| 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. |
- 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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| 3. |
- 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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| 4. |
- Funehag, Johan, 1975, et al.
(författare)
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How the Pressure Build-Up Affects the Penetration Length of Grout-New Formulation of Radial Flow of Grout Incorporating Variable Pressure
- 2017
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Ingår i: Geotechnical Special Publication. - Reston, VA : American Society of Civil Engineers. - 0895-0563. - 9780784480793 ; :288, s. 143-151
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Konferensbidrag (refereegranskat)abstract
- For around two decades of research and development in the field of grouting in hard jointed rock, the design process has taken some leaps forward. Stille and Gustafson, 2005 and Funehag and Gustafson 2008, shows how a grouting design can be computed. A grouting design in hard rock can based on the penetration length of grout in rock fractures. The design comprises considerations of the fracture apertures in the rock mass, the type of grout and its rheological properties and how the grout is injected i.e pressure and grouting times. When knowing these parameters an optimized geometry fitting the design is made. Thörn, et al, 2014 describes a fundamental analysis with a comprehensive tool to retrieve the fracture distribution and aperture distribution of the fractures crossing a cored borehole. The data needed about the core is geological mapping and hydraulic section tests. In Gustafson, Claesson and Fransson, (2013) a full derivation of a radial Bingham flow in a slit is described for constant pressure. By optimizing with a specific pressure and an efficient grouting time (efficient time means the time when the pressure has reached the designed pressure) a prognosis a more realistic time consumption for grouting can be computed. However, the time it takes to reach a certain pressure is dependent on the capacity of the pump and the how large the fractures widths are. For poorly chosen pumps together with large fractures the time to reach the design pressure can be significant. The overall objective for this new formulation was to involve the grouting pressure as a variable rather than constant. A pressure build-up mimic more a realistic pumping scenario which enables better prognosis of grouting works. This paper brings up this new formulation of the radial Bingham flow with variable injection pressure in slit. The benefits of this new formulation is that it can easily be integrated in other computer programs. One program that uses this new formulation is a grouting simulator owned and developed by Edvirt AB. The simulator has been used to pedagogically demonstrate how a variable pressure and restrictions in grout flow (the pump capacity) affect the penetration length. Further, the results show that it can be used to predict suitable pump capacity to fit the coming grouting works.
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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. |
- 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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| 7. |
- Andersson, Patrik, 1974, et al.
(författare)
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Framtidsbilder för samhällsbyggnad
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Framtidsbilder för samhällsbyggnad 2020De kommande 15 åren står institutionen för Bygg- och miljöteknik inför stora förändringar. Därför har institutionen initierat projektet Framtidsbilder 2020 där man engagerat en framtidspanel bestående av elva yngre disputerade forskare. Arbetet inleddes med ett breddgruppsmöte där 110 personer representerande institutionens personal och studenter deltog. Vid mötet identifierades ett antal trender och osäkra utvecklingar som påverkar framtiden inom samhällsbyggnadsområdet. Deltagarna bidrog också med idéer till en önskvärd utveckling, vilket har sammanställts och utgör grunden till en gemensam önskvärd framtid/vision för institutionen. Materialet från breddgruppsmötet har bearbetats av Framtidspanelen och resulterat i fyra scenarier som beskriver hur samhällsbyggnadsområdet kan se ut år 2020. Syftet med framtidsbilderna är att de ska vara vägledande för institutionens beslut och förhållningssätt under de kommande åren.Fyra scenarierTurning TorsoSamhället präglas av en ekonomi som är på uppgång, och av ett nytänkande och öppet samhälle. Materiell status och individualism är viktigt. Detta leder till en hög arbetsbelastning samt krav på exklusiva varor av hög kvali-tet. Det finns en stor medvetenhet om miljöpåverkan och klimatförändringar och lösningarna för att klara energiförsörjningen är innovativa.Eco-metropolenDet sveper en grön våg genom dagens samhälle. Under de senaste 15 åren har vi insett att jorden skall vara en bebolig plats även åt dem som kommer efter oss. Vi söker ständigt efter nya, mer förfinade metoder att tillvarata de resurser vi har. Samhället och individen är i balans. Ekonomin är god och vi är miljömedvetna, trygga och integrerade. Nytänkande premieras och icke- materialistiska värderingar står högt i kurs. Vi tänker individuellt, men agerar mer än gärna för kollektivets bästa. Utbildning är gratis TrädgårdsstadenEtt samhälle där vi lärt oss hantera stress, men känner oss otrygga och helst umgås i slutna sociala sammanhang. Vi bor enkelt inne i stan, eller gärna på landsbygden nära storstäderna. Minskade behov av högutbildade i samhället gör att vi har svårt att rekrytera studenter till teknikutbildningar. Det traditionella tankesättet leder till kulturkrockar med företag och personer från andra länder.Gated communitiesFörsämrad ekonomi och ökad egoism har lett fram till ett stressat, otryggt och segregerat samhälle. Accelererande klimatförändringar och ökad miljö-påverkan skrämmer oss, men trots det åtgärdar vi inte problemen, utan koncentrerar oss på konsekvenserna. Arbetslöshet i samhällsbyggnadssek-torn leder till sänkt status för samhällsbyggaren. Vi har därför svårt att rekrytera studenter, och även forskningen har låg status.
