| 1. |
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| 2. |
- Holmberg, M., et al.
(författare)
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Evaluation of pre-grouting for the city line project using the RTGC method
- 2012
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Ingår i: ISRM International Symposium - EUROCK 2012. - : International Society for Rock Mechanics.
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Konferensbidrag (refereegranskat)abstract
- An access tunnel for the City Line project in Stockholm was excavated in the early parts of 2010. The works also included pre-grouting with cement. The performance of pre-grouting operation was evaluated for 14 continuous fans that included 326 grouted holes. A method called “Real Time Grouting Control (RTGC)”was used in the analysis. It is shown how the RTGC method can be used to investigate the effectiveness of existing stop criteria. It is first time an evaluation using RTGC carried out in this magnitude. The water inflow to the tunnel after grouting satisfied requirements. The grouting effect is quantified by assessments of the average conductivity of the rock mass and of the grout spread outside the tunnel. The evaluation indicates that the stop criteria in the design were chosen conservatively relative to the achieved grouting results. A model is discussed where the required grout spread is used as a design parameter to quantify the potential for reducing the pumping time.
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| 3. |
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| 4. |
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Stille, Björn, 1969, et al.
(författare)
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Experience with the real time grouting control method
- 2009
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Ingår i: Geomechanics and Tunneling. - : Wiley. - 1865-7362 .- 1865-7389. ; 2:5, s. 447-459
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Tidskriftsartikel (refereegranskat)abstract
- A new concept of "real time grouting control method" is described by which grout penetration and grouting control are made applicable in real time by applying theories for grout spread. The stop criterion with this method can be related to achieved grout spread, and grouting may be considered complete when the grout penetration for the smallest fracture to be sealed is above a predetermined target value, or before the grout penetration for the largest fracture aperture reaches a certain maximum limiting value. It might also be possible by online monitoring of the process to predict the course of the grout spread and flow and to analyse the risk of uplift and jacking. Four tunnel projects in Sweden are presented in the paper. These references indicate that the real time grouting control method may be applicable to real grouting design and control.
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| 9. |
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| 10. |
- Stille, Björn, 1969, et al.
(författare)
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Experiences With Real Time Grouting Control Method
- 2010
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Ingår i: Bergmekanikdag : föredrag vid Bergmekanikdag i Stockholm 8 mars 2010.. - 0281-4714. ; , s. 119-132
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In the paper the concept of “Real Time Grouting Control Method” is described in order to calculate the grout penetration and to control grouting in real time by applying developed theories for grout spread. The stop criterion can with this method be related to achieved groutspread such as the fact that grouting is completed when the grout penetration for the smallest fracture that has to be sealed is above a certain minimum value (target value) or before the grout penetration for the largest fracture aperture reaches a certain maximum value (limitingvalue).It might also be possible by following the ongoing grouting minute by minute to predict the course of the grout flow and spread and also analyze the risk for uplift and jacking. These issues will also be discussed in the paper.Verification of the “Real Time Grouting Control Method”, with field data from four tunnel projects in Sweden is presented in the paper. The calculated flow dimensionality, the calculated fracture apertures and the calculated grout flows were quite close to thosemeasured. This indicates that the “Real Time Grouting Control Method” may be applicable to real grouting design and control.
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| 11. |
- Alejano, L. R., et al.
(författare)
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Rock engineering design and the evolution of Eurocode 7
- 2013
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Ingår i: ISRM International Symposium - EUROCK 2013. - : International Society for Rock Mechanics. - 9781138000803 ; , s. 777-782
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Konferensbidrag (refereegranskat)abstract
- The Eurocode for Geotechnical Design, EN-1997-1:2004, informally known as Eurocode 7 or EC7, was fully implemented within the European Union in 2010. This Eurocode is intended to apply to all geotechnical engineering design, including rock engineering. In recognition that all codes must continue to evolve in order to remain applicable, and the long time that such evolution takes, work is already underway under the auspices of the European Committee for Standardisation, CEN, to identify how the code should develop for future revisions. This paper presents a summary of the maintenance procedures for Eurocodes in general and the specific maintenance work currently being undertaken on EC7 in respect of rock engineering design. It also highlights potential future development of EC7, and the need for enthusiastic involvement by the European rock engineering community to direct these developments.
