| 1. |
- Fransson, Åsa, 1971, et al.
(författare)
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Characterization of fractured crystalline rock: two Swedish in situ field experiments
- 2014
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Ingår i: 1st International Discrete Fracture Network Engineering Conference, 20-22 oct 2014, Vancouver, Canada.
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Konferensbidrag (refereegranskat)abstract
- Construction of a nuclear waste repository requires information and an understanding of the fractured rock. The Swedish concept for nuclear waste deposition that is currently being developed by the Swedish Nuclear Fuel and Waste Management Co (SKB) includes a natural barrier in the form of crystalline rock, and engineered barriers in the form of bentonite and a copper canister. This paper aims to present two in situ field experiments: the first is the Large fractures experiment and the second is BRIE, the Bentonite Rock Interaction Experiment. Important issues include possible deformation (shearing) of fractures and deformation zones influencing the localization of canisters, and fluid flow, resulting in hydration of the bentonite. The aim of Large fractures is to further develop strategies and integrated investigation and modelling methodology for the identification and characterization of geological structures to ensure that (size) determination of large fractures or minor deformation zones to a greater extent can be based on real properties and to a lesser degree on a criterion related to the existence of a full perimeter fracture – tunnel intersection. BRIE is a field experiment which addresses the hydraulic interaction between the system components of compacted bentonite and the near-field host rock composed of hard and fractured bedrock. The above experiments are presented in terms of investigations performed to obtain discrete fracture descriptions. Grouting of fractures intersecting the investigation borehole of the Large fractures experiment was designed based on field data and a decrease in flow from above 200 liters/min to below 1 liter/min was achieved. The magnitude of the transmissivity of the fracture/deformation zone that was grouted indicates a large fracture size. This is also indicated by the ongoing integrated interpretation (geology, hydrogeology and geophysics). Results from BRIE show that hydration is uneven and is controlled by the main conductive fracture, highlighting the need for a relevant fracture description.
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| 2. |
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| 3. |
- Fransson, Åsa, 1971, et al.
(författare)
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Swedish grouting design: hydraulic testing and grout selection
- 2016
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Ingår i: Ground Improvement. - : Thomas Telford Ltd.. - 1365-781X. ; :4, s. 275-285
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Tidskriftsartikel (refereegranskat)abstract
- © 2016, Thomas Telford Services Ltd. All rights reserved. To ensure successful sealing of rock and soil, an adequate description of the system to be grouted is required as a basis for the grouting design and the selection of the grouting material. In rock, the individual fractures and the hydraulic apertures of these fractures form the basis of the Swedish grouting design concept. The hydraulic aperture is a key parameter when describing grouting behaviour and it is used to determine the extent to which the grout can enter fractures - that is, the penetrability. The hydraulic aperture also determines the penetration length, and therefore the grout parameters (e.g. yield stress and viscosity) as well as the grouting pressure and time needed to be adopted to the hydraulic aperture. Once these parameters are chosen, a suitable grouting technique can be adopted. Simple, practical rock and grout tests are important inputs to ensure correct design and performance. The aim of this paper is to present a testing procedure and provide examples from laboratory and field experience to demonstrate that the approach also works in practice.
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| 4. |
- Funehag, Johan, 1975, et al.
(författare)
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Grundläggande egenskaper för injektering och inträngning av bruk
- 2014
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Ingår i: Bergmekanikdag 2014, Stockholm.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Injektering i hårt berg inkluderar vetenskaper som flöde av vätskor, reologi, hydrogeologi, material kännedom, geologi och annat. Att faktiskt förstå och ha en känsla för hur flöde fungerar i sprickor är viktigt. Detta kan lätt glömmas av och energi läggs allt som oftast på andra delar exempelvis på materialetkunskap. Denna artikel syftar till att beskriva hur flöde sker i sprickor och bör kunna bidra till en känsla av hur flödet av bruk faktiskt sker. Artikeln utgår från framtagna samband för spridning baserat på Binghamflöden för att beskriva hur yttre händelser som kan uppträda vid vanlig injektering kan påverka spridningen. En verifikation av inträngningslängder i en nyligen tillverkad sprickmodell används för att visa hur ett Binghamflöde beter sig. Både spridning och hur ett sambandshål påverkar spridningen visas samt hur detta kan påverka designkriterier. Filmvisning av injekteringsflöde i sprickrepliken kommer säkerligen bringa lite mer klarhet i hur teoretiska beräkningar kan användas som modeller.