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| 8. |
- Axelsson, Magnus, 1974, et al.
(författare)
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Design criteria for permeation grouting in hard rock at great depths
- 2008
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Ingår i: Proceedings World Tunnel Congress 2008, Underground facilities for better environmnet and saftey. ; 1, s. 510-520
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Tidskriftsartikel (refereegranskat)abstract
- Grouting at tunnelling in hard rock at great depths below the groundwater table, when constructing a nuclear waste repository for example, makes special demands on the strength of the grout in order to resist groundwater forces. The aim of this study is to distinguish the most important parameters to ensure that suitable grouting can be performed at large depths. Initially, laboratory studies were conducted in order to determine the most critical parameters. The results from the laboratory tests were used in a field study at the Äspö Hard Rock Laboratory in Sweden. The results indicate that the most important characteristics for the rock are the fracture aperture and the groundwater gradient and for the grout: a resolute grouting pressure and sufficient early strength. This implies that for cementitious grouts the yield stress is important and for non-cementitious grouts it is the shear strength prior to gelling. The results emphasise the need to perform hydraulic characterisation of the rock mass in advance. The results also show the importance of performing a proper grouting, especially at large depths where a decreased penetration length of the grout increases the risk of a high gradient and hence erosion of the grout.
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| 9. |
- Butron, Christian, 1978, et al.
(författare)
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A Swedish grouting design concept: Grouting with silica sol in the Nygård and Törnskog tunnels
- 2012
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Ingår i: Geotechnical Special Publication. - Reston, VA : American Society of Civil Engineers. - 0895-0563. - 9780784412350 ; :228 GSP, s. 826-835
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Konferensbidrag (refereegranskat)abstract
- The scope of this paper is to present two tunnel grouting design case studies where the waterproofing aimed not only to reduce the water inflow to a specified level, but to minimize the number of dripping spots by means of pre-excavation grouting. Every grouted section of around one hundred meters in both tunnels used relevant parameters from the rock and the grout material properties to develop an adequate, pre-excavation grouting design. Both tunnels, constructed in crystalline rock, used silica sol as the main grouting material and were evaluated later by means of control boreholes and dripping characterization. Control boreholes showed a decrease in the transmissivity in these sections, and the dripping characterization showed a reduction in the number of dripping spots compared to the rest of the tunnel, where this pre-excavation grouting concept was not used. This led to minimization of the number of drains used, which was clearly visible in the Nygård case, suggesting that the designs were successful and confirming that an understanding of the rock and grout properties is crucial to the design concept.
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| 10. |
- Butron, Christian, 1978, et al.
(författare)
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Assessment of the transmissivity field in fractured rock: A case study in the tass tunnel
- 2009
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Ingår i: Nordic Symposium of Rock Grouting.
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Konferensbidrag (refereegranskat)abstract
- Water Pressure Tests (WPTs) among other hydraulic tests were conducted in each borehole before and after the pre-excavation grouting of a test tunnel in the Äspö HRL (Hard Rock Laboratory) built in 2008 and 2009 “the TASS tunnel”. This paper shows how data from WPTs can give information on the connectivity and asses the transmissivity fields of fractured rock. The results showed that the connectivity range of the rock before grouting is approximately 3 m, which seems to be a common range in crystalline fractured rocks. Results clearly indicate that the most conductive parts of each fan were where the grout has penetrated the most during grouting. They also show that the reduction of the transmissivity in the rock by means of grouting is about four orders of magnitude within the studied rock volume of a fan. This sealing takes place easily on planar fractures where the transmissivity is high (a few conductive fractures that give the major contribution to the borehole transmissivity) and what is left unsealed is a highly channelized system. This channelized system will be extremely difficult to hit by future boreholes, which will make post-grouting a very complex task.
