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  • 1. Andersson, J. Christer
    et al.
    Martin, C. Derek
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    The Aspo Pillar Stability Experiment: Part II-Rock mass response to coupled excavation-induced and thermal-induced stresses2009In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 46, no 5, p. 879-895Article in journal (Refereed)
    Abstract [en]

    A 1-m-thick pillar was subject to coupled excavation- and thermal-induced stresses to induce brittle rock mass yielding. The yielding strength of the heterogeneous and fractured rock mass consisting of Aspo diorite was evaluated at eighteen discrete locations using data from the displacement, acoustic emission, and thermal monitoring systems. The average rock mass yielding strength was determined to be 0.59 of the uniaxial compressive strength. The onset of dilation in uniaxial laboratory tests, determined from strain gauge data, was found to occur at approximately 0.45 of the uniaxial compressive strength. It was shown that that the onset of acoustic emission events in situ also occurred when the tangential stress exceeded 0.43 of the uniaxial compressive strength. For sites with absence of in situ data it is recommended that this lower-bound value determined from laboratory data may be used for assessing the in situ rock mass yielding strength. Visual observation and displacement monitoring showed that extent of rock mass yielding is sensitive to small changes in the tangential stress magnitudes. It was determined using three-dimensional modelling that changes in the tangential stress magnitude of approximately 1 MPa was sufficient to cause yielding of the pillar to propagate in what appeared to be intact rock. Observations suggest that without this small stress change yielding of the rock mass would not occur. In other words, there appeared to be a well defined boundary, and if the stresses reached this boundary yielding was observed. However, if stresses were only slightly below this boundary yielding or time-dependant processes were not observed over the monitoring period used in the experiment.

  • 2.
    Ansell, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Holmgren, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Mundt, Elisabeth
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering (name changed to Building Service and Energy Systems 2012-03-01).
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Sundquist, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    State-of-the-art och förslag till forskningsprojekt: Drift, underhåll och reparation av trafiktunnlar2007Report (Other academic)
  • 3.
    Bagheri, Mehdi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Baghbanan, Alireza
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Some aspects on model uncertainty in the calculation of block stability using Kinematics Limit Equilibrium2008In: 42nd U.S. Rock Mechanics - 2nd U.S.-Canada Rock Mechanics Symposium, American Rock Mechanics Association , 2008Conference paper (Refereed)
    Abstract [en]

    Kinematics Limit Equilibrium (KLE) is one of the most commonly used approaches for evaluating block stability around underground openings. Model uncertainty in using (probabilistic) KLE has been assessed by comparing block stability results with the results of the Discrete Fracture Network-Distinct Element Method (DFN-DEM) approach. The KLE analysis has been performed based on Monte Carlo random generation for fracture orientations and lengths (probabilistic KLE). The results show that the probabilistic KLE underestimates the unstable block volume. The calculated mean value of unstable block volumes using probabilistic KLE is much smaller than DFN-DEM simulation results, which provide a closer representation of reality.

  • 4.
    Bagheri, Mehdi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    A new analytical solution based on joint relaxation for analyzing symmetrical block stability2013In: International Journal for Numerical and analytical in geomechanics,, ISSN 0363-9061, Vol. 37, no 8, p. 771-786Article in journal (Refereed)
    Abstract [en]

    The magnitude of clamping forces has a significant influence on the estimated ultimate pullout force of a block. The Crawford–Bray equation, which is fundamental in considering clamping forces, is only a function of horizontal stress and block height. Further research to incorporate the influence of induced stress in block stability analysis was considered, but all the previous analytical solutions for analyzing block stability assume a continuum medium to estimate clamping forces and do not allow joint deformations to occur before block movement due to gravity. Assuming a continuous medium to estimate clamping forces leads to an overestimation of block stability and therefore unsafe design. In this paper, an attempt has been made to deepen the understanding of the block failure mechanism and correct the estimated magnitude of clamping forces in a discontinuous medium. A conceptual model is proposed based on the loading–unloading of the block from an in-situ state to failure. Based on this model, an analytical solution has been developed that calculates clamping forces in a discontinuous medium. The validity and model uncertainty of the solution were checked for different conditions. The new analytical solution is both precise and accurate and can be used as a design tool to estimate block stability.