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| 12. |
- Andersson, J. Christer, 1974-
(författare)
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Rock Mass Response to Coupled Mechanical Thermal Loading : Äspö Pillar Stability Experiment, Sweden
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The geological disposal of nuclear waste, in underground openings and the long-term performance of these openings demand a detailed understanding of fundamental rock mechanics. A full scale field experiment: Äspö Pillar Stability Experiment was conducted at a depth of 450 m in sparsely fractured granitic rock to examine the rock mass response between two deposition holes. An oval shaped tunnel was excavated parallel to the σ3 direction to provide access to the experiment and also provide elevated stress magnitudes in the floor. In the tunnel floor two 1.75-m diameter 6-m deep boreholes were excavated so that a 1-m thick pillar was created between them. In one of the holes a confinement pressure of 700 kPa was applied and in the other displacement transducers were installed. The pillar volume was monitored by an Acoustic Emission System. Spatially distributed thermocouples were used to monitor the temperature development as the pillar was heated by electrical heaters. The excavation-induced stress together with the thermal-induced stress was sufficient to cause the wall of the open borehole to yield. The temperature-induced stress was increased slowly to enable detailed studies of the rock mass yielding process. Once the rock mass loading response was observed, the rock mass was unloaded using a de-stress slotting technique.This thesis focuses on the in-situ study of the rock mass response to coupled mechanical thermal loading and thermal-mechanical unloading. The experiment, its design, monitoring and observations are thoroughly described. An estimate of the yielding strength of the rock mass is presented and compared with laboratory test and results from other rock mass conditions reported elsewhere in the open literature. General conclusions about the effect of the confining pressure and the observations from the unloading of the pillar are also presented.Important findings are that the yielding strength of the rock mass has been successfully determined, low confinement pressures significantly affects the onset of yielding, the primary mode of fracture initiation and propagation is extensional, no significant time dependency of the yielding process was observed. The unloading studies also indicated that what appeared to be shear bands likely was a propagating zone of extensile failure that weakened the rock so that displacements in the shear direction could occur.
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| 13. |
- Andersson, J. Christer, et al.
(författare)
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The Aspo Pillar Stability Experiment : Part II-Rock mass response to coupled excavation-induced and thermal-induced stresses
- 2009
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 46:5, s. 879-895
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 14. |
- Bagheri, Mehdi, et al.
(författare)
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A new analytical solution based on joint relaxation for analyzing symmetrical block stability
- 2013
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Ingår i: International Journal for Numerical and analytical in geomechanics. - : Wiley. - 0363-9061. ; 37:8, s. 771-786
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 15. |
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| 16. |
- Bagheri, Mehdi
(författare)
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Block stability analysis using deterministic and probabilistic methods
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents a discussion of design tools for analysing block stability around a tunnel. First, it was determined that joint length and field stress have a significant influence on estimating block stability. The results of calculations using methods based on kinematic limit equilibrium (KLE) were compared with the results of filtered DFN-DEM, which are closer to reality. The comparison shows that none of the KLE approaches– conventional, limited joint length, limited joint length with stress and probabilistic KLE – could provide results similar to DFN-DEM. This is due to KLE’s unrealistic assumptions in estimating either volume or clamping forces. A simple mechanism for estimating clamping forces such as continuum mechanics or the solution proposed by Crawford-Bray leads to an overestimation of clamping forces, and thus unsafe design. The results of such approaches were compared to those of DEM, and it was determined that these simple mechanisms ignore a key stage of relaxation of clamping forces due to joint existence. The amount of relaxation is a function of many parameters, such as stiffness of the joint and surrounding rock, the joint friction angle and the block half-apical angle. Based on a conceptual model, the key stage was considered in a new analytical solution for symmetric blocks, and the amount of joint relaxation was quantified. The results of the new analytical solution compared to those of DEM and the model uncertainty of the new solution were quantified. Further numerical investigations based on local and regional stress models were performed to study initial clamping forces. Numerical analyses reveal that local stresses, which are a product of regional stress and joint stiffness, govern block stability. Models with a block assembly show that the clamping forces in a block assembly are equal to the clamping forces in a regional stress model. Therefore, considering a single block in massive rock results in lower clamping forces and thus safer design compared to a block assembly in the same condition of in-situ stress and properties. Furthermore, a sensitivity analysis was conducted to determine which is the most important parameter by assessing sensitivity factors and studying the applicability of the partial coefficient method for designing block stability. It was determined that the governing parameter is the dispersion of the half-apical angle. For a dip angle with a high dispersion, partial factors become very large and the design value for clamping forces is close to zero. This suggests that in cases with a high dispersion of the half-apical angle, the clamping forces could be ignored in a stability analysis, unlike in cases with a lower dispersion. The costs of gathering more information about the joint dip angle could be compared to the costs of overdesign. The use of partial factors is uncertain, at least without dividing the problem into sub-classes. The application of partial factors is possible in some circumstances but not always, and a FORM analysis is preferable.
