISRM International Congress on Rock Mechanics, 2011, , p. 649-654Conference paper (Refereed)
  • 106.
    Jacobsson, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Flansbjer, Mathias
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Jansson, Thomas
    Christiansson, Rolf
    Measurement of micro crack volume in low porosity crystalline rock2007In: Proceedings of the 11th ISRM Congress, 2007Conference paper (Refereed)
  • 107.
    Jacobsson, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Flansbjer, Mathias
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Johannesson, Pär
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Lindqvist, Jan-Erik
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Brander, Linus
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Schouenborg, Björn
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    ONKALO POSE Experiment - Geological and Rock Mechanical Tests on Samples from a Heating Test at Olkiluoto2016Report (Other academic)
  • 108.
    Jacobsson, Lars
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Flansbjer, Mathias
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Larsson, Jörgen
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Direct shear tests on large natural and artificially induced rock fractures in a new laboratory equipment2023In: Proceedings of the ISRM 15th International Congress on Rock Mechanics and Rock Engineering & 72nd Geomechanics Colloquium: Challenges in Rock Mechanics and Rock Engineering / [ed] Schubert, W. & Kluckner, A., Salzburg: Austrian Society for Geomechanics , 2023, p. 2709-2714, article id 1827Conference paper (Refereed)
    Abstract [en]

    A direct shear equipment for testing rock fractures up to 400×600 mm size, and up to 5 MN force in both normal and shear loading directions, was developed. Normal loading and direct shear tests under constant normal stiffness (CNS) and constant normal load (CNL) conditions were conducted on 300×500 mm specimens, one planar steel joint and two natural and two tensile induced rock fractures. Design targets, e.g. system to maintain undisturbed fractures up to testing and high system stiffnesses to achieve well-controlled shear tests, were verified by the experiments. A new optical system for local deformation measurements was used to accurately determine fracture displacements besides conventional non-local deformation measurements. The determined normal stiffnesses were similar previous results from the literature on smaller fractures, whereas the shear stiffness data are novel. The results provide a new insight into processes at the onset of fracture slip.

  • 109.
    Jacobsson, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Flansbjer, Mathias
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Schouenborg, Björn
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Grelk, Bent
    Smits, Arwen
    Expert System for Dimensioning of Facade Cladding2010In: Proceedings of Global Stone Congress 2010, 2010, , p. 1-4Conference paper (Refereed)
    Abstract [en]

    Proceedings of the Global Stone Congress 2010, Alicante Spain, 2-5 March 2010 2010 (Extern vetenskaplig bok)

  • 110.
    Jacobsson, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Glamheden, Rune
    Hakami, Eva
    Olofsson, Isabelle
    Rock mechanics laboratory testing in SKB site investigation program2012In: Proceedings of EUROCK 2012, 2012Conference paper (Refereed)
  • 111.
    Jacobsson, Lars
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Measuring the hydraulic transmissivity of a rock joint under varying normal load2022Conference paper (Refereed)
  • 112.
    Jacobsson, Lars
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Measuring the hydraulic transmissivity of a rock joint under varying normal load2023In: IOP Conference Series: Earth and Environmental Science, Institute of Physics , 2023, no 1Conference paper (Refereed)
    Abstract [en]

    The water flow rate through a rectangular granite specimen with a tight unopened natural induced joint of dimensions 200×200 mm was measured in two perpendicular directions. The measurements were conducted at five different levels of stress corresponding to loading from 0 to 8 MPa and unloading back to 0 MPa. The flow was measured at different hydraulic gradients in the range of 10 to 25. The results showed a joint transmissivity between 0.002-0.03 mm2/s and a hydraulic aperture of 8-32 μm. It was shown that the measurements performed in the second orientation displayed smaller transmissivity and hydraulic aperture as compared to those in the first orientation, showing a residual compaction after the first load cycle. The Reynolds number was less than one in all the measurements yielding laminar flow conditions. Deviations from the linear regime relationship were observed for the lowest flow rates (Re < 0.1). A transitory regime was observed when varying the hydraulic gradient. This regime was observed to be longer at the lowest flow rates. © 2023 Institute of Physics Publishing. All rights reserved.

