Non-invasive detection of fractures, fracture zones, and rock damage in a hard rock excavation — Experience from the Äspö Hard Rock Laboratory in Sweden

2015 ◽  
Vol 196 ◽  
pp. 210-221 ◽  
Author(s):  
G. Walton ◽  
M. Lato ◽  
H. Anschütz ◽  
M.A. Perras ◽  
M.S. Diederichs
Keyword(s):  
Hard Rock ◽  
Rock Damage ◽  
Fracture Zones ◽  
Rock Excavation ◽  
Non Invasive ◽  
Rock Laboratory

scholarly journals Electric resistivity and seismic refraction tomography, a challenging joint underwater survey at Äspö Hard Rock Laboratory

2016 ◽  
Author(s):  
Mathias Ronczka ◽  
Kristofer Hellman ◽  
Thomas Günther ◽  
Roger Wisen ◽  
Torleif Dahlin
Keyword(s):  
Nuclear Power ◽  
Hard Rock ◽  
Seismic Refraction ◽  
Three Dimensional ◽  
Test Site ◽  
Fracture Zones ◽  
Rock Laboratory ◽  
Refraction Tomography ◽  
Local Point ◽  
General Test

Abstract. Tunnelling below water passages is a challenging task in terms of planning, pre-investigation and construction. Fracture zones in the underlying bedrock lead to low rock quality and thus reduced stability. For natural reasons they tend to be more frequent at water passages. Ground investigations that provide information of the subsurface are necessary prior to the construction phase, but can be logistically difficult. Geophysics can help close the gaps between local point information and produce subsurface images. An approach that combines seismic refraction tomography and electrical resistivity tomography has been tested at the Äspö Hard Rock Laboratory (HRL). The aim was to detect fracture zones in a well-known but logistically and, from a measuring perspective, challenging area. The presented surveys cover a water passage along a part of a tunnel that connects surface facilities with an underground test laboratory. The tunnel is approximately 100 m below and 20 m east of the survey line and gives evidence for one major and several minor fracture zones. The geological and general test site conditions, e.g. with strong powerline noise from the nearby nuclear power plant, are challenging for geophysical measurements. Co-located positions for seismic and ERT sensors and source positions are used on the 450 m long underwater section of the 700 m long profile. Because of a large transition zone that appeared in the ERT result and the missing coverage of the seismic data, fracture zones at the southern and northern part of the underwater passage cannot be detected by separated inversion. A simple synthetic study shows significant three dimensional artefacts corrupting the ERT model that have to be taken into account while interpreting the results. A structural coupling cooperative inversion approach is able to image the northern fracture zone successfully. In addition, previously unknown sedimentary deposits with a significant large thickness are detected in the otherwise unusually well documented geological environment. The results significantly improve imaging of some geologic features, which would have been not detected or misinterpreted otherwise, and combines the images by means of cluster analysis to a conceptual subsurface model.

scholarly journals Boat-towed radio-magnetotelluric and controlled source audio-magnetotelluric study to resolve fracture zones at Äspö Hard Rock Laboratory site, Sweden

2019 ◽  
Vol 218 (2) ◽  
pp. 1008-1031 ◽  
Author(s):  
Shunguo Wang ◽  
Mehrdad Bastani ◽  
Steven Constable ◽  
Thomas Kalscheuer ◽  
Alireza Malehmir
Keyword(s):  
Shallow Water ◽  
Penetration Depth ◽  
Large Scale ◽  
Hard Rock ◽  
High Water ◽  
Fracture Zones ◽  
Geological Structures ◽  
Near Surface ◽  
Controlled Source ◽  
Rock Laboratory

