| 1. |
- Funehag, Johan, 1975, et al.
(författare)
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How the Pressure Build-Up Affects the Penetration Length of Grout-New Formulation of Radial Flow of Grout Incorporating Variable Pressure
- 2017
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Ingår i: Geotechnical Special Publication. - Reston, VA : American Society of Civil Engineers. - 0895-0563. - 9780784480793 ; 0:288, s. 143-151
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Konferensbidrag (refereegranskat)abstract
- For around two decades of research and development in the field of grouting in hard jointed rock, the design process has taken some leaps forward. Stille and Gustafson, 2005 and Funehag and Gustafson 2008, shows how a grouting design can be computed. A grouting design in hard rock can based on the penetration length of grout in rock fractures. The design comprises considerations of the fracture apertures in the rock mass, the type of grout and its rheological properties and how the grout is injected i.e pressure and grouting times. When knowing these parameters an optimized geometry fitting the design is made. Thörn, et al, 2014 describes a fundamental analysis with a comprehensive tool to retrieve the fracture distribution and aperture distribution of the fractures crossing a cored borehole. The data needed about the core is geological mapping and hydraulic section tests. In Gustafson, Claesson and Fransson, (2013) a full derivation of a radial Bingham flow in a slit is described for constant pressure. By optimizing with a specific pressure and an efficient grouting time (efficient time means the time when the pressure has reached the designed pressure) a prognosis a more realistic time consumption for grouting can be computed. However, the time it takes to reach a certain pressure is dependent on the capacity of the pump and the how large the fractures widths are. For poorly chosen pumps together with large fractures the time to reach the design pressure can be significant. The overall objective for this new formulation was to involve the grouting pressure as a variable rather than constant. A pressure build-up mimic more a realistic pumping scenario which enables better prognosis of grouting works. This paper brings up this new formulation of the radial Bingham flow with variable injection pressure in slit. The benefits of this new formulation is that it can easily be integrated in other computer programs. One program that uses this new formulation is a grouting simulator owned and developed by Edvirt AB. The simulator has been used to pedagogically demonstrate how a variable pressure and restrictions in grout flow (the pump capacity) affect the penetration length. Further, the results show that it can be used to predict suitable pump capacity to fit the coming grouting works.
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| 2. |
- Al-Naqshabandy, Mohammed Salim, et al.
(författare)
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Effect of spatial variability of the strength properties in lime-cement columns on embankment stability
- 2012
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Ingår i: Geotechnical Special Publication. - Reston, VA : American Society of Civil Engineers. - 0895-0563. ; 228, s. 231-242
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Tidskriftsartikel (refereegranskat)abstract
- Spatial variability with respect to the strength in lime-cement columns is an unavoidable source of uncertainty that should be considered in design. Current design method for the assessment of embankment stability, based on the deterministic factor of safety, cannot address the effect of spatial variability. Reliability-based design methodology is a powerful tool that can be used to integrate the variability into the analysis. In this paper, the spatial variability with respect to the undrained shear strength in the soil and in the columns was evaluated based on CPT test. The first order second moment (FOSM) reliability method was applied to address the impact of the spatial variability of the strength in the soil and in the columns on the reliability of an embankment founded on improved soil by lime-cement columns. The paper also presents a technique to evaluate the variance reduction factor over the failure surface. The results propose that the undrained shear strength in the soil and in the columns can be modelled following normal or lognormal distribution. The analysed example show that the reliability increased significantly when the spatial variability was considered
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| 3. |
- Axelsson, Morgan, et al.
(författare)
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Column penetration tests for lime-cement columns in deep mixing - experiences in Sweden
- 2003
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Ingår i: Geotechnical Special Publication. - 0895-0563. ; 120, s. 681-694
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Tidskriftsartikel (refereegranskat)abstract
- In this paper column penetration tests for lime-cement columns in deep soil mixing are reviewed. In principle, column penetration tests and reversed column penetration tests are considered. Improved test techniques are presented and discussed based on tests from two test sites in Sweden. The investigations indicate that the reversed column penetration test is the most suitable method for the primary quality test with reference to the uniformity and continuity of the columns. The probe should, however, be installed by the lime-cement column machine short after the manufacturing of the column to avoid disturbances in the mixing process and to enable a random test selection.