  • 5.
    Bagheri, Mehdi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Application of partial factors to block stability analysisIn: Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, ISSN 1749-9518, E-ISSN 1749-9526Article in journal (Other academic)
  • 6.
    Bagheri, Mehdi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Investigation of model uncertainty for block stability analysis2011In: International journal for numerical and analytical methods in geomechanics (Print), ISSN 0363-9061, E-ISSN 1096-9853, Vol. 35, no 7, p. 824-836Article in journal (Refereed)
    Abstract [en]

    The application of probabilistic design, such as FORM, is expanding rapidly in the design of geotechnical structures. The analytical solution proposed by Crawford and Bray for analyzing block stability can be used as a performance function to carry out probabilistic design. The solution benefits from considering both clamping forces and joint stiffness. However, imperfect assumptions and simplifications in the solution generate model uncertainties. The amount of model uncertainty must be considered in order to assess a reliable design. The purpose of this paper is to identify when the analytical solution is applicable and quantify the model uncertainty of the solution. The amount of model uncertainty for the analytical solution has been assessed for different conditions. The results show that at a shallow depth with a low value of in situ stress ratio (horizontal stress/vertical stress), the analytical solution predicts that the block is stable whereas DEM shows that the block is unstable. The results of the analyses indicate that in cases with low stress ratio, cases with high anisotropy of joint stiffness or the case of a semiapical angle close to the friction angle, the accuracy of the analytical solution is low. Neglecting key parameters, such as the absolute value of joint shear and normal stiffness, vertical in situ stress and its influence on joint relaxation generate model uncertainty in the analytical solution. The analyses show that by having more information about the key parameters, the model uncertainty factor could be identified more precisely.

  • 7.
    Bagheri, Mehdi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Some Aspects of Model Uncertainties of Block Stability Estimation2008In: ARMS 2008, Teheran, 2008, p. 675-681Conference paper (Refereed)
  • 8.
    Bjureland, William
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE).
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Some aspect of reliability-based design for tunnels using observational method (EC7)2015In: EUROCK 2015 & 64th Geomechanics Colloquium, Salzburg, 2015Conference paper (Refereed)
    Abstract [en]

    According to Eurocode 7, the observational method is an accepted design method, where a preliminary design may be updated as the construction progresses. However, Eurocode 7 does not give any advice on how to relate the observations to the acceptable level of safety of the structure. In this paper, we outline a methodology for how to use deformation measurements to predict the final deformation of a circular rock tunnel to calculate the probability of failure. Consequently, the measurements can be used to verify that the design does not violate the specified safety level. The paper shows the potential of combining the observational method with reliability-based design in tunneling

  • 9. Brantberger, M.
    et al.
    Stille, Håkan
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Eriksson, M.
    Controlling grout spreading in tunnel grouting - Analyses and developments of the GIN-method2000In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 15, no 4, p. 343-352Article in journal (Refereed)
    Abstract [en]

    In order to choose the best grouting technique, predictions of the grouting result can be made. Due to uncertainties in the predictions, control of the grouting during ongoing work is an important step towards a successful result. One method to control the grouting is the GIN-method developed and presented by Lombardi and Deere (1993). The method focuses on controlling the grout spreading in order to minimise the risk of hydraulic uplift and achieve a more uniform spreading around a bore hole. However, this method is described with emphasis on dam grouting. In this paper, theories are analysed and developed from a tunnel grouting point of view. A concept of a normalised pressure and normalised grout spreading is presented that at the same time enables control of the grout spreading distance as well as the risk of hydraulic uplift. Calculations based on field data are also done in order to visualise and discuss the potential use of developed theories. Some conclusions from the performed analyses are that other mathematical relations than those stipulated by the GIN-method better account for the risk of hydraulic uplift and that higher pressures than the rule of thumb stipulates could be used in good rock. So far, the concept of normalised pressure and normalised grout spreading is in its first stage and is studied mainly from a theoretical point of view. Further studies are thus needed.

  • 10.
    Carlsson, Mats
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Hintze, Staffan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    On risk management in large infrastructure projects2005In: Proceedings of the 16th International Conference on Soil Mechanics and Geotechnical Engineering, Vols 1-5: Geotechnology In Harmony With The Global Environment, 2005, p. 2785-2788Conference paper (Refereed)
    Abstract [en]

    Large infrastructure projects are in general unique as the conditions and demands vary from one project to another. Furthermore, these projects are often related to risks of different nature due to high technological level, high environmental, public and political focus, long lead and project times, large and complex organizations, complex contracts etc. This paper aims to give some guidelines how to perform a successful management of risks in a large infrastructure project. The main conclusion is that the key to a successful risk management in a large infrastructure projects is early planning and a strict and continuous execution during the entire life-cycle of the project. Good planning and control of the risks enable an organized, comprehensive and iterative approach for identifying and evaluating the risks and give handling options necessary to optimize the project strategy. The management of risks should be performed as early as possible in the life-cycle of a project in order to ensure that critical risks are incorporated into the project plan and addressed with mitigation actions.