  • 113.
    Jacobsson, Lars
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Ivars, D. M.
    SKB, Swedish Nuclear Fuel and Waste Management Company, Sweden; KTH Royal Institute of Technology, Sweden.
    Kasani, H. A.
    Nuclear Waste Management Organization, Canada.
    Johansson, F.
    KTH Royal Institute of Technology, Sweden.
    Lam, T.
    Nuclear Waste Management Organization, Canada.
    Experimental program on mechanical properties of large rock fractures2021In: IOP Conference Series: Earth and Environmental Science, IOP Publishing Ltd , 2021, Vol. 833, no 1, article id 012015Conference paper (Refereed)
    Abstract [en]

    Predictions of fracture displacements are required to support the safety assessments of a deep geological repository for nuclear spent fuel. Laboratory and in-situ experiments are used to estimate these properties. Despite significant contributions in the last decades, there is a knowledge gap in terms of the impact of high normal stresses on the mechanical properties of large-scale fractures under Constant Normal Stiffness (CNS) boundary conditions. Within the framework of the POST project, a cooperative effort was made by SKB (Sweden), NWMO (Canada), and Posiva from Finland (in phase 1) to study these questions. In the second phase of the POST project, a first of a kind direct shear testing machine was manufactured and calibrated that can accommodate samples up to 400 × 600 mm under normal stresses up to 10 MPa, for both CNS and Constant Normal Load (CNL) conditions, with the ability to shear the sample up to 50 mm. Several best practice procedures were developed for fracture characterization pre-, syn-, and post-shear test which utilize high resolution optical scanning, contact pressure measurements, Digital Image Correlation (DIC) measurements, and acoustic emission measurements during the shear test. Natural and tensile-induced fractures of a granitic rock as well as replicas of the hard rock fractures, at three different fracture sizes of 35×60 mm, 70×100 mm, and 300×500 mm, are now being tested. It is hoped that this program will provide a set of high-quality data which will help reduce the knowledge gap in the understanding of fracture behavior. 

  • 114.
    Jacobsson, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Karlsson, Linda
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Andersson, Hans
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Are methods for tightness testing fit for purpose?2012In: Proceedings of PPXVI, 2012Conference paper (Refereed)
  • 115.
    Jacobsson, Lars
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Kjell, Gunnar
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Measurement of p- and s-wave velocity in material using ultrasonics2017Report (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.

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  • 116.
    Jacobsson, Lars
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Kjell, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Brander, Linus
    RISE - Research Institutes of Sweden (2017-2019), Built Environment, CBI Swedish Cement and Concrete Research Institute.
    Kiuru, Risto
    Pöyry Finland Oy, Finland.
    EDZ Study Area in ONK-TKU-3620; Determination of Seismic Wave Velocities at Six Load Levels, Pethrophysical and Rock Mechanical Properties of Drill Core Specimens2019Report (Other academic)
    Abstract [en]

    Laboratory experiments on specimens from the excavation damaged zone area in the ONK-TKU-3620 were conducted. The experiments comprised density and porosity measurements, P- and S-wave velocity measurements at unloaded condition in one direction and at uniaxial compression in three orthogonal directions, indirect tensile tests and uniaxial compression tests on cylindrical specimens of veined gneiss (VGN) and granitic pegmatoid (PGR). All tests were conducted on saline (formation) water saturated specimens.

    The density and porosity measurements revealed a dependence of the saturation procedure between the one used at the Finnish Geological Survey and the one recommended by ISRM. It should be noted that the applied procedure deviated slightly from the procedure defined by the ISRM. The deviation decreased after saturating the specimens again by long-term immersion in water (5 weeks or more) and re-measuring the specimens in water saturated state. Increased porosity compared to the other tested specimens could be observed in one specimen that had a visually observable sealed joint. Some other specimens had a slightly increased deviating porosity.

    The wave velocities measured under loading in three directions showed anisotropy in almost all specimens. The anisotropy was expected in the structurally anisotropic VGN specimens. Anisotropy was also observed in the structurally isotropic PGR specimens. The anisotropy in this case may be either a weak foliation or oriented microfractures. The anisotropic wave velocity data match measured strains. The wave velocities for the VGN also match the response that is expected at transverse isotropy which is a suitable constitutive model assumption for the VGN.

  • 117.
    Jacobsson, Lars
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Kjell, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Kiuru, Risto
    Aalto University, Finland.
    Suikkanen, Johannes
    Posiva OY, Finland.
    Wave velocity measurements in three directions on axially loaded water-saturated granite and gneiss core specimens2019In: 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 (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.

  • 118.
    Jacobsson, Lars
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Lindqvist, Jan Erik
    RISE - Research Institutes of Sweden, Built Environment, CBI Swedish Cement and Concrete Research Institute.
    Laboratory investigation of crack initiation on hourglass-shaped granite specimens2018In: 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 (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.

