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  • 1.
    Draganivic, 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)
  • 2.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Bleeding and Filtration of Cement-Based Grout2009Doctoral thesis, monograph (Other academic)
    Abstract [en]

    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.

  • 3.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Separations- och filtreringsstabilitet hos cementbaserat injekteringsbruk2007Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    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.

  • 4.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Separationsstabilitet hos injekteringsbruk2005Report (Other academic)
  • 5.
    Draganovic, Almir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Svällande leror i bergtunnlar - Förstudie2010Report (Other academic)
  • 6.
    Draganovic, Almir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Lagerblad, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Filtration of silica particles from a low-pH cementitious grout2016In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 105, 29-34 p.Article in journal (Refereed)
    Abstract [en]

    Spent nuclear fuel is stored in rock depositories. Swelled bentonite around the stored capsules prevents eventual spread of radioactive material by ground water. The pH-value of the ground water in contact with bentonite shall be less than 11 not to affect the swelling capacity of the bentonite. Therefore cementitious grout with low pH-value is used to grout these depositories. There is a risk that pH-value of this grout can locally increase due to filtration at fracture constriction and influence pH-value of ground water. Chemical SEM EDAX-analysis indicates that there is no risk of increasing of PH-value in this grout.

  • 7.
    Draganovic, Almir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Nejad Ghafar, Ali
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Issues in Measurements and Evaluation of Penetrability of Cement-Based Grout Measured with Filter Pump and Penetrability Meter in the Field2017In: Grouting 2017, American Society of Civil Engineers (ASCE), 2017, Vol. 2, no 288 GSP, 404-414 p.Conference paper (Refereed)
    Abstract [en]

    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.

  • 8.
    Draganovic, 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, 101-112 p.Article 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.

  • 9.
    Draganovic, 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)
  • 10.
    Draganovic, 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)
  • 11.
    Draganović, Almir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Björk, Conny
    Improvement of penetrability of cement based grouts by optimization of cement size curve2013In: 7th Nordic Grouting Symposium / [ed] Johan Funehag, Per Tengborg, Rock Engineering Research Foundation , 2013, 159-163 p.Conference paper (Refereed)
  • 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 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, 1681-1690 p.Conference 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.

  • 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, 548-559 p.Article 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.
    Nejad Ghafar, Ali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Ali Akbar, Saman
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Al-Naddaf, Manar
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Uncertainties in Grout Penetrability Measurements; Evaluation and Comparison of Filter pump, Penetrability meter and Short slot2017In: Geotechnical and Geological Engineering, ISSN 0960-3182, E-ISSN 1573-1529Article in journal (Refereed)
    Abstract [en]

    To measure grout penetrability in fractured hard rock, various measuring instruments have been developed over the years. Penetrability meter and Filter pump have been designed to use in both the lab and the field. Short slot has been applicable mainly in the lab due to its complexity. The fact, that these instruments have been built based on different assumptions, limitations, and test conditions, makes their results occasionally in contradict. Deficiency in design of the instruments as well as the methods of evaluating grout penetrability is additionally a basis for uncertainty in results. This study is an experimental effort to determine and thoroughly perceive the nature of the most governing uncertainties in grout penetrability measurements. The test apparatus, procedure, and method used to evaluate the grout penetrability in both Penetrability meter and Filter pump were thus modified. The aim was to control the corresponding uncertainties and make their limitations and test conditions as similar as possible with the ones in Short slot. The results suggested that to obtain a more realistic evaluation of the grout penetrability, measurement should be accomplished at both the high and the low pressures with sufficient grout volume using Short slot. Moreover, application of both Filter pump and Penetrability meter is no longer recommended due to the revealed uncertainties.

  • 15.
    Nejad Ghafar, Ali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    AN EXPERIMENTAL STUDY OF THE INFLUENCE OF DYNAMIC PRESSURE ON IMPROVING GROUT PENETRABILITY2015Report (Other academic)
    Abstract [en]

    In order to increase the sealing efficiency in rock grouting, the fractures should be entirely grouted while the filtration of cement particles is an obstacle. By reducing the filtration, penetrability of grout will be increased resulting in a more reliable grouting. Some of the advantages of controlling filtration are decreas in time, costs and the environmental impacts of the projects. Increase in the safety margins of the projects during both the construction and the operation are also among the benefits of regulating the filtration.