  • 11.
    Draganović, Almir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Bleeding and bleeding measurement of cement-based grout2012In: Grouting and deep mixing 2012: Proceedings of the Fourth International Conference on Grouting and Deep Mixing, February 15-18, 2012, New Orleans, Louisiana, American Society of Civil Engineers (ASCE), 2012, no 228 GSP, p. 1681-1690Conference paper (Refereed)
    Abstract [en]

    Grouting is a common method of sealing rock in various geotechnical projects, and the bleeding of cement-based grout is an often-discussed issue. Current cylinder measuring methods for the estimation of the bleeding of cement-based grouts originate from the measurement of the bleeding of cement pastes used in ordinary building practices. Whether bleeding measured with these methods is relevant to bleeding in small fractures in rocks is one of the main questions in this study. This study showed that the bleeding process is very complex and is governed by different physical and chemical processes like sedimentation, consolidation, flocculation and hydration. It also showed that consolidation has little influence on bleeding in fractures. Bleeding in fractures is mainly the result of sedimentation. In addition, the study showed that the results measured using cylinder methods are not relevant for the bleeding of grout in fractures and that voids in the fractures caused by bleeding can be refilled during grouting. The bleeding should occur to a considerably lower extent in rock fractures, if it occurs at all.

  • 12.
    Draganović, Almir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Bleeding and bleeding measurements of cement-based grout2012In: Grout2012, 2012Conference paper (Refereed)
    Abstract [en]

    Grouting is a common method of sealing rock in various geotechnical projects, and the bleeding of cement-based grout is an often-discussed issue. Current cylinder measuring methods for the estimation of the bleeding of cement-based grouts originate from the measurement of the bleeding of cement pastes used in ordinary building practices. Whether bleeding measured with these methods is relevant to bleeding in small fractures in rocks is one of the main questions in this study. This study showed that the bleeding process is very complex and is governed by different physical and chemical processes like sedimentation, consolidation, flocculation and hydration. It also showed that consolidation has little influence on bleeding in fractures. Bleeding in fractures is mainly the result of sedimentation. In addition, the study showed that the results measured using cylinder methods are not relevant for the bleeding of grout in fractures and that voids in the fractures caused by bleeding can be refilled during grouting. The bleeding should occur to a considerably lower extent in rock fractures, if it occurs at all. © 2012 American Society of Civil Engineers.

  • 13.
    Draganović, Almir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Filtration and penetrability of cement-based grout: study performed with a short slot2011In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 26, no 4, p. 548-559Article in journal (Refereed)
    Abstract [en]

    Filtration of cement-based grout during penetration through fractures in rock is an important issue while sealing the rock around tunnels. Whether a type of grout could be designed to penetrate a fracture of a certain aperture without filtration is an interesting question that needs to be further investigated. This study examines the question of whether grout penetration can be measured using our designed measuring method as well as which factors and processes influence the penetrability and filtration of the grout.

    The penetration and filtration of grout are complex processes influenced by many factors such as the grain-size curve of the cement, hydration and flocculation, pressure, grain concentration, and the geometry of constriction.

    The measured results were in agreement with the predicted results, indicating that the filtration process in the given geometry describes correctly.

  • 14.
    Draganović, Almir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Filtration of cement-based grouts measured using a long slot2014In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 43, p. 101-112Article in journal (Refereed)
    Abstract [en]

    Penetrability of cement-based grout is an important issue when sealing the rock around tunnels and measurement of this property of the grout is needed for designing the grouting process and the development of grout. This paper investigates plug-building or the filtration process in a long slot where a slot constriction is placed relatively far from both the "borehole" and the end of the slot. In this slot, a certain shear stress develops before and after a constriction, which may influence plug-building at the constriction. This method is also compared with short slot and penetrability meter. The smallest groutable fracture for all three measured grouts is reasonably close to 75 mu m. Measurements using the long slot showed better penetrability results compared to the short slot and the penetrability meter. The short slot is more practical and gives reasonably good results. The penetrability meter underestimates the penetrability of the grouts.

  • 15.
    Draganović, Almir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Relevanta krav på injekteringsbruk utifrån dagens kunskap / Relevant demands on grout based on actual knowledge2010Conference paper (Other academic)
  • 16.
    Draganović, Almir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Separation och filtrering av cementbaserat injekteringsbruk2010Report (Other academic)
  • 17. Eklund, Daniel
    et al.
    Skärberg, P
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Inträngningsförmåga hos cementbaserade injekteringsmedel2006Conference paper (Other academic)
  • 18. Eklund, Daniel
    et al.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Penetrability due to filtration tendency of cement-based grouts2008In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 23, no 4, p. 389-398Article in journal (Refereed)
    Abstract [en]