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| 11. |
- Butron, Christian, 1978, et al.
(författare)
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Drip sealing of tunnels in hard rock: A new concept for the design and evaluation of permeation grouting
- 2010
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798. ; 25:2, s. 114-121
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new pre-excavation grouting concept to prevent dripping and reduce the inflow into a railway tunnel. For this purpose, the tunnel's roof was drip-sealed using colloidal silica and the walls and invert of the tunnel were grouted with cement. The grouting design process followed a structured approach with pre-investigations of core-drilled boreholes providing parameters for the layout. Water pressure tests and pressure volume time recordings were used for the evaluation. Results showed that the design was successful: the total transmissivity was reduced from 4.9 x 10(-08) m(2)/s to the measurement limit (1.6 x 10(-08) m(2)/s), and the dripping was reduced to eight spots from the roof. Improved rock characterisation showed that the grout hole separation was within the transmissivity correlation length and that grouting efficiency depends to a large extent on the dimensionality of the flow system of the rock mass. (c) 2009 Elsevier Ltd. All rights reserved.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Fransson, Åsa, 1971, et al.
(författare)
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A swedish grouting design concept: Hydraulic testing and selection of grout
- 2012
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Ingår i: Geotechnical Special Publication. - Reston, VA : American Society of Civil Engineers. - 0895-0563. - 9780784412350 ; :228 GSP, s. 1691-1700
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Konferensbidrag (refereegranskat)abstract
- Some grouting boreholes take no grout and some boreholes take too much, two extremes related to grouting technique, grout properties and the properties of fractures intersecting the boreholes. Successful sealing of rock and soil demands an adequate description of the system to be grouted as a basis for grouting design and selection of grouting material. The basis for this Swedish concept of grouting design is the individual fractures and the hydraulic apertures, b, of these fractures. The hydraulic aperture is an important parameter to describe the grouting behavior and is used to determine if the grout can enter the fractures, the penetrability. The hydraulic aperture also determines the penetration length in addition to grout parameters e.g. yield stress, τ0, and viscosity, μg as well as grouting pressure and time. Knowing these parameters, a proper grouting technique can be adapted. Important input for both design and performance are simple and practical tests of rock and grout and the intention of this paper is to present a testing procedure and give examples from laboratory and field experiences that the approach actually works. © 2012 American Society of Civil Engineers.
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| 17. |
- Funehag, Johan, 1975
(författare)
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Grouting and Analyses of a Fracture in Äspö HRL, Characterisation, grouting and verification of grouting results for silica sol
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report is part of the project Non-cementitious low-pH injection grout for smaller fractures that is a sub-project under the main project Injection grout for deep repositories. The project is financed by SKB (Sweden), Posiva (Finland) and NUMO (Japan). The sub-project objective is to find a grout that can be used to grout fractures with a hydraulic aperture less than 100 μm and that fulfills environmental and long-term safety demands.This report describes a field test conducted during spring 2004 in a pillar located in the main tunnel at Äspö HRL at a depth of around 100 m below the surface. Previous studies (Fransson, 2001) show that the fracture of interest is found in a section 2.0-2.5 m in a borehole drilled parallel to the main tunnel. The transmissivity is around 5x10-8 m2/s corresponding to a hydraulic aperture of approximately 40 50 μm. The fracture has earlier been grouted with cement which resulted in a penetration length of around 0.1 m around the grouted borehole (Eriksson, 2002).The fracture was grouted with a silica sol, produced by Eka Chemicals, Bohus under the name Eka® Gel EXP36. It consists of extremely small amorphous silica particles suspended in water. The accelerator used was a salt solution, CaCl2 (2,9%). The pH is around 10. The grout was also mixed with optical brightener to make it possible to see the grout using UV-light. The grouting design was determined using the hydraulic aperture analysed by Fransson, 2001. Three methods were used to determine the penetration length and sealing efficiency; namely detection of grout in 6 cores using UV-light, analysing part of the grouted fracture in microscope and using hydraulic tests. The results show that five of totally six cores had traces of silica sol, which would indicate a penetration length of at least 1 m in the fracture. The microscopy analyses verify that silica sol were apparent in the fracture but not completely filled. The achieved penetration length of 1 m was compared with 2-D mathematical model. The results show that the model underestimates the penetration length with 0.25 to 0.35 m. The hydraulic tests result in a sealing efficiency of the silica sol grouting in the affected rock mass of 70%.