  • 119.
    Jacobsson, Lars
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Lindqvist, Jan Erik
    RISE - Research Institutes of Sweden, Built Environment, CBI Swedish Cement and Concrete Research Institute.
    Laboratory investigation of stress gradient effect at spalling experiments on granite2015In: The 13th International Congress of Rock Mechanics: ISRM Congress 2015, 2015Conference paper (Refereed)
    Abstract [en]

    A series of laboratory tests were conducted to study stress-induced spalling on medium to coarse-grained granite specimens. The specimens made from cylinders had two manufactured notches on opposite sides aimed to represent the tangential loading around a circular opening. Specimens of three different sizes were tested with notch radii, 98.5, 225 and 375 mm, representing 197, 450 and 750 mm diameter holes, to study the effect of notch radius on the spalling initiation stress. The cracking was monitored by acoustic emission sampling. The fracture patterns were investigated visually on polished slabs and by microscopy on thin sections. The crack analysis describes how the cracks propagate in relation to the grain structure in the rock and to the macroscopic stress field.

  • 120.
    Jacobsson, Lars
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Mas Ivars, Diego
    SKB Swedish Nuclear Fuel and Waste Management Company, Sweden; KTH Royal Institute of Technology, Sweden.
    Kasani, Hossein A
    Nuclear Waste Management Organization, Canada.
    Johansson, Fredrik
    KTH Royal Institute of Technology, Sweden.
    Experimental program to study scale effects on mechanical properties of large rock fractures2022In: Abstract Volume, 2022, p. 102-103Conference paper (Other academic)
    Abstract [en]

    The scale effect of natural and artifically induced rock fractures and replicas up to a 500 mm length are experimentally studied by direct shear tests in a testing program including a newly manufactured large shear testing equipment. The fractures are chatacterised pre-, syn-, and post-shear test. Combinations of different measurements provide a high-quality dataset enabling deeper understanding of, and constitutive model development for rock fractures used for safety assessment of deep geological respoitories for nuclear waste disposal.

  • 121.
    Jacobsson, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Runesson, Kenneth
    Computational modelling of high-cycle deformation of railway ballast2002In: Proceedings  5th World Congress on Computational Mechanics (WCCM V), 2002, p. 12 pp-Conference paper (Other academic)
  • 122.
    Jacobsson, Lars
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Sandström, Johan
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Brander, Linus
    RISE - Research Institutes of Sweden (2017-2019), Built Environment, CBI Swedish Cement and Concrete Research Institute.
    Wedge splitting tests on granite and gneiss specimens2018Conference 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.

  • 123.
    Jacobsson, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Sandström, Johan
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Flansbjer, Mathias
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Sjögren, Torsten
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Brander, Linus
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    ONKALO POSE Experiment - Laboratory Determination of Density, Porosity and Mechanical Anisotropy of Gneiss and Granite2016Report (Other academic)
  • 124.
    Jacobsson, Lars
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Sjöström, Johan
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    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 rock2019Report (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.

  • 125.
    Johannesson, Pär
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Svensson, Thomas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Hållfasthet (BMh).
    Jacobsson, Lars
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Bygg och Mekanik, Strukturer och Komponenter.
    Bokesjö, Mathias
    RISE, SP – Sveriges Tekniska Forskningsinstitut, AstaZero.
    Olsson, L
    VMEA-metoden för bedömning av osäkerheter i bergmekaniska tillämpningar. The VMEA-method for Assessing Uncertainties in Rock Engineering2013Report (Other academic)
  • 126.
    Kiuru, R.
    et al.
    Aalto University School of Engineering, Finland.
    Jacobsson, Lars
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Király, D.
    SOM System Kft, Hungary.
    Suikkanen, J.
    Posiva Oy, Finland.
    Effects of Excavation Damage on the Physical Properties of Rock Matrix2021In: IOP Conference Series: Earth and Environmental Science, IOP Publishing Ltd , 2021, Vol. 833, no 1, article id 012020Conference paper (Refereed)
    Abstract [en]

    Posiva Oy has conducted investigations into excavation damage, including comprehensive laboratory testing of physical properties of rock specimens from excavation damaged rock mass. Laboratory testing was conducted on drill core specimens extracted from the excavated surface of a tunnel located at approximately 345 m depth in Olkiluoto, Finland. A total of 141 drill core specimens of three main rock types, a structurally isotropic coarse-grained pegmatoid (PGR) and structurally anisotropic veined gneiss (VGN) and diatexitic gneiss (DGN), were subjected to petrophysical testing, rock mechanics testing and petrographic analyses. Results from the various tests were subjected to rigorous statistical analysis in order to reveal the effects excavation damage has on the physical properties of the rock mass. Results of the study revealed changes that are credited to excavation damage in resistivity, S-wave velocity and various elastic properties of the rock specimens. Effects of excavation damage and the depth of the excavation damaged zone seem to be different to gneiss compared to pegmatoid. On microscopic level, the extent of excavation damaged zone appears to be 0.2 - 0.4 m depending on the measured property. This means that the deeper excavation damaged layer observed by geophysical surveys may be caused by larger scale fractures. 