    Grouting is a widely used method for strengthening and sealing rock, soil and concrete. The possibilities for sealing Structures are of great importance from both an economic and environmental point of view. The cost of grouting has in certain projects been as high as the cost of blasting and excavating the tunnel. To improve the technique for grouting with cement-based material, it is necessary to examine the properties Of the grout mixture used. The ability of a grout to penetrate cavities, channels and porous material (penetrability) depends on two things: rheology and filtration tendency. Extensive laboratory tests on stable, low w/c-ratio grouts show that the most significant limitation to their penetrability is the tendency of cement grains to agglomerate into an impermeable filter cake. In this report, the ability of a grout to prevent passing obstructions in the flow path Without the cement grains clogging and preventing further penetration is called the filtration tendency. An inert material mixture and a cement-based mixture Lire used in these investigations. The inert material does not react with the water added to the mixture. The cement grouts used are based upon three types of commercially available Portland cements and two Portland cements with modified grain-size distribution Curves. Tests performed show that grain-size and grain-size distribution are of great importance to filtration tendency. According to experiments performed with inert and cement material, it seems to be advantageous for penetrability to have a grain-size distribution that does not contain too many fine or coarse grains. It is reasonable to believe that the grain-size distribution should be relatively steep (narrow grain-size range) between minimum and maximum grain-size. The maximum grain-size is of importance in terms of, for example, d(95). Too great maximum grain-size will prevent penetration of the mixture through obstruction of the flow path. According to the tests, the value of d(95) should be 4-10 times less than the aperture to be penetrated by the cement-based mixture. Small amount of small grain-sizes are also important in achieving low filtration tendency of the grout. This is because of the increased tendency for small grains to flocculate into larger agglomerates, compared to larger grain-sizes. The filtration experiments with cement-based grouts show that parameters such as surface chemistry (use of superplasticisers) and cement chemistry (hydration of cement grains) will strongly affect the filtration tendency of the mixture. To visualize the phenomenon of filtration tendency, it can be investigated to a larger-than-usual scale. Filtration experiments to a scale of approximately 100:1 have been performed in order to observe influences of grain concentration and penetrated slot aperture. It can be seen that the grain-sizes used (monodispersed and inert mixture) should be at least 2-3 times smaller than the aperture to be penetrated by the mixture.

  • 19.
    El Tani, Mohamed
    et al.
    AABuildings, Beirut, Lebanon.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Grout Spread and Injection Period of Silica Solution and Cement Mix in Rock Fractures2017In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, p. 1-16Article in journal (Refereed)
    Abstract [en]

    A systematic presentation of the analytic relations of grout spread to the time period is established. They are divided following the nature of the flow, the property of the mix and the driving process. This includes channel flow between parallel plates and radial flow between parallel discs, nonlinear Newtonian fluids like silica solution, polyurethane and epoxy, and Bingham material like cement-based grout, and three grouting processes at a constant flow rate, constant pressure and constant energy. The analytic relations for the constant energy process are new and complete the relations of the constant flow rate and constant pressure processes. The well-known statement that refusal cannot be obtained during finite time for any injected material at a constant flow rate or constant injection pressure is extended to include the energy process. The term refusal pressure or energy cannot be supported for stop criteria. Stop criteria have to be defined considering confirmed relation of the spread to the time period and of the flow rate to the pressure and spread. It is shown that it is always possible to select a grouting process along which the work will exceed any predefined energy, the consequence of which is that jacking is related to the applied forces and not to the injected energy. Furthermore, a clarification is undertaken concerning the radial flow rate of a Bingham material since there are two different formulations. Their difference is explained and quantified. Finally, it is shown that the applied Lugeon theory is not supported by the analytic relations and needs to be substantially modified.

  • 20. Emmelin, Ann
    et al.
    Brantberger, Martin
    Eriksson, Magnus
    Gustafson, Gunnar
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Rock grouting: Current competence and developmentfor the final repository2007Report (Refereed)
  • 21. Eriksson, M.
    et al.
    Stille, Håkan
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Andersson, J.
    Numerical calculations for prediction of grout spread with account for filtration and varying aperture2000In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 15, no 4, p. 353-364Article in journal (Refereed)
    Abstract [en]

    Grouting as a mean to reduce the ingress of water to underground facilities has been used for decades. With an increased demand for tightness and cost efficiency, the incentive to improve the method has also increased, and the need to understand the governing factors has been focused. The knowledge concerning grouting involves several fields of research, for instance pow in fractured rock and the behaviour of the grouting material. An understanding of these fields is essential in grouting research. Numerical modelling of grout propagation in fracture geometries is one means of achieving such understanding The paper presents how numerical calculations of grout spread and sealing effect can be used for predictions of the grouting result. The calculation concerns pow of grout in a network of conductive elements, representing a fracture geometry with the scope to understand the governing parameters when grouting. The spread of grout is significantly affected by the spatial variability of the fracture aperture. Measurements on grout properties and laboratory experiments show that the grout possesses a limited penetration ability and that filtration of the grout occurs if the aperture of a constriction is smaller than a critical value, i.e. when a filter cake forms in front of constrictions in the pow and the great that passes is filtered. In the paper, a model for filtration of grout is presented. When filtration and limited penetration ability are incorporated in the calculations, additional strong effects are observed. This underlines the need of both a representative geometry, including the fracture variability and measurements of grout properties.