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| 18. |
- Funehag, Johan, 1975
(författare)
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Grouting of Fractured Rock with Silica Sol; Grouting design based on penetration length
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- ABSTRACTRecent grouting projects in Sweden have concentrated on the grout itself. The only grout normally used in Sweden is cement-based. During the past 10 years, the acceptable flow of water into tunnels has been reduced significantly. The current requirements mean that an average fracture aperture of around 0.05 mm must be sealed. Chemical grouts generally have a low initial viscosity and the absence of particles means that they can penetrate narrow fractures. Recently, the environmental impact of non-cement grouts has become an important issue. Silica sol is a material that seems to fulfil both requirements, as it is non-hazardous and capable of penetrating narrow fractures.The main objectives of this study are to investigate the basic concepts of how rheology affects penetration and to develop models for calculating penetration length. Other aims are to analyse the need for sealing narrow fractures and to find out how the grouting design can be linked to the characterisation of the rock mass. The papers deal with the grouting procedure with silica sol and analyse a concept for evaluating sealing efficiency and penetration length. In two laboratory studies conducted in a sand-column and pipes, parameters affecting the penetration length were studied. In both studies the aim was to equate the penetration length of the sand and in pipes with that in a slit. For the pipe, the equivalent aperture involves only the radius of the pipe and for the sand the aperture is proportional only to the porosity and calculated specific surface of the sand itself.The five papers outline the grouting procedure with silica sol and suggest a simple grouting model as well as a concept for evaluating the sealing efficiency and penetration length. The grouting design was based on the characterisation of the rock mass and the grouting parameters. A new design criterion for the grouting time was tested and evaluated to obtain a desired penetration length. The grouting time is strongly connected to the gel-time of the grout. The grout used was silica sol, a gelling liquid consisting of amorphous silica particles suspended in water. To initiate and accelerate the gelling process, salt solutions were used. Models were developed to calculate the grout penetration in both one and two dimensions. An interesting feature is that the penetration length calculated in 1-D is about twice as long as that for 2-D, which is verified partially by two field studies. The final penetration is the same as the penetration calculated using the analytical model with a grouting time equal to gel induction time, tG. Since the penetration models are based on the grout properties, the proposed calculations can be applied to most types of gelling liquids, provided the basics of the rheology are taken into account.
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| 19. |
- Funehag, Johan, 1975
(författare)
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Grouting of Hard Rock with Gelling Liquids, Field and Laboratory Studies of Silica sol
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recent grouting projects in Sweden have concentrated on the grout itself. The only grout normally used in Sweden is a cement-based one. During the past 10 years, the acceptable flow of water into tunnels has been significantly reduced. The current requirements mean that an average fracture aperture of around 0.05 mm has to be sealed. Chemical grouts generally have a low initial viscosity, and the absence of particles means that they can penetrate narrow fractures. Recently, the environmental impact of non-cement grouts has become an important issue. Silica sol is a material that seems to fulfil both requirements, as it is non-hazardous and capable of penetrating narrow fractures.The main objectives of this study are to investigate the basic concepts of how rheology affects penetration and to develop models for calculating penetration length. Other aims are to analyse the need for sealing of narrow fractures and to find out how the grouting design can be coupled to the characterisation of the rock mass. The three papers that make up this study deal with the sealing of narrow fractures in the field. The papers outline the grouting procedure with silica sol and analyse a concept for evaluating sealing efficiency and penetration length. In a laboratory experiment conducted with a sand column, the sand was characterised and the grout penetration was measured. The objective of this experiment was to equate the penetration length of the sand with that in a slit. The hydraulic aperture of a fracture in rock can be used to calculate penetration lengths; the equation derived for the equivalent aperture of the sand is proportional only to the porosity and calculated specific surface of the sand itself. The papers outline the grouting procedure with silica sol and test a concept for evaluating the sealing efficiency and penetration length. The grouting design was based on the characterisation of the rock mass and the grouting parameters. To obtain the desired penetration length, the correct mixing ratio and grouting pressure were determined. The grout used was silica sol, a gelling liquid consisting of amorphous silica particles suspended in water. To initiate and accelerate the gelling process, salt solutions were used. Models were developed to calculate the grout penetration, with dimensionless parameters, in both one and two dimensions. An interesting feature is that the penetration length calculated in 1-D is twice as long as that for 2-D, which is verified partially by two field studies. In the sand column test, the equivalent aperture of the sand is directly linked to the aperture of a fracture. In the second part of the test, the grout penetration stops long before the gel time of the grout is reached. The final penetration is the same as the penetration calculated by the analytical model with a grouting time equal to gel induction time, tG . Since the penetration models are based on the grout properties, the proposed calculations can be applied to most types of gelling liquids, provided the basics of the rheology are taken into account.