SUMMARY Boat-towed radio-magnetotelluric (RMT) measurements using signals between 14 and 250 kHz have attracted increasing attention in the near-surface applications for shallow water and archipelago areas. A few large-scale underground infrastructure projects, such as the Stockholm bypass in Sweden, are planned to pass underneath such water zones. However, in cases with high water salinity, RMT signals have a penetration depth of a few metres and do not reach the geological structures of interest in the underlying sediments and bedrock. To overcome this problem, controlled source signals at lower frequencies of 1.25 to 12.5 kHz can be utilized to improve the penetration depth and to enhance the resolution for modelling deeper underwater structures. Joint utilization of boat-towed RMT and controlled source audio-magnetotellurics (CSAMT) was tested for the first time at the Äspö Hard Rock Laboratory (HRL) site in south-eastern Sweden to demonstrate acquisition efficiency and improved resolution to model fracture zones along a 600-m long profile. Pronounced galvanic distortion effects observed in 1-D inversion models of the CSAMT data as well as the predominantly 2-D geological structures at this site motivated usage of 2-D inversion. Two standard academic inversion codes, EMILIA and MARE2DEM, were used to invert the RMT and CSAMT data. EMILIA, an object-oriented Gauss–Newton inversion code with modules for 2-D finite difference and 1-D semi-analytical solutions, was used to invert the RMT and CSAMT data separately and jointly under the plane-wave approximation for 2-D models. MARE2DEM, a Gauss–Newton inversion code for controlled source electromagnetic 2.5-D finite element solution, was modified to allow for inversions of RMT and CSAMT data accounting for source effects. Results of EMILIA and MARE2DEM reveal the previously known fracture zones in the models. The 2-D joint inversions of RMT and CSAMT data carried out with EMILIA and MARE2DEM show clear improvement compared with 2-D single inversions, especially in imaging uncertain fracture zones analysed in a previous study. Our results show that boat-towed RMT and CSAMT data acquisition systems can be utilized for detailed 2-D or 3-D surveys to characterize near-surface structures underneath shallow water areas. Potential future applications may include geo-engineering, geohazard investigations and mineral exploration.

scholarly journals Electric resistivity and seismic refraction tomography: a challenging joint underwater survey at Äspö Hard Rock Laboratory

Solid Earth ◽  
2017 ◽  
Vol 8 (3) ◽  
pp. 671-682 ◽  
Author(s):  
Mathias Ronczka ◽  
Kristofer Hellman ◽  
Thomas Günther ◽  
Roger Wisén ◽  
Torleif Dahlin
Keyword(s):  
Nuclear Power ◽  
Hard Rock ◽  
Seismic Refraction ◽  
Three Dimensional ◽  
Test Site ◽  
Fracture Zones ◽  
Rock Laboratory ◽  
Refraction Tomography ◽  
Local Point ◽  
General Test

Abstract. Tunnelling below water passages is a challenging task in terms of planning, pre-investigation and construction. Fracture zones in the underlying bedrock lead to low rock quality and thus reduced stability. For natural reasons, they tend to be more frequent at water passages. Ground investigations that provide information on the subsurface are necessary prior to the construction phase, but these can be logistically difficult. Geophysics can help close the gaps between local point information by producing subsurface images. An approach that combines seismic refraction tomography and electrical resistivity tomography has been tested at the Äspö Hard Rock Laboratory (HRL). The aim was to detect fracture zones in a well-known but logistically challenging area from a measuring perspective. The presented surveys cover a water passage along part of a tunnel that connects surface facilities with an underground test laboratory. The tunnel is approximately 100 m below and 20 m east of the survey line and gives evidence for one major and several minor fracture zones. The geological and general test site conditions, e.g. with strong power line noise from the nearby nuclear power plant, are challenging for geophysical measurements. Co-located positions for seismic and ERT sensors and source positions are used on the 450 m underwater section of the 700 m profile. Because of a large transition zone that appeared in the ERT result and the missing coverage of the seismic data, fracture zones at the southern and northern parts of the underwater passage cannot be detected by separated inversion. Synthetic studies show that significant three-dimensional (3-D) artefacts occur in the ERT model that even exceed the positioning errors of underwater electrodes. The model coverage is closely connected to the resolution and can be used to display the model uncertainty by introducing thresholds to fade-out regions of medium and low resolution. A structural coupling cooperative inversion approach is able to image the northern fracture zone successfully. In addition, previously unknown sedimentary deposits with a significantly large thickness are detected in the otherwise unusually well-documented geological environment. The results significantly improve the imaging of some geologic features, which would have been undetected or misinterpreted otherwise, and combines the images by means of cluster analysis into a conceptual subsurface model.