  • 22.
    Eriksson, Magnus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Cementinjektering i hårt berg2005Book (Refereed)
  • 23.
    Gothäll, Rickard
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Risker och möjligheter vid injektering med höga tryck / Risks and possibilities of high pressure grouting2009Conference paper (Other academic)
  • 24.
    Gothäll, Rikard
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Eriksson, Magnus
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    A modification of the random midpoint displacement method for generating rock fracture similar surfaces2005Conference paper (Other academic)
  • 25.
    Gothäll, Rikard
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Fracture dilation during grouting2009In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 24, p. 126-135Article in journal (Refereed)
    Abstract [en]

    Sealing underground excavations from ingress of water constitutes a large part of both the cost and the risk for many infrastructure projects. In this paper we present a mechanical model for the rock mass response when grouting hard jointed rock. The model predicts a stiff and a non-stiff behaviour and a transition between them that is dependent on the relationship between the grouting pressure and the in situ stress conditions. The predictions are consistent with previously published measurements and explain grouting behaviour that has been difficult to model with previous methods.

  • 26.
    Gothäll, Rikard
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Fracture-Fracture Interaction during Grouting2010In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 25, p. 199-204Article in journal (Refereed)
    Abstract [en]

    Sealing of self-supporting underground constructions is often done with grouting or pre-grouting, most often with cementitious grouts. In order to achieve sufficient sealing, fine fractures must be penetrated long distances before the grout hardens. This is achieved with high injection pressures that rivals the in situ stress normal to the fractures. In this paper, the interaction of parallel fractures during high pressure grouting is modelled and the influence of the resulting dilation is discussed. Both linear and non-linear fracture stiffness is used in the modelling.

  • 27.
    Gothäll, Rikard
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Hydrological cycle modelled as a leaky aquifer in well drawdown calculations2006Article in journal (Other academic)
  • 28.
    Gothäll, Rikard
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Rock mass response during high pressure grouting2008Conference paper (Refereed)
    Abstract [en]

    In a recently developed model for fracture dilation during grouting, the fracture stiffness and deformation for in situ conditions is approximated using a minimum of geometrical input. The model describes the loading and unloading behaviour of mated and unmated fractures and predicts a rapid change in stiffness at a critical grouting pressure. In this paper, the implications of this model on real world grouting performance are explored, and the possible implications on grouting design and sealing efficiency is discussed. Data from the construction of a railway tunnel in Sweden (Botniabanan) has been re-evaluated using the new model, showing support for the interpretations regarding the principal behaviour of the rock mass during grouting.

  • 29.
    Gustafson, Gunnar
    et al.
    Chalmers.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stop criteria for cement grouting2005In: Felsbau : Zeitschrift für Geomechanik und Ingenieurgeologie im Bauwesen und Bergbau, ISSN 0174-6979, Vol. 25, no 3, p. 62-68Article in journal (Refereed)
    Abstract [en]

    This paper describes relations between grout penetration and grouting time to derive stop criteria for grouting. These criteria are the basis for the design and execution of grouting operations. More specifically the relations provide the possibility to judge the dimensionality of the flow channels which are penetrated by the grout based on measured flow and pressure. They also provide rules to decide which stop criterion is suitable in order to achieve the required penetration, based on the rock condition and grout properties. An example, taken from real grouting work is analysed and discussed regarding flow system dimensionality and the applicability of stop criteria.

  • 30. Gustafsson, A
    et al.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Krounis, Alexandra
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Krokströmmen valvdamm, stabilitetsanalys i 3D / Stability analysis of the arch dam at Krokströmmen2010Conference paper (Other academic)
  • 31. Gustafsson, A
    et al.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Löwen, K-E
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Analysis, instrumentation and upgrading of the Krokströmmen Arch Dam2010In: Dam Safety: Sustainability in a Changing Environment, 2010Conference paper (Refereed)
  • 32. Gustafsson, A
    et al.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Rytters, K
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Sliding stability analyses of concrete gravity dams founded on rock: proposal for new Swedish guidelines2009Conference paper (Refereed)
  • 33. Gustafsson, Anders
    et al.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Betongdammas glidstabilitet: Förslag på nya riktlinjer2008Report (Other academic)
  • 34. Harrison, J. P.
    et al.
    Alejano, L.
    Bedi, A.
    Ferrero, A. M.
    Lamas, L.
    Mathier, J. -F
    Migliazza, R.
    Olsson, R.
    Perucho, A.
    Sofianos, A.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Virely, D.
    Wittke, M.
    Rock engineering design and the evolution of Eurocode 7: The critical six years to 20202017In: 13th ISRM International Congress of Rock Mechanics, International Society for Rock Mechanics , 2017Conference paper (Refereed)
    Abstract [en]