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| 20. |
- Funehag, Johan, 1975, et al.
(författare)
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Grouting with silica sol in the Törnskog Tunnel, Grouting design for silica sol in full production
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report describes a full-scale grouting test in the Törnskog Tunnel. The tunnel is part of the Nordlänken project north of Stockholm, which has two separated tunnel tubes. The test was conducted during production of the tunnel during spring 2005 in chainage from 12012 to 12112. A new concept of grouting was designed and executed based on the grouting material silica sol with the brand name Meyco MP320. Silica sol has been succesfully tested before in field tests in Hallandåsen 2003 and in Äspö HRL 2004. This test is the first test with silica sol in full production of a tunnel in hard rock. The initiative was taken by the National Road Administration, Oden Anläggningsentreprenad and AB BESAB. Design of the grouting procedure were based on a standard tests for characterisation of the rock mass. With use of a pareto-distribution curve, the hydraulic apertures of the fractures could be computed, further the hydraulic apertures was used to estimate the inflows to the tunnel. The demands set on the allowable leakage into the tunnel resulted that hydraulic apertures down to 14 μm needed to be sealed. Cement can penetrate and seal apertures down to 0.05 - 0.1 mm and therefore it was necessary to use a grout material that has a better penetrability, like silica sol. The grout, named Meyco MP320, was chosen and the design parameters were established: grout pressure, gel time, grouting time. The desired penetration was 1.2 m in order to limit unnecessary spread of the grout. The design was different than the traditional grouting methods with demands set on the effective grouting time at a prescribed pressure. All grout fans were carefully monitored using hydraulic tests, before and after grouting as well as control of the actual grouting. Last, the result of the grouting was complemented with a drip characterisation. Two types of grout fans were used. One with the above mentioned grout procedure and one based on the grouting procedure normally used in the Törnskogs Tunnel, but with silica sol instead of cement. The first type fan was used when the rock quality was poor. The other when the rock quality was better. The test with these type fans with silica sol were conducted in one tunnel tube, T201, the other tube was grouted with cement following the standard procedure used in the project. This enabled a comparison of the sealing effect between the cement grouted tunnel tube and silica sol grouted tube.The results of the grouting showed that 8 out of totally 9 grouting fans were successful. The designed fans were used in five cases were the rock mass were presumed to be of poor quality, that is with larger fracture zones present. The objective for this field test was to limit the inflow of water to tunnel corresponding to value of the transmissivity of 3.2ּ10-7 m2/s for the grouted section of 100 m. After grouting the achieved transmissivity was calculated to be 6.2ּ10-7 m2/s. The achieved value of the transmissivity is rather close to the desired; the achieved value considers all fans, including the unsuccessful one. No significant conclusion could be made with the comparison of the sealing effect using cement or silica sol as a grouting agent. The conclusion is that the technique of grouting is very important and more effort needs to be done regarding the grouting time.
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| 21. |
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| 22. |
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| 23. |
- Funehag, Johan, 1975, et al.
(författare)
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New frontier in post-grouting of tunnels 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. 846-856
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Konferensbidrag (refereegranskat)abstract
- Post-grouting is a difficult task. It is often coupled with high costs and a result that is difficult to quantify. An infrastructure tunnel in an urban city in southern Sweden was used to develop and implement design methodology for post-grouting. The water inflow measured in weirs prior to post-grouting was about 3.8 l/min/100 m. The task of sealing low water inflows to achieve even lower ones takes a lot of effort and determination. The tunnel was built in the 1970s using the traditional drill-and blast method. During the pre-investigations of the project the analysis showed very good pre-grouting, giving a sealed zone of almost 10 meters. The tunnel had a large, sealed zone with a smaller hydraulic gradient and only narrow fractures were left unsealed. The grout chosen was the newly developed silica sol for the presumed narrow fractures and a robust cement grout if large inflows were hit by the grout holes. The tunnel is small, roughly 12 m2 and heavily congested with cables and heating pipes, making it difficult to use traditional machinery. The tunnel section, 90 m in length, was divided into three different sub-sections, each with specific goals. The result showed that the strategy developed worked well and production was more rapid than presumed. The targeted water inflow rate of 1 l/min was met. © 2012 American Society of Civil Engineers.