scholarly journals Viruses in granitic groundwater from 69 to 450 m depth of the Äspö hard rock laboratory, Sweden

2008 ◽  
Vol 2 (5) ◽  
pp. 571-574 ◽  
Author(s):  
Jennifer E Kyle ◽  
Hallgerd S C Eydal ◽  
F Grant Ferris ◽  
Karsten Pedersen
Keyword(s):  
Hard Rock ◽  
Rock Laboratory ◽  
Granitic Groundwater

Modelling the Prototype Repository

2018 ◽  
Vol 482 (1) ◽  
pp. 241-260 ◽  
Author(s):  
V. Tsitsopoulos ◽  
S. Baxter ◽  
D. Holton ◽  
J. Dodd ◽  
S. Williams ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Host Rock ◽  
Hard Rock ◽  
Task Force ◽  
Fractured Rock ◽  
Fracture Network ◽  
Atmospheric Conditions ◽  
Predictive Capability ◽  
Rock Laboratory ◽  
Modelling Methodology

AbstractThe Prototype Repository (PR) tunnel is located at the Äspö Hard Rock Laboratory near Oskarshamn in the southeast of Sweden. In the PR tunnel, six full-sized deposition holes (8.37 m deep and 1.75 m in diameter) have been constructed. Each deposition hole is designed to mimic the Swedish reference system for the disposal of nuclear fuel, KBS-3V. The PR experiment is designed to provide a full-scale simulation of the emplacement of heat-generating waste. There are three phases to the experiment: (1) the open tunnel phase following construction, where both the tunnel and deposition holes are open to atmospheric conditions; (2) the emplacement of canisters (containing heaters), backfill and seal in the first section of the tunnel; and (3) the emplacement of canisters, backfill and seal in the second section of the tunnel. This work describes the numerical modelling, performed as part of the engineered barrier systems (EBS) Task Force, to understand the thermo-hydraulic (TH) evolution of the PR experiment and to provide a better understanding of the interaction between the fractured rock and bentonite surrounding the canister at the scale of a single deposition tunnel. A coupled integrated TH model for predicting the wetting and the temperature of bentonite emplaced in fractured rock was developed, accounting for the heterogeneity of the fractured rock. In this model, geometrical uncertainties of fracture locations are modelled by using several stochastic realizations of the fracture network. The modelling methodology utilized information available at early stages of site characterization and included site statistics for fracture occurrence and properties, as well as proposed installation properties of the bentonite. The adopted approach provides an evaluation of the predictive capability of models, it gives an insight of the uncertainties to data and demonstrates that a simplified equivalent homogeneous description of the fractured host rock is insufficient to represent the bentonite resaturation.

scholarly journals Siderophore Production by Pseudomonas stutzeri under Aerobic and Anaerobic Conditions

2007 ◽  
Vol 73 (18) ◽  
pp. 5857-5864 ◽  
Author(s):  
Sofia A. Essén ◽  
Anna Johnsson ◽  
Dan Bylund ◽  
Karsten Pedersen ◽  
Ulla S. Lundström
Keyword(s):  
Mass Spectrometry ◽  
Hard Rock ◽  
Bacterial Culture ◽  
Pseudomonas Stutzeri ◽  
Siderophore Production ◽  
Anaerobic Conditions ◽  
Rock Laboratory ◽  
Molecular Masses ◽  
Aerobic And Anaerobic ◽  
Aerobic And Anaerobic Conditions

ABSTRACT The siderophore production of the facultative anaerobe Pseudomonas stutzeri, strain CCUG 36651, grown under both aerobic and anaerobic conditions, was investigated by liquid chromatography and mass spectrometry. The bacterial strain has been isolated at a 626-m depth at the Äspö Hard Rock Laboratory, where experiments concerning the geological disposal of nuclear waste are performed. In bacterial culture extracts, the iron in the siderophore complexes was replaced by gallium to facilitate siderophore identification by mass spectrometry. P. stutzeri was shown to produce ferrioxamine E (nocardamine) as the main siderophore together with ferrioxamine G and two cyclic ferrioxamines having molecular masses 14 and 28 atomic mass units lower than that of ferrioxamine E, suggested to be ferrioxamine D2 and ferrioxamine X1, respectively. In contrast, no siderophores were observed from anaerobically grown P. stutzeri. None of the siderophores produced by aerobically grown P. stutzeri were found in anaerobic natural water samples from the Äspö Hard Rock Laboratory.