    In 2010, the Eurocode for Geotechnical Design, EN-1997-1:2004 (CEN, 2004), informally known as Eurocode 7 or EC7, became the Reference Design Code (RDC) for geotechnical design - including rock engineering design - within the European Union (EU). EC7 is one standard within the comprehensive Structural Eurocode suite, which as a whole has been also adopted by a number of other countries beyond the EU. EC7 is thus becoming a key design standard for geotechnical engineering worldwide. As part of the Structural Eurocode suite, EC7 requires designs to adhere to the principles of Limit State Design. However, it is not clear that current rock engineering design practice can satisfy this requirement. In addition, evidence is accumulating that EC7 is currently difficult to apply to, and may even be inappropriate for, rock engineering design. These issues may be due to the fact that the development of EC7 to date took place without any formal input from the international rock mechanics and rock engineering community. In early 2011 under the auspices of CEN (Comité Européen de Normalisation / European Committee for Standardisation), EC7 entered a formal period of maintenance which was aimed at improving the applicability and ease-of-use of the Code. This maintenance cycle will conclude in 2020 with the publication of a revised version of EC7. This paper describes a number of critical aspects for rock engineering in the context of EC7, in particular the following: - the history of the Structural Eurocodes and the concepts they embody; - the nature of Limit State Design and the challenges and opportunities it poses for rock engineering design; - the formal means by which the Structural Eurocode maintenance cycle proceeds; - the plans currently being developed for improving EC7 with regard to rock engineering design and construction; - the unique and vital opportunity for the entire international rock mechanics and rock engineering community to comment on the Code and make suggestions for its improvement.

  • 35.
    Harrison, John P
    et al.
    University of Toronto.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Olsson, Roger
    EC7 and the application of analytical and empirical models to rock engineering2014In: Rock Engineering and Rock Mechanics: Structures in and on Rock Masses - Proceedings of EUROCK 2014, ISRM European Regional Symposium, CRC Press, 2014, p. 1511-1516Conference paper (Refereed)
    Abstract [en]

    The development of EC7 seems to have proceeded with little, if any, input from the rock engineering community, such that the current version of EC7 reveals many difficulties with regard to rock engineering design. Here, following a brief review of various key aspects of the limit state design philosophy adopted by EC7, some of these difficulties in terms of empirical and analytical approaches to rock engineering design are outlined. In particular, EC7 appears to separate the concepts of empiricism, theory, prescriptive measures and observational methods, whereas these are often used in combination in rock engineering design, with empiricism being as a central theme. Similarly, the absence of partial factors for rock mechanics properties is shown to severely limit the applicability of the Design Approaches presented in EC7, and the definitions of Geotechnical Categories given in the code are seen to be unsuitable for some rock engineering designs. Overall, a key difficulty with the code seems to be the lack of recognition of the central and necessary role that empiricism plays in rock engineering design. The challenge for the immediate future is to align EC7 with rock engineering practice, so that it becomes universally applicable to rock engineering design.

  • 36. Hernqvist, Lisa
    et al.
    Fransson, Åsa
    Gustafson, Gunnar
    Emmelin, Ann
    Eriksson, Magnus
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Analyses of the grouting results for a section of the APSE tunnel at Aspo Hard Rock Laboratory2009In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 46, no 3, p. 439-449Article in journal (Refereed)
    Abstract [en]

    The grouting results for a tunnel at a depth of 450 min crystalline rock at Aspo HRL were studied. The aims were to investigate whether the methodology used resulted in a successful grouting design and producing a sufficiently dry tunnel, and whether grout penetration and inflow into the finished tunnel corresponded to the predictions. An analysis was made of data from an original cored borehole, drilled before the tunnel was constructed and mapped thoroughly with regard to fractures and transmissivities. The predicted inflow into the tunnel was calculated and found to be four times higher than the measured inflow. The latter was 51/min a long the 70 m tunnel, considered to be a good result at the current depth. New cored control boreholes were drilled along a section of the tunnel. The inflow positions and quantities in these holes, and the positions of grout found in the corresponding cores, were compared with the data from the original borehole. It was found that at the predicted positions of larger fractures, grout was observed and there was no inflow, showing that these had been successfully sealed. At the predicted positions of small fractures, no grout was visible in the cores, and small inflows showed that the grout had not sealed these fractures. The results indicated that cement-based grout successfully sealed fractures down to a hydraulic aperture of about 50 mm but not below 30 mm. This concurs with the initial design aimed at sealing fractures larger than 50 mm.

  • 37.
    Hintze, Staffan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Carlsson, Mats
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Effektivare hantering av geotekniska risker i infrastrukturprojekt2006In: Bygg & teknik, ISSN 0281-658X, no 2, p. 22-28Article in journal (Other academic)
    Abstract [en]

    Under de senaste årtionden har många infrastrukturprojekt blivit väsentligt dyrare och tagit längre tid att genomföra än beräknat. En stor del av projekten har dessutom orsakat kostsamma tvister för flera parter i projektet och för samhället. Kostnaderna för skador på grund av bristande hänsyn till de geotekniska faktorerna står för en betydande del av totalkostnaden.