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| 24. |
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| 25. |
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| 26. |
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| 27. |
- Grøv, E., et al.
(författare)
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Rock mass grouting in Sweden and Norway A matter of cultural differences or factual causes?
- 2014
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Ingår i: Geotechnical News. - 0823-650X. ; 32:1, s. 41-51
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Tidskriftsartikel (refereegranskat)abstract
- There are some distinct differences between the practices of rock mass grouting in Sweden and Norway. The Swedish approach is to a large extent theoretically based, whereas, the Norwegian approach is to a large extent empirical based. The Norwegian approach was developed during extensive tunneling for hydroelectric power development in a context where the practical aspects governed the grouting and then it moved to urban tunnels. The Swedish approach has been directly applied in urban tunneling and lots of experience on extreme tight requirements from the underground storage of radioactive waste has been included. The Norwegian approach is based on close cooperation at the tunnel face and customizing the works according to the encountered conditions. The Norwegian approach is synonymous with high pressure grouting. The Swedish approach applies low to moderate grout pressure. The Swedish approach uses contract type based on the amount invested.
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| 28. |
- Gustafson, Gunnar, 1945, et al.
(författare)
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Design of grouting with silica sol in hard rock - New design criteria tested in the field, Part II
- 2007
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Ingår i: Tunnelling and Underground Space Technology. - 0886-7798. ; 23 (2008):1, s. 9-17
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Tidskriftsartikel (refereegranskat)abstract
- An extensive field test was conducted in spring 2005 in the Törnskog Tunnel and consisted of design, execution and evaluation of a grouting campaign for 100 m of tunnel. The field test was part of the normal construction of the tunnel. This paper describes how the design of the grouting was coupled with the actual grouting procedure. A preliminary investigation of the tunnel showed that the location where this field test was conducted had a large fracture zone. A drill-core was taken in this zone and hydraulic tests were performed. From the evaluation of the rock core a fracture aperture distribution was assessed and the grouting design was focused on this part of the tunnel. The evaluation showed that apertures down to 14 μm needed to be sealed to cope with stipulations set for leakage into the tunnel (2 l/min and 100 m of tunnel). A design was made based on silica sol, where a critical penetration length was decided and the layout of the grouting fan could be determined. A new design was chosen, with a specific pumping time of 30 min at a grouting pressure of 1.1 MPa. The design worked well and the water ingress was reduced. A drip characterisation in both tunnel tubes was made. One tube was grouted with silica sol and the other with cement following a more traditional approach. The drips were both larger and more frequent in the cement-grouted tube than in the silica sol-grouted tunnel. Eight out of nine fans grouted with silica sol showed a significant sealing effect. For one fan the design was not followed. Instead, the workers used the more traditional method, i.e. only pumping until the design pressure was reached, which produced a poor result. This paper demonstrates the efficiency of design methodology that takes into account the hydraulic apertures and that the required minimum penetration length can be coupled to the apertures when formulating the grouting criteria.
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| 29. |
- Gustafson, Gunnar, 1945, et al.
(författare)
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Design of grouting with silica sol in hard rock - New methods for calculation of penetration length, Part I
- 2007
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Ingår i: Tunnelling and Underground Space Technology. - 0886-7798. ; 23 (2008):1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- To meet the demands laid down for recent tunnel projects in Sweden, a great deal of effort has been devoted to the grouting materials. Silica sol is a grouting material that penetrates and seals fractures where cement cannot. Studies show that in rheological terms, silica sol works differently compared with cementitious grouts and in the literature there is a lack of models to calculate the penetration lengths. In recent times there has been an increase in the use of silica sol, in major tunnel projects for example, and there is a need to understand the basics regarding its penetration in order to gain a better understanding of what can be accomplished. The fundamental difference between a gelling liquid and a cementitious grout is that initially the gelling liquid acts in the same way as a Newtonian liquid. It thus has no yield shear strength and it will continue to flow as long as there is a pressure gradient. The cementitious grout acts like a Bingham fluid, with a yield shear strength to which the penetration length can be linked. Several authors have described how the rheological models can be used to calculate the penetration length of grouts. Part I of this paper deals with how the penetration length can be computed analytically, both as 1-D channel flow and 2-D radial flow. At the end of this paper a simple rule of thumb is suggested where the penetration length is easily computed using knowledge of the hydraulic aperture and the pressure and only involving the initial viscosity of the grout and the gel induction time.In part II it is shown how the analytical models can be used to design grouting in hard rock. It also shows how the theoretical expressions are transformed into practical design criteria for grouting.