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| 17. |
- Bagheri, Mehdi, et al.
(författare)
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Investigation of model uncertainty for block stability analysis
- 2011
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Ingår i: International Journal for Numerical and Analytical Methods in Geomechanics. - : Wiley. - 0363-9061 .- 1096-9853. ; 35:7, s. 824-836
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 18. |
- Bagheri, Mehdi
(författare)
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Model uncertainty of design tools to analyze block stability
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Block failure is one of the most common failure modes in tunnels. Design tools have some simplifications and, therefore, they also have some model uncertainties. The purpose of this licentiate thesis is to assess the model uncertainty for different design tools in order to estimate block stability. Different approaches of kinematic limit equilibrium (KLE) including conventional KLE, limited joint length, limited joint length and stress field consideration and probabilistic KLE were compared to that of DFN-DEM. In this approach, the results of the calibrated DFN-DEM with field mapping were considered to be of true value. The results show that the conventional KLE is overdesign due to it’s over simplification. By considering fracture length and stress field, the volume of predicted unstable blocks is reduced. The probabilistic approach of KLE by considering finite joint length and stress field predicts the volume of unstable blocks to be lower than DFN-DEM approach. Therefore there is a great model uncertainty of our standard design tools for block stability analysis. The assumption made in this study is that the results from DEM were considered to have a true value; the results from analytical solution based on joint relaxation process were compared to those of DEM in a different condition of depth, K0, apical and friction angle, Kn and Ks value, and ratio of Kn/Ks. The comparison shows that for shallow depth with K0 less than 1, analytical solution leads to an overestimation of block stability. The analytical solution predicts that the block is stable, while the analyses from numerical solution show the block is unstable. The analyses show that by increasing K0, accuracy of analytical solution also increases. Moreover, for the cases with close value of friction angle to semi-apical angle, the use of analytical solution is not recommended. As the ratio of Kn/Ks increases, the accuracy of analytical solution decreases. Increasing the angle ratio (ratio between semi-apical angle to friction angle) is one source of increasing uncertainty in the model. The analytical solution is very uncertain in cases with a low value of K0, and a high value of stiffness ratio and angle ratio. On the other hand, the analytical solution is more certain in conditions with a high value of K0 and a low value of stiffness ratio and angle ratio. According to current information (K0, angle ratio, stiffness ratio), one can determine the value of model uncertainty by using the diagrams presented in Chapter 6 of the thesis. The analyses show that by having more information about the key parameters, the model uncertainty could be identified more precisely. However, having more information means spending more money, and this increase in cost must be compared to the cost of failure or delay in the project or overdesign.
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| 19. |
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| 20. |
- Bagheri, Mehdi, et al.
(författare)
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Some aspects on model uncertainty in the calculation of block stability using Kinematics Limit Equilibrium
- 2008
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Ingår i: 42nd U.S. Rock Mechanics - 2nd U.S.-Canada Rock Mechanics Symposium. - : American Rock Mechanics Association.
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 21. |
- Bjureland, William, et al.
(författare)
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Some aspect of reliability-based design for tunnels using observational method (EC7)
- 2015
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Ingår i: EUROCK 2015 & 64th Geomechanics Colloquium. - Salzburg.
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Konferensbidrag (refereegranskat)abstract
- 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
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| 22. |
- Brantberger, M., et al.
(författare)
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Controlling grout spreading in tunnel grouting - Analyses and developments of the GIN-method
- 2000
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Ingår i: Tunnelling and Underground Space Technology. - 0886-7798 .- 1878-4364. ; 15:4, s. 343-352
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 23. |
- Carlsson, Mats, et al.