  • 38. Holmberg, Mats
    et al.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Observationsmetodens grunder och dess tillämpning på design av konstruktioner i berg2007Report (Other academic)
  • 39.
    Holmberg, Mats
    et al.
    Tunnel Engineering AB.
    Tsuji, Masakuni
    Shimizu Corporation.
    Stille, Björn
    SWECO AB.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Evaluation ofpre-grouting for the City Line project using the RTGC method2012Conference paper (Refereed)
  • 40.
    Holmberg, Mats
    et al.
    Tunnel Engineerning AB.
    Tsuji, Masakuni
    Shimizu Corporation.
    Stille, Björn
    SWECO AB.
    Yaghoobi Rafi, Jalaleddin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Evaluation of pre-grouting with the RTGC method and results from the City Line project2013In: 7th Nordic Grouting Symposium, Stockholm: Rock Engineering Research Foundation , 2013, p. 135-145Conference paper (Other academic)
  • 41.
    Isaksson, Therese
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Model for estimation of time and cost for tunnel projects based on risk evaluation2005In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 38, no 5, p. 373-398Article in journal (Refereed)
    Abstract [en]

    In the planning and procurement phases of tunnelling projects, numerous decisions have to be made regarding tender price and budget. Many case studies have shown that, in practice, the predicted costs and time schedules are often exceeded. This paper describes a study of the various risk factors in machine tunnelling and their differing impacts on cost and time. It has been concluded from the study that it is important to make a clear distinction between normal cost and time, and the undesirable events that cause exceptional cost and time. Existing decision-aid estimation models consider variation of the risk factors, but do not consider normal cost or time separately from undesirable events. Usually, estimations of project cost and time are made in a deterministic manner, but this does not allow one to consider uncertainty in cost and time variables. However, if the variables are treated probabilistically, the total cost of tunnelling can be expressed as a distribution curve, and a decision can be made on the tunnelling method by comparing the respective cost and time distributions. Based on such decisions, the budget and tender price can be determined separately, both by the client and contractor respectively. To meet the demands placed on decision-making for tender and procurement for currently favoured construction-contracting methods, a new model for estimating tender price and budget has been developed, and is described in this paper. This estimating technique has been applied to a case study of the Grauholz Tunnel. The predictions obtained from the estimation model are shown to be realistic, as the total construction cost and time obtained from the model correspond fairly well to the actual construction cost and time. The separate estimation of normal cost and time and exceptional cost and time contribute to the clarity of the results. The use of the proposed model also shows that the tunnelling method most suitable for the actual geological and hydrogeological conditions can be selected by this method.

  • 42.
    Johansson, Fredrik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Bagheri, Mehdi
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Variation of mechanical parameters of a slightly weathered joint in granite estimated from fourteen shear tests2010In: ROCK MECHANICS IN CIVIL AND ENVIRONMENTAL ENGINEERING, 2010, p. 223-226Conference paper (Refereed)
    Abstract [en]

    Describing the mechanical parameters of a rock joint with single values is difficult since rock has a natural spatial variation. In addition to this, the interpretation of the results is dependent on the number of tests. Despite this fact, input data for these parameters are often given with a deterministic value. This paper presents the results of fourteen shear tests tested under a constant normal stress of approximately 0.8 MPa. The samples were taken from a slightly weathered rock joint in granite. Basic friction angle and dilation angle, together with shear and normal stiffness, are evaluated. Based on the results, mean values and standard deviations together with coefficient of variations for the different parameters are presented. After that, different statistical distributions for the parameters are compared. Finally, the results are compared against calculated values derived from commonly used equations.

  • 43.
    Johansson, Fredrik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Damasceno, Davi
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Jan
    Naturgasteknik AB.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Investigation of research needs regarding the storage of hydrogen gas in lined rock caverns: Prestudy for Work Package 2.3 in HYBRIT Research Program 12018Report (Other academic)
    Abstract [en]

    The objective of HYBRIT RP1 is to explore and assess pathways to fossil-free energy-mining-iron-steel value chains and thereby provide a basis for industrial development activities and the necessary future transformative change in this field. A large-scale storage capacity for hydrogen gas is an important component of the proposed HYBRIT concept. Underground storage in lined rock caverns provides a reasonable option: a large-scale demonstration plant for storage of natural gas was constructed in Sweden in 2002 and has operated safely since then. Considering that this lined rock cavern facility was constructed for natural gas, the present report investigates the current research needs to allow for underground storage of hydrogen gas in such a facility. This will serve as a basis for the research in Work Package 2.3 of HYBRIT RP1.