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| 5. |
- Funehag, Johan, 1975, et al.
(författare)
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Radial penetration of cementitious grout - Laboratory verification of grout spread in a fracture model
- 2018
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798. ; 72, s. 228-232
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Tidskriftsartikel (refereegranskat)abstract
- During the past two decades of research and development in the field of grouting in hard jointed rock, the design process has taken a number of significant leaps forward. A grouting design in hard rock can now be based on the penetration length of grout in individual rock fractures. For cementitious grouts, the most common rheological model used is the one for a Bingham fluid. The model is a conceptualisation of grout spread where two rheological properties of the grout viscosity and yield stress govern the penetration length along with the fracture aperture and applied grouting overpressure. This paper focuses on verification of radial Bingham flow of cementitious grout using a fracture model constructed from acrylic glass. Each test conducted using the fracture model was filmed, allowing the grout spread to be analysed as penetration length over time. The measured penetration lengths were then compared with analytical solutions derived for Bingham grout in a plane parallel fracture. The results indicate that the penetration of cementitious grout in fracture apertures of 125 gm and 200 gm is verified for up to 40% of the maximum possible penetration length. This can be compared to normal grouting, where the penetration lengths achieved are around 20% of the maximum penetration length.
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| 6. |
- Runslätt, Edward, 1984, et al.
(författare)
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Statistical Evaluation of Groutability Using Data from Hydraulic Tests and Fracture Mapping Case Studies from Sweden
- 2017
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Ingår i: Geotechnical Special Publication. - Reston, VA : American Society of Civil Engineers. - 0895-0563. ; :288, s. 185-195
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Konferensbidrag (refereegranskat)abstract
- Sweden has a long history of research within the field of rock fissure grouting in hard crystalline rock mass due to strict environmental requirements regarding allowable ground water draw down. These requirements normally implies that fractures down to aperture size between 50 to 100 μm needs to be sealed and within these ranges the size of the particles for cementitious grouting agents becomes a limiting factor. For a grouting design it is therefore of importance to consider the aperture size distribution of the rock mass in order to predict the groutability for both cementitious and non-cementitious grouting agents. Transmissivity data from hydraulic tests (water pressure tests) and number of fractures along a borehole can be assessed from core logging for further use as input for a statistical interpretation of fracture data to simulate an aperture size distribution. A methodology developed at Chalmers University of Technology in Gothenburg, Sweden, is proposed. The method is a statistical evaluation of groutability (SEG) and is based on the Pareto distribution. A computational design tool has been developed to simplify the use of the statistical evaluation and to make the research more accessible to end users, designers, in the grouting industry. The aim of this article is to present two case studies where the statistical interpretation of fracture data is performed by using the computational design tool and how the outcome can be of great use in finding a more accurate grouting design. The case studies include fracture data sets from two large infrastructure rock tunnel projects in Sweden; a road tunnel in Stockholm and a railroad tunnel in Gothenburg.
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| 7. |
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| 8. |
- Thörn, Johan, 1986, et al.