    Use of variable pressure for improving grout penetrability has been studied in both the lab and the field over the years. The focus of the previous investigations was mainly on application of high frequency oscillating pressure using artificial parallel plates without constrictions with openning sizes larger than 100 μm. The mechanism of improvement of grout penetrability was interpreted as reduction in viscosity due to the oscillation in all those studies. The missing parts of the resulted knowledge are the influences of different shapes of the variable pressure and the effects of low frequencies i.e. longer cycle periods to penetrate through micro fractures smaller than 100 μm with constrictions. Moreover, other mechanisms of improvement of grout penetrability might also be more efficient than reduction in viscosity due to the oscillation.

    The focus of this study is therefore to investigat the influence of low frequency instantaneous variable pressure with different peak and rest periods on regulating the filtration. A pneumatic pressure control system has been thus employed using parallel plates with constrictions of 43 and 30 μm. The proposed mechanism of action was change of flow pattern due to the change in pressure and the corresponding velocity. Comparison of results of the variable and the constant pressures revealed the great impact of the examined variable pressure on improving grout penetrability.

  • 16.
    Nejad Ghafar, Ali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Mentesidis, Anastasios
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    An Experimental Approach to the Development of Dynamic Pressure to Improve Grout Spread2016In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 49, no 9, 3709-3721 p.Article in journal (Refereed)
    Abstract [en]

    Dynamic grouting is one of the methods to improve grout spread in rock that have been investigated since 1985. The results were promising, but all tests were performed under noticeable simplifications related to conditions in rock fractures. This study is an experimental approach to improve the grout spread using low-frequency instantaneous variable pressure as a new alternative with better control of filtration. The method is tested through parallel plates with constrictions of 30 and 43 µm under the applied pressures with 4 s/8 s and 2 s/2 s peak/rest periods. The results reveal conclusively the effectiveness of the method and provide a basis for further development of dynamic grouting.

  • 17.
    Nejad Ghafar, Ali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Mentesidis, Anastasios
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Ett nytt sätt att förbättra inträngnigs egenskaperna hos cementbaserat injekteringsbruk med momentant varierande tryck2016In: Bygg & teknik, ISSN 0281-658X, no 1, 17-22 p.Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Ett mycket viktig moment i samband med undermarksbyggande är tätning av konstruktioner för att hindra vatteninflöde eller ett eventuellt läckage av lagrade material i konstruktionen. Sedan mitten på 1980-talet har man på Kungliga tekniska högskolan (KTH) forskat kring injekteringen av sprickor i berg med varierande tryck för att förbättra inträngningsförmågan av cementbaserade bruk. I tidigare studier har man huvudsakligen undersökt effekten av högfrekventa oscillerande tryck på brukets inträngningsförmåga men den uppnådda förbättringen har visat sig vara relativt begränsad. I ett doktorandprojekt på KTH har vi genomfört en experimentell studie för att undersöka påverkan av istället ett lågfrekvent tryck med en momentan tryckförändering på brukets inträngningsförmåga. Resultaten har visat på en betydande förbättring av inträngningsförmågan hos bruket jämfört med injektering med konstant tryck. Projektet har finansierats av Stiftelsen Bergteknisk Forskning (BeFo), Svenska Byggbranschens Utvecklingsfond (SBUF) och Trafikverket.

  • 18.
    Nejad Ghafar, Ali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Hakansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Application of Low-Frequency Rectangular Pressure Impulse in Rock Grouting2017In: Grouting 2017: Grouting, Drilling, and Verification / [ed] Byle, MJ Johnsen, LF Bruce, DA ElMohtar, CS Gazzarrini, P Richards, TD, American Society of Civil Engineers (ASCE), 2017, Vol. 2, no 288, 104-113 p.Conference paper (Refereed)
    Abstract [en]

    In order to sufficiently seal an underground facility in fractured rock, it is essential to obtain adequate grout spread into the surrounding fractures. The grout spread itself depends on parameters, the most significant of which are the filtration tendency and rheological properties. These properties can be affected by the applied pressure. High-frequency oscillating pressure has been shown to improve grout spread by virtue of reducing the grout viscosity. However, this method has not yet been industrialized due to the quick dissipation of the oscillation along a fracture. In a recent investigation, we examined a low-frequency rectangular pressure-impulse using a short slot. The results showed significant improvements in the injected grout volume in comparison to the static pressure results. In this paper, we examine the method in a considerably longer artificial fracture in order to investigate the dissipation of the pressure impulses. The study indicates the potential of the method to improve the grout spread in rock grouting.