    Studying the experiences from decades of Swedish and international research and practice on the construction of underground gas storage facilities, the conclusion is that the lined rock cavern concept seems a reasonable way forward. In terms of rock engineering research, there are currently no critical research issues; however, a development of a previously proposed risk-based design framework for lined rock caverns may further strengthen the ability to manage risks related to underground gas storage facilities. The report identifies several potential research questions on this topic to be further studied: development of a risk-based design approach using subset simulation, the optimization potential of the concrete thickness in the lining, and the effect of spatial variation of rock mass properties on a location’s suitability for the storage facility.

    Additionally, the report identifies the potential effect of hydrogen embrittlement on the steel lining as a critical research issue to ensure safe storage of hydrogen gas in lined rock caverns. However, as this issue is not related to rock engineering, but a material issue, it will not be covered further in Work Package 2.3.

  • 44.
    Johansson, Fredrik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    A conceptual model for the peak shear strength of fresh and unweathered rock joints2014In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 69, p. 31-38Article in journal (Refereed)
    Abstract [en]

    Several criteria have been proposed over the years in order to predict the peak shear strength of rock joints.The most widely used criterion is the JRC-JCS criterion by Barton. It says that changes in the peak shear strength originate from surface roughness, joint wall compressive strength and normal stress. A limitation with this criterion is that the contribution from roughness could be overestimated for natural and mismatched joints if the joint roughness coefficient, JRC, is estimated based on the direct profiling method. To account for this effect, Zhao introduced the joint matching coefficient, JMC, which accounts for the matedness of the joint. In addition to this, it is known that the scale of the sheared joint could affect the peak shear strength. However, no criterion exists that describes how roughness, matedness and scale interact. In this paper, a conceptual model is proposed. The model is based on adhesion and fractal theory, measurements of surface roughness and the anticipated variation of the number and size of the contact points. The model proposes how the compressive strength and the roughness of the joint surface together with the matedness of the joint interact in order to form the shear strength of the joint under constant normal load conditions. The model also suggests an explanation for the scale effect of rock joints with respect to the surface roughness.

  • 45.
    Johansson, Fredrik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    A simplified model for estimation of horizontal rock displacements in connection to Krokströmmen arch dam2004Conference paper (Other academic)
  • 46. Kobayashi, Shinji
    et al.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Design for rock grouting basedon analysis of grout penetration: Verification using Äspö HRL dataand parameter analysis2007Report (Refereed)
  • 47. Kobayashi, Shinji
    et al.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Gustafson, Gunnar
    Chalmers.
    Stille, Björn
    Real Time Grouting Control Method: Development and application usingÄspö HRL data2008Report (Refereed)
  • 48. Larsson, S.
    et al.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Olsson, L.
    On horizontal variability in lime-cement columns in deep mixing2006Conference paper (Refereed)
    Abstract [en]

    The variability with respect to results from hand-operated penetrometer tests on lime-cement column cross-sections is investigated by means of spatial correlation structures. Experimental directional semi-variograms are evaluated for a large number of column cross-sections from two field tests. Analyses of variance (ANOVA) are performed in order to investigate the influence of various factors in the installation process on the inherent variability. The paper also briefly discusses the concept of sufficient mixing: the link between the mixing process and the mechanical system. The results have been interpreted within the framework of variance reduction based on an averaging model for axially loaded columns. The results from the two field tests show that the radius is the dominating variable in the variability, and different types of correlation structure can be obtained in spite of the fact that they have been equally installed. The mechanical mixing work does not significantly influence the type of spatial correlation structure. Furthermore, a simple design consideration shows that the variance reduction has a major influence on the determination of the partial factor of safety.

  • 49.
    Larsson, Stefan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Olsson, Lars
    On horizontal variability in lime-cement columns in deep mixing2005In: Geotechnique, ISSN 0016-8505, E-ISSN 1751-7656, Vol. 55, no 1, p. 33-44Article in journal (Refereed)
    Abstract [en]

    The variability with respect to results from hand-operated penetrometer tests on lime-cement column cross-sections is investigated by means of spatial correlation structures. Experimental directional semi-variograms are evaluated for a large number of column cross-sections from two field tests. Analyses of variance (ANOVA) are performed in order to investigate the influence of various factors in the installation process on the inherent variability. The paper also briefly discusses the concept of sufficient mixing: the link between the mixing process and the mechanical system. The results have been interpreted within the framework of variance reduction based on an averaging model for axially loaded columns. The results from the two field tests show that the radius is the dominating variable in the variability, and different types of correlation structure can be obtained in spite of the fact that they have been equally installed. The mechanical mixing work does not significantly influence the type of spatial correlation structure. Furthermore, a simple design consideration shows that the variance reduction has a major influence on the determination of the partial factor of safety.

  • 50. Lucian, Charles
    et al.
    Hintze, Staffan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Geotechnical Strategies for Poverty Reduction in Kibaha, Tanzania: Best Way Forward for Damaged Buildings on Expansive Soils2006Conference paper (Refereed)
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