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| 30. |
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| 31. |
- Hernqvist, Lisa, 1968, et al.
(författare)
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A hard rock tunnel case study: Characterization of the water-bearing fracture system for tunnel grouting
- 2012
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798. ; 30, s. 132-144
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Tidskriftsartikel (refereegranskat)abstract
- Grouting is a common method for reducing water inflow in tunneling projects in hard rock. A good grouting design should be adapted to the water-bearing fracture system in the rock mass. The aim of this work is to present a case study using relevant parameters, to suggest a combination of tests to provide them, and to show how a conceptual model of the water-bearing fracture system can be chosen based on them. The case study, to which the proposed methodology has been applied, is a section of the TASS tunnel at 450 m depth in crystalline rock in Aspo Hard Rock Laboratory in Sweden. In this tunnel project an extensive number of tests provided a fine opportunity for analysis and discussions. A set of functional parameters to describe the rock mass for grouting purposes has been suggested. These are: the hydraulic head h; the hydraulic apertures b of the fractures; fracture frequency P-10; the number and orientation of the major fracture sets; and the flow dimension D-q. A set of investigation methods is suggested, aimed at providing the necessary information for high-precision tunnel projects with strict inflow requirements such as the tunnel project studied. Based on these parameters, it is suggested that a conceptual model of the water-bearing fracture system in the rock mass should be chosen. It is shown how this was done in the case study, first in the investigation stage and then an update in the construction stage. Possible ways to adapt the grouting design to the conceptual model are suggested. Selective grouting may be considered for a rock mass with a 2D fracture system, one dominating water-bearing fracture set, when the tunnel orientation is close to perpendicular to this set. For rock mass with a 3D fracture system, two or more water-bearing fracture sets, systematic grouting may be preferable to avoid "moving the water leakage" from one tunnel section to a neighboring section. When the tunnel intersects a fracture zone the focus should be on sealing this zone.
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| 32. |
- Hernqvist, Lisa, 1968, et al.
(författare)
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Analysis of the Transmissivity Development During the Successive Stages of Pre-Grouting of a Tunnel in Hard Rock
- 2009
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Ingår i: Nordic Symposium of Rock Grouting. ; , s. 75-92
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Konferensbidrag (refereegranskat)abstract
- The effect of pre-excavation grouting is in general very difficult to evaluate. The final ingress of water to a tunnel can only be measured after the excavation is completed. The ingress to the tunnel if no grouting were performed is not known. An effort to stepwise evaluate the sealing effect from pre-grouting was carried out for a 20 m section the TASS tunnel at 450 m depth in the Äspö Hard Rock Laboratory in Sweden.Pressure build-up tests were performed in an observational borehole in the tunnel front before and after each grouting round. Inflow tests were performed in the grouting boreholes of each grouting round. Finally, the inflow into the corresponding section of the completed tunnel was measured.The transmissivity was evaluated at all stages of the multi-step grouting and after excavation of the tunnel section. Evaluations of these tests show transmissivity reduction of the grouted rock mass caused by the sealing effect of each grouting event, with the dominant transmissivity decrease produced by the grouting of the first round in the regular fan.
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| 33. |
- Sögaard, Christian, 1990, et al.
(författare)
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Silica sol as grouting material: a physio-chemical analysis
- 2018
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Ingår i: Nano Convergence. - : Springer Science and Business Media LLC. - 2196-5404. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- At present there is a pressing need to find an environmentally friendly grouting material for the construction of tunnels. Silica nanoparticles hold great potential of replacing the organic molecule based grouting materials currently used for this purpose. Chemically, silica nanoparticles are similar to natural silicates which are essential components of rocks and soil. Moreover, suspensions of silica nanoparticles of different sizes and desired reactivity are commercially available. However, the use of silica nanoparticles as grouting material is at an early stage of its technological development. There are some critical parameters such as long term stability and functionality of grouted silica that need to be investigated in detail before silica nanoparticles can be considered as a reliable grouting material. In this review article we present the state of the art regarding the chemical properties of silica nanoparticles commercially available, as well as experience gained from the use of silica as grouting material. We give a detailed description of the mechanisms underlying the gelling of silica by different salt solutions such as NaCl and KCl and how factors such as particle size, pH, and temperature affect the gelling and gel strength development. Our focus in this review is on linking the chemical properties of silica nanoparticles to the mechanical properties to better understand their functionality and stability as grouting material. Along the way we point out areas which need further research.