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| 4. |
- Bjureland, William, et al.
(författare)
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Challenges in applying fixed partial factors to rock engineering design
- 2017
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Ingår i: Geotechnical Special Publication. - Reston : American Society of Civil Engineers (ASCE). - 0895-0563. ; :283, s. 384-393
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Tidskriftsartikel (refereegranskat)abstract
- The Swedish national guidelines for design of the main structural support system in road and railway rock tunnels have been adjusted to cohere with Eurocode 7. In the design guidelines, the limit states that the designer should consider are specified. The main method to account for uncertainties in the Swedish guidelines is similar to the method preferred in Eurocode 7: the partial factor method. For each limit state, fixed partial factors retrieved from different sections of the Eurocodes are specified. However, fixed partial factors may not correspond to the same structural reliability for all design situations. In this paper, we show for a common design situation in rock engineering design how partial factors in theory should vary with design geometries and uncertainties. The derived partial factors are compared to the Eurocodes’ fixed values. We find that using fixed partial factors to ensure structural safety in these limit states might not be suitable. The implications are discussed along with suggestions of other more suitable methods to account for uncertainties in rock engineering design.
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| 5. |
- Butron, Christian, 1978, et al.
(författare)
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A Swedish grouting design concept: Grouting with silica sol in the Nygård and Törnskog tunnels
- 2012
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Ingår i: Geotechnical Special Publication. - Reston, VA : American Society of Civil Engineers. - 0895-0563. - 9780784412350 ; :228 GSP, s. 826-835
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Konferensbidrag (refereegranskat)abstract
- The scope of this paper is to present two tunnel grouting design case studies where the waterproofing aimed not only to reduce the water inflow to a specified level, but to minimize the number of dripping spots by means of pre-excavation grouting. Every grouted section of around one hundred meters in both tunnels used relevant parameters from the rock and the grout material properties to develop an adequate, pre-excavation grouting design. Both tunnels, constructed in crystalline rock, used silica sol as the main grouting material and were evaluated later by means of control boreholes and dripping characterization. Control boreholes showed a decrease in the transmissivity in these sections, and the dripping characterization showed a reduction in the number of dripping spots compared to the rest of the tunnel, where this pre-excavation grouting concept was not used. This led to minimization of the number of drains used, which was clearly visible in the Nygård case, suggesting that the designs were successful and confirming that an understanding of the rock and grout properties is crucial to the design concept.
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| 6. |
- Draganović, Almir, 1964-, et al.
(författare)
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Issues in Measurements and Evaluation of Penetrability of Cement-Based Grout Measured with Filter Pump and Penetrability Meter in the Field
- 2017
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Ingår i: Grouting 2017. - Reston, VA : American Society of Civil Engineers (ASCE). - 9780784480793 ; , s. 404-414
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Konferensbidrag (refereegranskat)abstract
- Grouting of underground constructions is important to decrease water inflow into constructions. It is therefore important to use grout with good penetration ability to achieve this goal. The purpose of this paper is to show issues connected to measuring of the penetration ability of cement-based grouts in the field with a filter pump and penetrability meter and show the need for improvement or use of some other method. Three main reasons which contribute to a different estimated critical aperture with these two methods are: different maximum test volume in regression analysis of measured data, limited maximum test volume in the filter pump, and different test pressure. Test volume should be related to volume of designed grout spread in the critical aperture and test pressure should be related to grout spread velocity in the field.
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| 7. |
- Fransson, Åsa, 1971, et al.
(författare)
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A swedish grouting design concept: Hydraulic testing and selection of grout
- 2012
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Ingår i: Geotechnical Special Publication. - Reston, VA : American Society of Civil Engineers. - 0895-0563. - 9780784412350 ; :228 GSP, s. 1691-1700
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Konferensbidrag (refereegranskat)abstract
- Some grouting boreholes take no grout and some boreholes take too much, two extremes related to grouting technique, grout properties and the properties of fractures intersecting the boreholes. Successful sealing of rock and soil demands an adequate description of the system to be grouted as a basis for grouting design and selection of grouting material. The basis for this Swedish concept of grouting design is the individual fractures and the hydraulic apertures, b, of these fractures. The hydraulic aperture is an important parameter to describe the grouting behavior and is used to determine if the grout can enter the fractures, the penetrability. The hydraulic aperture also determines the penetration length in addition to grout parameters e.g. yield stress, τ0, and viscosity, μg as well as grouting pressure and time. Knowing these parameters, a proper grouting technique can be adapted. Important input for both design and performance are simple and practical tests of rock and grout and the intention of this paper is to present a testing procedure and give examples from laboratory and field experiences that the approach actually works. © 2012 American Society of Civil Engineers.