(författare)
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On risk management in large infrastructure projects
- 2005
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Ingår i: Proceedings of the 16th International Conference on Soil Mechanics and Geotechnical Engineering, Vols 1-5. - 9789059660274 ; , s. 2785-2788
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 24. |
- Draganović, Almir, et al.
(författare)
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Bleeding and bleeding measurement of cement-based grout
- 2012
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Ingår i: Grouting and deep mixing 2012. - Reston, VA : American Society of Civil Engineers (ASCE). - 9780784412350 ; , s. 1681-1690
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 25. |
- Draganovic, Almir, 1964-
(författare)
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Bleeding and Filtration of Cement-Based Grout
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Grouting is a common method of sealing rock around tunnels to reduce or stop water inflow. Successful grouting significantly minimizes the maintenance cost and safety of the tunnel. Some questions about bleeding and penetrability of the grouts have to be examined more closely to carry out a successful grouting. Bleeding of cement-based grout is a complex problem. Measuring methods used today originate from the measuring of the bleeding of cement pastes used in ordinary building industry. Whether bleeding measured with a standard method is relevant for bleeding in small fractures in rocks is one of the main questions in this study. The aim of the study is to illustrate what really happens with a grout during bleeding and which factors and processes influence it. In this way relevant measuring methods can be developed as well as the knowledge regarding interpretation of the measured results. The study has shown the most important factors which governs bleeding in cement-based grout. It has also shown that the results measured with standard methods are not relevant for bleeding of grout in rock joints and that voids in the joints caused by bleeding could be refilled during grouting itself. An important aspect of grouting is penetration of the grout. The penetration is defined as the length of how far grout penetrates in the rock through fractures from a bore hole. Filtration of the grout is a result of a plug building at fracture constrictions which reduces the penetrability of the grout. This is the other important issue discussed in the study which examines the question whether this can be measured by some measuring method and which factors and processes influence penetrability and filtration. A hypothesis of how the factors w/c ratio, pressure and relative constriction influence penetrability are presented and tested by special constructed measuring equipment. The results obtained by this measuring equipment are compared with the results measured with a penetrability meter.
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| 26. |
- Draganović, Almir, 1964-, et al.
(författare)
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Filtration and penetrability of cement-based grout : study performed with a short slot
- 2011
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier. - 0886-7798 .- 1878-4364. ; 26:4, s. 548-559
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 27. |
- Draganović, Almir, 1964-, et al.
(författare)
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Filtration of cement-based grouts measured using a long slot
- 2014
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798 .- 1878-4364. ; 43, s. 101-112
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 28. |
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| 29. |
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| 30. |
- Draganovic, Almir
(författare)
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Separations- och filtreringsstabilitet hos cementbaserat injekteringsbruk
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bleeding of cement based grout Bleeding of cement based grout is a complex problem. How it occurs and which basic mechanism causes and influences bleeding have been questions for discussion. Therefore the aim of the thesis is to illustrate what really happens with grout during bleeding and which factors influence it. In this way relevant measuring methods can be developed as well as the knowledge regarding how to interpret measuring results to joints in rock. The bleeding tests show that there are two basic mechanisms which cause bleeding. They are sedimentation and consolidation. It also means that the bleeding process is influenced by sample height. It was found that bleeding of coarse cement (ANL) was mainly a result of sedimentation of the grout. Experiment with fine cement (INJ30; d95<30 µm) shows that the consolidation part of bleeding was larger. The study shows that the bleeding process for a low sample height (10 mm) occurs fast. Extrapolation of experiment results and theoretical analysis shows that bleeding in a joint happens very fast and takes place during grouting itself. It means that results measured by standard methods can not be applied straight off for joints in rock. Theoretically bleeding occurs relatively slowly in vertical or inclined joints due to increased height. Bleeding will be resisted by arching and hardening. Reasonably, very little bleeding will take place. Filtration of cement based grout How far grout penetrates into a joint is not just influenced by the rheology of the grout like viscosity and shear strength, but also by the tendency of the grout to get stuck which means to build a plug. Factors which influence the building of a plug are properties of the grout, geometry of the joints including rawness of the joints and proceeding of the grouting. Today there are many different ways to measure filtration of a grout or the building of a plug. The different methods give different results and thus the importance of the influence of different factors is interpreted differently. The experiments in this thesis are done in a 100 mm long, 50 mm wide aperture with 1 mm width. Thereafter the width of the aperture decreases to 0.02 – 0.3 mm over a 10 mm long distance. The results of the experiments in this thesis, measured by own method, show that the best penetration ability with respect to filtration has a grout based on relatively fine-graded cement (INJ30; d95<30 µm).The penetrability of the grout based on more graded cement decreases because of flocculation. In total tens measurements have been done. The measurements confirm others’ experiments which show that the concentration of fine-graded particles (< 4 µm) has a large influence on flocculation and with that the building of larger grains. It is important to remind that the mixing of grout has been done by a laboratory mixer, which is not a mixer of colloidal type. This issue has to be further tested. The research shows that filtration of grout is also influenced by grain size of cement and the water cement ratio. The filtration test carried out by own measuring method with varying pressure showed a better penetrability for a larger pressure. It influenced both arching and erosion of the accumulated particles.