  • 127.
    Kiuru, Risto
    et al.
    Geofcon, Finland.
    Heikkinen, Eero
    Pöyry Finland Oy, Finland.
    Jacobsson, Lars
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Kovacs, Dorottya
    University of Szeged, Hungary.
    EDZ Study Area in ONK-TKU-3620: Petrophysical, Rock Mechanics and Petrographic Testing and Analysis Conducted on Drill Core Specimens between 2014 and 20162019Report (Other academic)
    Abstract [en]

    Physical and mechanical properties of drill core specimens were determined as a part of investigations into excavation damage in the dedicated study area in ONK-TKU-3620. Additionally, microfractures in 16 specimens from drillholes ONK-SH32 and ONK-SH39 were analysed and used as a basis for fractals based discrete fracture network modelling.

    Best indicators for excavation damage, based on this study, would appear to be resistivity, S-wave velocity, and elastic parameters that are derived from S-wave velocity. The effects seemed to be mostly limited to pegmatoid specimens. Same properties also distinguished anomalous specimens, typically from shallow depths, some of which could be directly linked to visible EDZ features. 

    Comparing the crack initiation stress values to prior data from specimens saturated with non-saline water, similar results were obtained. This suggests that whatever chemical corrosion the saline water may have inflicted on the specimens has happened prior to sampling in situ, and that the decrease in strength compared to dry specimens is mainly due to water content, rather than the type of water.

    It was concluded that the difference in resistivity between pegmatoid and gneissic specimens of similar porosity was likely due to differences in the types of microfractures. This hypothesis was later confirmed from the thin sections and simulation: fractures in VGN were short and mostly in one preferred orientation, whereas the fractures in PGR were longer and had two preferred orientations. This suggests that VGN and PGR may suffer different types of excavation damage. Based on simulation results, the number of large fracture clusters and maximum number of fractures per cluster seem to increase with increasing volumetric PGR content. The interconnectivity of microfractures however seems to be negligible.

    No depth dependencies in geometric parameters of the microfractures were observed, while differences between VGN and PGR were observed. This suggests that excavation does not cause detectable disturbance of the intact rocks’ microfracture porosity, and that the disturbed layer observed by geophysical methods may be caused by larger scale fractures not present in the relatively intact specimens.

  • 128.
    Kiuru, Risto
    et al.
    Aalto University, Finland.
    Jacobsson, Lars
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Király, Dorka
    Budapest University of Technology and Economics, Hungary.
    Suikkanen, Johannes
    Posiva Oy, Finland.
    Geofysiikka louhintavauriotutkimuksissa2022In: XXX Geofysiikan päivät: Helsingissä 18.‐19.5.2022, Helsingfors: Geofysiikan Seura , 2022, p. 34-35Conference paper (Other academic)
  • 129.
    Kiuru, Risto
    et al.
    Aalto University, Finland.
    Jacobsson, Lars
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Király, Dorottya
    Suikkanen, Johannes
    Louhintavaurion vaikutus kalliomassan fysikaalisiin ominaisuuksiin2021In: Conference proceedings of the XXIII Sovelletun geofysiikan neuvottelupäivät in Espoo, Finland, 23.‐24.11.2021., 2021Conference paper (Other academic)
  • 130.
    Kiuru, Risto
    et al.
    Aalto University, Finland.
    Király, Dorka
    Budapest University, Hungary.
    Dabi, Gergely
    University of Szeged, Hungary.
    Jacobsson, Lars
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Comparison of dfn modelled microfracture systems with petrophysical data in excavation damaged zone2021In: Applied Sciences, E-ISSN 2076-3417, Vol. 11, no 7, article id 2899Article in journal (Refereed)
    Abstract [en]

    Physical and petrographic properties of drill core specimens were determined as a part of investigations into excavation damage in the dedicated study area in the ONKALO® research facility in Olkiluoto, Western Finland. Microfractures in 16 specimens from two drillholes were analysed and used as a basis for fractal geometry-based discrete fracture network (DFN) modelling. It was concluded that the difference in resistivity between pegmatoid granite (PGR) and veined gneiss (VGN) specimens of similar porosity was likely due to differences in the types of microfractures. This hypothesis was confirmed from microfracture analysis and simulation: fractures in gneiss were short and mostly in one preferred orientation, whereas the fractures in granite were longer and had two preferred orientations. This may be due to microstructure differences of the rock types or could suggests that gneiss and granite may suffer different types of excavation damage. No dependencies on depth from the excavated surface were observed in the geometric parameters of the microfractures. This suggests that the excavation damaged zone cannot be identified based on the changes in the parameters of the microfracture networks, and that the disturbed layer observed by geophysical methods may be caused by macro-scale fractures. © 2021 by the authors.