scholarly journals Permeability Enhancement and Fracture Development of Hydraulic In Situ Experiments in the Äspö Hard Rock Laboratory, Sweden

2018 ◽  
Vol 52 (2) ◽  
pp. 495-515 ◽  
Author(s):  
Günter Zimmermann ◽  
Arno Zang ◽  
Ove Stephansson ◽  
Gerd Klee ◽  
Hana Semiková
Keyword(s):  
Hard Rock ◽  
Permeability Enhancement ◽  
Rock Laboratory ◽  
Fracture Development ◽  
In Situ Experiments

A geoscientific site descriptive model for the Äspö Hard Rock Laboratory, SE Sweden

2021 ◽  
Author(s):  
Jesper Petersson ◽  
Peter Hultgren ◽  
Mansueto Morosini ◽  
Frédéric Mathurin
Keyword(s):  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
Hard Rock ◽  
Saline Water ◽  
Regional Scale ◽  
Building Blocks ◽  
Special Focus ◽  
Low Grade ◽  
Descriptive Model ◽  
Rock Laboratory

<p>The development of an updated geoscientific site descriptive model (SDM) is currently in progress for the Äspö Hard Rock Laboratory (Äspö HRL), the key underground research facility of the Swedish Nuclear Fuel and Waste Management Company (SKB). Äspö HRL is located in south-eastern Sweden, within a suite of 1.81–1.76 Ga granitoids, and consists of a tunnel system down to 460 m depth with a total length of about 5 km. Tectonically, the area is part of a contractional shear belt, primarily manifested by a NE-SW trending regional deformation zone, which partly transect the underground facility. The shear zone system has evolved gradually over a prolonged period, with an initial low-grade ductile development, followed by multiple events of brittle reactivation. The structural framework is characterised by a significant heterogeneity in the hydraulic flow properties, where the most transmissive structures belong to a set of less extensive, conjugate zones and fractures.</p><p>More than 30 years of studies, starting with the pre-investigations and construction of the facility, have generated a wealth of geoscientific data in 3-D space, and hence a sound basis for an update of existing models. The SDM under current development aims to present an integrated geoscientific understanding of the Äspö site, with special focus on geology, hydrogeology and hydrogeochemistry. The general working procedure includes basically an initial stage of data capture, followed by an intermediate interpretative stage, and finally the construction of 3-D models with associated concepts and parameters. An explicit goal throughout the work has been to encourage interaction between the different geo-disciplines, especially during the interpretative stage, as a forerunner to the final stage of deterministic/conceptual modelling. During the interpretative stage, geological and geophysical information were combined into two basic building blocks along individual boreholes, tunnels, and outcrops: rock units and possible deformation zones, which were assigned hydraulic parameters such as primarily K-values. The subsequent geological 3-D modelling comprises two components: rock domains and deformation zones with a surface trace length of ≥ 300 m. Hydrogeological feedback was provided in terms of K-anisotropies and depth trends.</p><p>The fundamental outcome of the modelling is a more profound conceptual understanding, along with geometries and properties for each domain or zone. Additional outcomes are data on and understanding of the effects of 25 years of artificial tunnel drainage on groundwater pressures, flow and chemistry. The natural groundwater system, originally formed by paleoclimatic and geological factors over a vast period, has be profoundly influenced by important monitored phenomena. Upflow of deep-lying saline water and extensive intrusion of current seawater disclose the apparent hydro-properties and interconnection between deformation zones.</p><p>Currently, geological 3-D model includes geometries for ten rock domains and 24 deformation zones, the latter with seamless transitions to zones of the regional scale Laxemar model, as developed by the SKB with the objective of siting a geological repository for spent nuclear fuel in the proximity to the Äspö HRL. As completed, the models will serve as framework for more detailed-scaled facility models.</p>

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