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| 31. |
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| 32. |
- Eklund, Daniel, 1975-
(författare)
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Penetrability due to filtration tendency of cement based grouts
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Grouting as a method of strengthening and sealing rock, soil and concrete is widely used. The possibilities of sealing structures are of great importance from both an economical and environmental point of view. The cost of grouting has in certain projects been as high as the cost for the blasting and excavation of the tunnel. To improve the technique of grouting with cement based material, it is necessary to focus on the properties of the used grout mixture. The ability of a grout to penetrate cavities, channels and porous material, the penetrability, depends on two things, the theology and the filtration tendency. Extensive laboratory tests on stable, low w/c-ratio, injection grouts show that the most significant limitation to their penetrability is the tendency of cement grains to agglomerate into an impermeable filter cake. The properties of a grout that may prevent passing obstructions in the flow path without the cement grains clogging and preventing further penetration is in this work called filtration tendency. An inert material mixture and a cement-based mixture are used for the investigations in this work. The inert material, which is crushed dolomite stone, does not react with the added water in the mixture. The used cement grouts are based upon three types of commercial available Portland cements and four Portland cements with modified grain size distribution curves. Performed tests show that the grain size and grain size distribution is of great importance for the filtration tendency. According to performed experiments with inert and cement material, it seems to be advantageous for the penetrability to have a grain size distribution that contains neither 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 d95. Too large maximum grain size will prevent penetration of the mixture through obstructions in the flow path. According to performed tests, the value of d95, should be between 4-10 times smaller than the aperture to be penetrated by the cement based mixture. The small grain sizes are also of importance in order to achieve a low filtration tendency of the grout. This is because of the increased tendency for the small grains to flocculation into larger agglomerates, compared to larger grain sizes. The filtration experiments with cement based grouts show that influences of parameters like surface chemistry (use of superplastisisers) 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 on a larger scale than usually takes place. Filtration experiments in the scale of approximately 100:1 have been performed in order to see influences of grain concentration, grain shape and the penetrated slot aperture. It can be seen that used grain sizes (monodisperse and inert mixture) should be approximately at least 2-3 times smaller than the aperture to be penetrated by the mixture. Numerical experiments of filtration tendency have also been performed to investigate the possibilities to numerically simulate the influence of grain concentration and slot aperture. The numerical experiments are based on Eulerian flow modelling.
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| 33. |
- Eklund, Daniel, et al.
(författare)
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Penetrability due to filtration tendency of cement-based grouts
- 2008
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798 .- 1878-4364. ; 23:4, s. 389-398
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 34. |
- El Tani, Mohamed, et al.
(författare)
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Grout Spread and Injection Period of Silica Solution and Cement Mix in Rock Fractures
- 2017
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Ingår i: Rock Mechanics and Rock Engineering. - : Springer. - 0723-2632 .- 1434-453X. ; 50:9, s. 2365-2380
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 35. |
- Elfgren, Lennart, Senior Professor, 1942-, et al.