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| 34. |
- Sögaard, Christian, 1990, et al.
(författare)
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The long term stability of silica nanoparticle gels in waters of different ionic compositions and pH values
- 2018
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 1873-4359 .- 0927-7757. ; 544, s. 127-136
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Tidskriftsartikel (refereegranskat)abstract
- The use of silica nanoparticles for grouting underground tunnels offers an environmentally friendly option compared to organic grouting materials. Silica sols are commercially available and when mixed with an accelerator (salt) they form gels in a predetermined time. While much research has been focused on the practical implementation of silica sols in grouting as well as on the development of physical parameters such as viscosity and strength development, little is known about the long term stability of the resultant silica gels. When placed in rock fractures, parameters such as pH and ionic composition of groundwater may affect the long term stability and functionality of the gels. In this article we use a newly designed test equipment to simulate the behaviour of silica gels when water passes through the gel structure for up to 488 days. The pH and ionic composition of the water is varied to simulate environments that can be experienced by gels used for grouting applications. Results in the form of ionic composition, volume, and pH of leached water were used to evaluate and predict the lifetime of silica gels. The overall results show that several factors such as water flow and the nature of salt, so called accelerator used for gelling have significant effect on the gel life time. Furthermore, it is shown that the accelerator ions leach from the gels; however, the extent to which they are released from the gel depends upon the salt type. From these results we have predicted the lifetime of the 100 mL gels used in our experiments by using a simple numerical model. The predictions show that the total dissolution time for 100 mL gels are up to hundreds of years.
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| 35. |
- Tsuji, M., et al.
(författare)
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Comparison of grouting with silica sol in the Äspö Hard Rock Laboratory in Sweden and Mizunami underground research laboratory in Japan
- 2014
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Ingår i: 8th Asian Rock Mechanics Symposium, ARMS 2014, Royton Sapporo, Hotel and Convention CenterSapporo, Japan, 14-16 October 2014. - 9784907430030 ; , s. 1237-1246
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Konferensbidrag (refereegranskat)abstract
- Silica sol is a material that seems to fulfill the non-hazardous requirement of final repository and capable of penetrating into narrow fractures. The rock grouting strategy with silica sol has been studied and applied for some recent projects in Sweden. The design methodology is based on the determination of the distribution of fracture transmissivity and the theoretical penetration length. In 2008, grouting with silica sol was applied in the construction of a short tunnel at 450 m depth in the Äspö Hard Rock Laboratory (Äspö HRL), the TASS-tunnel. In 2010, a grouting experiment with silica sol was performed at a niche of 300 m depth in the Mizunami Underground Research Laboratory, the MIU-300-niche. Despite the fact that silica sol has been used for a couple of decades for soil consolidation or sealing of fractures, it has seldom been applied as a material for rock grouting during tunneling. The purposes of this study are: • Comparing the grouting work with silica sol in TASS-tunnel and MIU-300m-niche. • Investigating the applicability of the design method used in TASS-tunnel to the grouting experiment performed in MIU-300m-niche. • Suggesting further development of grouting techniques. It was found that although there was quite a difference in the geological conditions and grouting methods, both sites had good sealing quality results. In addition, the Swedish design method seems to be applicable to MIU-300m-niche even with the difference in the fracture aperture distribution in each site. Furthermore, the water inflow in a borehole at MIU-300m-niche has gradually decreased during the three years. One explanation for this good durability of silica sol can be that the grout penetration created a larger overlap between the boreholes than that achieved in TASS-tunnel. A large penetration length of grout minimizes the risk of erosion and/or dilution of grout, thus creating a durable sealing. It can be suggested that the Swedish method can be applied to the design and evaluation of the grouting works in Japanese rock with high intensity of fractures. Moreover, the use of Japanese silica sol or an additional overlap and pumping time might improve the grouting quality in Sweden.
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