  • 131.
    Lägermo, Caroline
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Jacobsson, Lars
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Sjöström, Johan
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Sokoti, Hasan
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Lindström, Camilla
    RISE Research Institutes of Sweden, Built Environment, Infrastructure and concrete technology.
    Forsmark – Laboratory tests in borehole KFM24 : Thermal properties by TPS method and indirect tensile strength tests with strain measurements of intact rock2021Report (Other academic)
    Abstract [en]

    The density, thermal and mechanical properties were determined on water-saturated specimens from borehole KFM24 in the Forsmark site investigation area. The rock type was granite to granodiorite (101057). All specimens had a more or less foliated rock structure. The cores were sampled from depths ranging between 65–526 m. The specimens were water-saturated using tap water and all subsequent measurements were conducted at this moisture condition. The density was determined on 25 specimens followed by measuring the thermal properties of 9 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 21 indirect tensile tests yielding the indirect tensile strength. The strain was measured using strain gauges during the indirect tensile tests. The density at a water-saturated condition was 2648–2694 kg/m3 . Thermal properties were measured at ambient temperature (23°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 23°C were in the range of 3.1–3.8 W/(m, K) and 1.8–2.0 mm2 /s, respectively. The volumetric heat capacity, which was calculated from the thermal conductivity and diffusivity, ranged between 1.8 and 2.3 MJ/(m3 , K). The indirect tensile tests were conducted with the diametrical compression across the foliation planes. The indirect tensile strength was in the range 9.7–16.5 MPa

  • 132.
    Pérez-Rey, Ignacio
    et al.
    Universidade de Vigo, Spain; KTH Royal Institute of Technology, Sweden.
    Muñiz-Menéndez, Mauro
    Laboratorio de Geotecnia, Spain.
    Frühwirt, Thomas
    Graz University of Technology, Austria.
    Konietzky, Heinz
    TU Bergakademie Freiberg, Germany.
    Jacobsson, Lars
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Perras, Matthew A.
    York University, Canada.
    Atefi-Monfared, Kamelia
    York University, Canada.
    Mas Ivars, Diego
    SKB Swedish Nuclear Fuel and Waste Management Co, Sweden; KTH Royal Institute of Technology, Sweden.
    Sánchez Juncal, Abel
    SKB Swedish Nuclear Fuel and Waste Management Co, Sweden.
    Alejano, Leandro R.
    Universidade de Vigo, Spain.
    Assessment of Direct Tensile Strength Tests in Rock Through a Multi-laboratory Benchmark Experiment2024In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453XArticle in journal (Refereed)
    Abstract [en]

    This study aims to experimentally assess repeatability and reproducibility of direct tensile strength (DTS) tests with deformability measurements on two types of rocks: Blanco Mera granite (Spain) and Cotta sandstone (Germany). The tests were conducted in four rock mechanics laboratories located in different countries (Canada, Germany, Spain and Sweden). A total of 51 tests were performed on cylindrical specimens of the two rocks, using different test equipment and measuring devices. Mean and standard deviation DTS values were determined in the four laboratories for the granite (5.70 ± 0.32, 6.06 ± 0.11, 3.84 ± 0.50 and 6.76 ± 0.10 MPa) and for the sandstone (1.88 ± 0.07, 1.96 ± 0.06, 1.15 ± 0.32 and 1.74 ± 0.19 MPa), together with Young’s moduli and Poisson’s ratios in tension, being statistically analysed to evaluate the variability and compare the main results obtained from the participating laboratories. The findings indicate that the DTS test with deformability measurements on cylindrical rock specimens is operationally feasible. However, certain shortcomings have been identified during the course of the experiments with the existing methodologies, such as the one suggested by the ISRM for DTS tests. The results have also shown to be sensitive to appropriate test and strain measurement configurations. The objective of this study was to shed light on these issues and provide new insights for potential future improvements of the existing testing methods.

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