(författare)
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Byggforskning i samverkan : Slutrapport
- 2005
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Rapport (populärvet., debatt m.m.)abstract
- Genom att bedriva internationellt slagkraftig forskning i Sverige säkerställs att• den senaste kunskapen finns tillgänglig inom landet• unga människor kan ges en internationellt konkurrenskraftig utbildning inom byggområdet• byggsektorn kan försörjas med arbetskraft som har god kompetens.På Chalmers, KTH, LTH och LTU finns ca 65 forskningsledare och därutöver ytterligare ca 160 seniorforskare. De handleder ca 445 doktorander varav ca 135 är industridoktorander som forskarutbildar sig på minst halvtid. Under den senaste treårsperioden producerades i medeltal ca 70 forskarexamensekvivalenter per år (en licentiatexamen motsvarar en halv ekvivalent och arbetet från licentiat till doktor ytterligare en halv ekvivalent).Vid en konferens på Arlanda den 14-15 oktober 2004 samlades ett 50-tal av forskningsledarna och diskuterade gruppvis och i plenum. Huvudfrågorna var hur man på bästa sätt kan utnyttja de resurser som finns och formera sig för att bli mer slagkraftiga såväl nationellt som internationellt. Före konferensen ombads forskningsledarna att besvara ett antal frågor rörande omfattningen på sin verksamhet. Alla har svarat om än med något olika detaljeringsgrad. Svaren har utgjort en bas för de diskussioner som ägde rum inom följande sex teman:• Konstruktion och mekanik• Geoteknologi• Vatten• Byggteknik, installationsteknik, akustik och brand• Management, ekonomi och juridik• TrafikFöljande förslag framkom om fördjupat samarbete, samordning och effektivisering av verksamheten:• öka profileringen och samverkan i forskningen• utveckla och genomför ett nationellt forskarutbildningsprogram• samverka inom grundutbildningen avseende kursutveckling, litteratur och hjälpmedel• profilera grundutbildningen mellan högskolorna• samutnyttja laboratorieresurser• agera gemensamt i forsknings- och utbildningspolitiska frågor• samverka i EU-program
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| 36. |
- Elfgren, Lennart, et al.
(författare)
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Kan högskolorna samarbeta...!
- 2005
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Ingår i: V-byggaren : väg- och vattenbyggaren. - 0283-5363. ; :2, s. 38-40
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 37. |
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| 38. |
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| 39. |
- Eriksson, M., et al.
(författare)
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Numerical calculations for prediction of grout spread with account for filtration and varying aperture
- 2000
-
Ingår i: Tunnelling and Underground Space Technology. - 0886-7798 .- 1878-4364. ; 15:4, s. 353-364
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 40. |
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| 41. |
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| 42. |
- Gothäll, Rikard, 1976-, et al.
(författare)
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Fracture dilation during grouting
- 2009
-
Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798 .- 1878-4364. ; 24, s. 126-135
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 43. |
- Gothäll, Rikard, et al.
(författare)
-
Fracture-Fracture Interaction during Grouting
- 2010
-
Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798 .- 1878-4364. ; 25, s. 199-204
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 44. |
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| 45. |
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| 46. |
- Gothäll, Rikard, et al.
(författare)
-
Rock mass response during high pressure grouting
- 2008
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 47. |
- Gothäll, Rikard
(författare)
-
Rock mass response during high pressure grouting
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The sealing of hard jointed rock by grouting involves several complicated mechanical systems. The result is a complex coupled system of hydro- logical and mechanical precesses. In order to determine the higher order effects of the resulting system the fracture deformations must be assessed. This requires a model that mimics the mechanical behaviour of not only fractures under normal load but also the entire rock mass system. This model indicates that there are two dominant regimes involved; a permeation regime and a high pressure regime. The pressure limit that separates permeation grouting from high pressure grouting can then be found to be closely related to the in situ stress. In the high pressure regime the deformations may be large but very situation-dependent. The principal deformational eigenmodes of some boundary conditions are considered. The analysis indicates that the usage of high pressure grouting can be both benficial to the operation as well as increase the inflow of water to the excavation.
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| 48. |
- Gustafson, Gunnar, et al.
(författare)
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Stop criteria for cement grouting
- 2005
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Ingår i: Felsbau : Zeitschrift für Geomechanik und Ingenieurgeologie im Bauwesen und Bergbau. - 0174-6979. ; 25:3, s. 62-68
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 49. |
- Gustafson, Gunnar, 1945, et al.
(författare)
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Stop Criteria for Cement Grouting
- 2005
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Ingår i: Felsbau. - 0174-6979. ; 23:3, s. 62-68
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Tidskriftsartikel (refereegranskat)
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| 50. |
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