  • 19.
    Nejad Ghafar, Ali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Magakis, Konstantinos
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Varying aperture long slot (VALS), a method for studying grout penetrability into fractured hard rock2017In: ASTM geotechnical testing journal, ISSN 0149-6115, E-ISSN 1945-7545, Vol. 40, no 5, 871-882 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents the design, manufacturing, and assembly of a new laboratory apparatus for investigation of grout filtration tendency and penetrability into rock fractures. The method makes it possible to examine grout samples composed of a wide range of cements and additives/ admixtures with different water-to-solid ratios. The apparatus can be used to investigate the influence of different parameters on grout penetrability. Examples of these parameters include the cement particle size/distribution curves/chemical compositions, and the type and ratio of additives/admixtures that provide a variety of setting/hardening times, and rheological and strength properties. The grouting operation into the rock fractures is replicated using an artificial slot with 4-m-long constrictions varying from 230 to 10 μm, and selective inlet and outlet. The apparatus can also accommodate grouting experiments under both static and dynamic pressure conditions up to 1, 500 kPa to study their influence. Illustrative results are also provided.

  • 20.
    Nejad Ghafar, Ali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Pronina, Elizaveta
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Evaluation of the Real Time Grouting Control (RTGC) Theory using an Artificial Fracture with Variable Aperture2018Manuscript (preprint) (Other academic)
    Abstract [en]

    The real time grouting control (RTGC) theory has been developed to monitor the spread of grout in rock fractures. It predicts the extent of the grout spread over time using the grout properties and the applied pressure. Despite extensive work conducted to verify it in both the lab and the field, it has not yet been sufficiently investigated in the lab under geometry conditions similar to a real fracture in rock. This paper presents a novel effort to examine the performance of the RTGC theory in the presence of constrictions by using an artificial fracture, the so-called varying aperture long slot (VALS). The paper compares the predictions of grout propagation with the experimental results. The predictions obtained using a hydraulic aperture, the way that the theory was previously used in the early stages of development, showed relatively good agreement with the experimental results. In predictions obtained using the mean-physical aperture, the way that the theory is currently used in field applications, the results showed considerably faster spread than the experimental results. This suggests that use of the mean-physical aperture does not always give a good approximation of the apertures to employ in predictions using the RTGC theory. Depending on the geometry conditions, the hydraulic aperture might be more realistic.

  • 21. Place, Joachim
    et al.
    Nejad Ghafar, Ali
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Malehmir, Alireza
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    On using the thin fluid-layer approach at ultrasonic frequencies for characterising grout propagation in an artificial fracture2016In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 89, 68-74 p.Article in journal (Refereed)
    Abstract [en]

    We investigate the ultrasonic transport properties of such an idealised fracture whose 100 µm aperture is about 0.02 the wavelength, and filled with various fluids flowing under external forcing. As the artificial fracture is made of two solid and parallel walls separated by a thin fluid layer, we use the thin fluid layer concept to study the compressional (P-) wavefield transmitted across and reflected off the fracture, with no mode-conversion considered. We demonstrate that air and various fluids (water, grouts of varied w/c – water to cement ratio) can be distinguished when injected into the fracture, both at atmospheric pressure or under over-pressure as done in real grouting cases in the field. Then, using an analytical solution, we verify our experimental data and predict the results that can be obtained with a different fracture aperture. Our results illustrate that replicating such ultrasonic measurements both in space and time would allow successfully monitoring the grout propagation within an artificial fracture.

  • 22.
    Shimizu, H
    et al.
    Tohoku University.
    Koyama, T
    Kyoto University.
    Draganovic, Almir
    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.
    CFD-DEM simulation for filtration and penetrability of cement-based grout2012Conference paper (Refereed)
    Abstract [en]

     Grouting is a widely used method for sealing fractured rock masses around underground structures to reduce or stop groundwater inflow. However, even at pre-sent, the filtration and penetration mechanism of cement-based grout have not been clarified sufficiently yet due to complicated physical and chemical processes of grout, such as pressure-dehydration, consolidation, bleeding, clogging, absorption, sedimen-tation and condensation etc. In this research, to better understand the penetration and filtration mechanism of cement-based grout through rock fractures, a two-dimensional numerical model of coupled Computational Fluid Dynamics and the Distinct Element Method (CFD-DEM) had been developed. By using a direct numerical simulation technique, the interaction between fluid and particles can be evaluated. The simulation results were compared with the laboratory injection test to verify the applicability of the newly developed CFD-DEM code. As a result, the simulation results agree qualitatively well with the actual experi-mental results, and the clogging process during the injection of cement-based grout was successfully reproduced by the CFD-DEM code. Moreover, based on these re-sults, the influence of the water/cement ratio of grout on the filtration and penetration mechanism was investigated in detail. The presented numerical model in this paper gives a better understanding for filtration and penetration mechanism of cement-based grout.

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