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| 8. |
- Funehag, Johan, 1975, et al.
(författare)
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New frontier in post-grouting of tunnels in hard rock
- 2012
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Ingår i: Geotechnical Special Publication. - Reston, VA : American Society of Civil Engineers. - 0895-0563. - 9780784412350 ; :228 GSP, s. 846-856
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Konferensbidrag (refereegranskat)abstract
- Post-grouting is a difficult task. It is often coupled with high costs and a result that is difficult to quantify. An infrastructure tunnel in an urban city in southern Sweden was used to develop and implement design methodology for post-grouting. The water inflow measured in weirs prior to post-grouting was about 3.8 l/min/100 m. The task of sealing low water inflows to achieve even lower ones takes a lot of effort and determination. The tunnel was built in the 1970s using the traditional drill-and blast method. During the pre-investigations of the project the analysis showed very good pre-grouting, giving a sealed zone of almost 10 meters. The tunnel had a large, sealed zone with a smaller hydraulic gradient and only narrow fractures were left unsealed. The grout chosen was the newly developed silica sol for the presumed narrow fractures and a robust cement grout if large inflows were hit by the grout holes. The tunnel is small, roughly 12 m2 and heavily congested with cables and heating pipes, making it difficult to use traditional machinery. The tunnel section, 90 m in length, was divided into three different sub-sections, each with specific goals. The result showed that the strategy developed worked well and production was more rapid than presumed. The targeted water inflow rate of 1 l/min was met. © 2012 American Society of Civil Engineers.
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| 9. |
- Hernqvist, Lisa, 1968, et al.
(författare)
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A Swedish Grouting Design Concept: Decision Method for Hard Rock Tunneling
- 2012
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Ingår i: Geotechnical Special Publication. - Reston, VA : American Society of Civil Engineers. - 0895-0563. - 9780784412350 ; :228 GSP, s. 816-825
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Konferensbidrag (refereegranskat)abstract
- Efficient grouting of hard rock requires adequate knowledge of the water-bearing fracture system in the rock mass. The observational method approach involves identifying different possible scenarios and relating them to predefined strategies for grouting design. Parameters useful in preparing a relevant description of the rock mass are presented, as well as a method for choosing a conceptual model. The implications of different fracture systems for the grouting design are discussed. A method is presented for deciding whether grouting is needed in order to ensure a high degree of probability that tunnel leakage will remain below the inflow requirements. The methods presented are applied to data from a real tunnel to illustrate the procedures.
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| 10. |
- Håkansson, Ulf, et al.
(författare)
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In-Line Determination of Cement-Based Grout Properties Using a Pulsed Ultrasound Based Method and System
- 2017
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Ingår i: Geotechnical Special Publication. - Reston, VA : American Society of Civil Engineers. ; , s. 356-367, s. 356-367
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Konferensbidrag (refereegranskat)abstract
- In construction, grouting is used to improve or alter the natural properties of soil or rock by injecting a grout into the pores or fractures of the formation. In order to predict the grout penetration progress and maximum penetration length, modern methods for grouting design involve a detailed knowledge of the rheological properties of the used grout. Today, rheological properties of grouts are measured either in a laboratory with conventional rheometers or in the field with simple devices. Due to the complex flow behavior of cement-based grouts, being non-Newtonian yield stress fluids with history and time dependent rheological properties, the results are non-consistent, device dependent and strongly influenced by the test procedure and operator. No standard measurement method is available for rheological characterization of grouts in the grouting industry today. In order to improve this unfortunate situation a new complete measuring methodology, based on pulsed ultrasound, is proposed. The method has been tested for cement-based grouts, with good results. In this work, a new container-based field laboratory is presented, equipped with the Flow-Viz system, which is designed for in-line measurements of rheological properties of cement-based grouts under field-like conditions. Results obtained under field-like conditions are presented in order to demonstrate the applicability of the new system.
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