(författare)
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Calculation tool for hydraulic characterization during grouting design
- 2016
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Ingår i: 8th Nordic Grouting Symposium. - 9788282080507 ; , s. 28-40
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Konferensbidrag (refereegranskat)abstract
- An understanding of the fracture aperture distribution facilitates design of grouting measures in crystalline rock masses, this since both the penetrability (ability of grout to enter the fractures) and penetration length is linked to the aperture. This is considered in a design process for rock grouting that has been developed at Chalmers University of Technology. The process suggests that fracture aperture distribution can be estimated based on transmissivity data from hydraulic tests combined with fracture data from boreholes. However, hydraulic tests seldom contain information that can be linked to individual fractures and measurement data need to be further processed using probability distributions. To resemble a rock mass where few fractures dominate the flow Fransson suggested the use of a Pareto distribution and combinatorics to estimate transmissivity of individual fractures. A freely available computational tool for the statistical analyses based on this concept with Pareto distributed fractures was developed previously. The purpose of the tool is to process field data and create probability distributions that can be used as input to grouting design and approximate tunnel leakage estimates. The methodology has been developed with tunnel data, which sofar has been the main application. For dam and open cut grouting, with higher proportions of surficial rock the validity of the connectivity assumptions may need to be investigated. This paper briefly present the design process and calculation tool in its context using real datasets from a Swedish tunneling project, to provide advice on usage and to give examples of pitfalls in data collection.
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| 9. |
- Thörn, Johan, 1986, et al.
(författare)
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Fracture Deformation Measurements during Grouting in Hard Rock
- 2012
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Ingår i: Geotechnical Special Publication. - Reston, VA : American Society of Civil Engineers. - 0895-0563. - 9780784412350 ; :228 GSP, s. 836-845
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Konferensbidrag (refereegranskat)abstract
- When a fracture system in crystalline rock is grouted the rock mass may deform. Such deformations may reduce the grouting efficiency since new flow paths are opened. The work presented here show that deformations occur at hydraulic tests and grouting and that deformation can be measured and evaluated as stiffness from in situ tests. Deformation measurements, hydraulic testing, and grouting was conducted in spring 2010 in the Hallandsås tunnel and hydraulic testing in a service tunnel in Gothenburg (Runslätt and Thörn, 2010). For measuring physical deformation recently developed equipment from Chalmers University of Technology was used. Deformations were measured seven times in the same borehole. Three measurements were during grouting, and the remaining four from water pressure tests. Most deformations occurred at pump pressures of 1-1.4 MPa, which is lower than the calculated normal rock stress. Stiffness has been evaluated in several ways, including a new method, (Fransson, et al., 2010). Generally the evaluated stiffness is lower in the Hallandsås tunnel than in the Gothenburg tunnel. The results show agreement with other in situ experiments.
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| 10. |
- Fransson, Åsa, 1971, et al.
(författare)
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Hydromechanical characterization of fractures close to a tunnel opening: A case study
- 2012
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Ingår i: ISRM International Symposium - EUROCK 2012.
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Konferensbidrag (refereegranskat)abstract
- Important factors influencing the hydromechanical behavior of a fracture are in situ rock stresses (natural and induced) as well as hydraulic heads, fracture orientation, connectivity and fracture geometry, including their infillings. Particular attention is given to larger, water-conducting fractures that intersect or are close to a tunnel. For the Bentonite Rock Interaction Experiment (BRIE) at the Äspö Hard Rock Laboratory (HRL) in Sweden, the interaction between rock and bentonite in a deposition borehole is of particular interest. The BRIE experiment is being conducted at a depth of 420 meters in crystalline rock. This paper presents results from the initial identification, characterization and modeling of a small number of fractures close to the tunnel opening. So far, these fractures have been identified as the most important water-conducting fractures. In this identification and characterization exercise, core-drilled, vertical, three-meter deep investigation boreholes were made in the tunnel floor. Logging of natural hydraulic heads in boreholes and hydraulic tests, along with borehole and tunnel mapping in combination with modeling, indicate small deformations. This was also confirmed by deformation measurements performed in the boreholes. The description of the site will be further updated and revised and additional investigations into the link between stress history, fracture geometry and selection of fracture mechanical properties will be of particular interest.
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