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Study of Pumping Pressure and Stop Criteria in Grouting of Rock Fractures
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.ORCID iD: 0000-0002-3556-3562
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Today practice of grouting is based on empirical approaches in that, pumping pressure and stop criteria are determined by benchmarking similar projects. Considering a maximum limit for grouting pressure would allow applying a relatively high pressure that may lead to jacking of the fracture or even uplift of the rock mass. On the other hand, keeping the pressure lower than the overburden, in order to avoid any deformation, will prolong grouting process. Determination of pumping pressure is more complicated considering the induced energy to the rock fracture due to combination of the injected volume and pumping pressure. In other word, pressurizing large volume of the injected grout with a low pumping pressure establish the same force inside the fracture as the high applied grouting pressure on small injected volume do. Therefore, an stop criterion to limit grouting volume along with grouting pressure, which is a hyperbola trimming maximum pressure-maximum volume limits and  named as grout intensity number (GIN), has been defined. However, in using this stop criterion and at completion point, the state of the fracture and the distance that grout spread inside the fracture are unknown. As a theoretical approach, examining the flow of the Bingham fluid in network of fractures led to development of a numerical model and later an analytical solution, which enabled estimation of distance that grout spread in the fractures in real time. Finally, theoretical curves to limit elastic and ultimate jacking were established to limit grout pressure in correlation with depth of grout penetration by considering the state of the fracture.  

Despite empirical and theoretical developments, determination of optimum grouting pressure is still challenging. In this study, In addition to examining performance of the analytical solution in estimation of grout spread and distinguishing onset of fracture jacking, the goal is coming up with recommendations for selection of optimum grouting pressure, by examining mechanism of elastic jacking. For this purpose, negative aspects of fracture deformation, which are increase of grouting time and remaining transmissivity, were quantified and discussed against its positive effect on increase of penetrability. By that, application of a relatively high pressure was recommended in order to opening of the fracture to a permitted level, with purpose of increasing penetrability while considering negative effects of elastic jacking. The stop criterion is defined as the grouting time of achieving the required distance of grout spread at the highest applicable grouting pressure.

In examining empirical methods, in grouting of fractures in deep levels, pressure-depth graph suggests usage of higher pressure in compare with the estimated pressure by theory while GIN method is conservative. In further studies GIN was estimated analytically and applying a relatively high grouting pressure in order to opening the fracture, up to attaining the hyperbola, and continuation of grouting with decreasing trend, in order to bringing the fracture back to its initial size at refusal, were proposed. Complexity of using this methodology in compare with theoretical approach was discussed.

As the future work, there is a need to verify the results in the field, and to confirm well performance of this analytical solution in different geologies. Examining variation of grout mixture properties during grouting program as well as significance of simplification of geological pattern to a single horizontal fracture, in that grout flow radially, are among other future studies that can develop this theoretical application further.  

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , 42 p.
Series
TRITA-JOB PHD, ISSN 1650-9501 ; 1020
Keyword [en]
Rock Mechanics, Grouting
National Category
Geotechnical Engineering
Research subject
Solid Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-155323OAI: oai:DiVA.org:kth-155323DiVA: diva2:760821
Public defence
2014-11-21, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20141106

Available from: 2014-11-06 Created: 2014-11-04 Last updated: 2014-11-06Bibliographically approved
List of papers
1. Applying Real Time Grouting Control Method in Sedimentary Rock
Open this publication in new window or tab >>Applying Real Time Grouting Control Method in Sedimentary Rock
2012 (English)In: Grouting and deep mixing: 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, 1450-1459 p.Conference paper, Published paper (Refereed)
Abstract [en]

We report on preliminary studies of low (14 at.%) and high (53at.%) concentration Mn doped MgO films deposited by co-sputtering from metallic Mn and Mg targets. The structural, surface morphologies and magnetic properties of the films of different thickness were studied. All the as grown films are found to be amorphous and film surfaces are found to be flawless and homogeneous. We observe at room temperature robust ferromagnetic loops with a saturation magnetization value that is a function of film thickness reaching a maximum of ≃38.5 emu/cm3 in the Mn0.53Mg0.47O film at a thickness of ≃92 nm. In thicker films room-temperature ferromagnetic ordering is suppressed and eventually at a thickness around 120nm the expected diamagnetism of the bulk appears. The origin of ferromagnetism may be attributed to cation defects at the Mg-site.

Place, publisher, year, edition, pages
American Society of Civil Engineers (ASCE), 2012
Series
Geotechnical Special Publication, ISSN 0895-0563 ; 228
National Category
Civil Engineering Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-75018 (URN)10.1557/opl.2013.611 (DOI)2-s2.0-84888388845 (Scopus ID)978-078441235-0 (ISBN)
Conference
4th International Conference on Grouting and Deep Mixing, Marriott New Orleans, New Orleans, LA, February 16-18, 2012
Note

QC 20130520

Available from: 2012-02-04 Created: 2012-02-04 Last updated: 2017-01-17Bibliographically approved
2. Control of rock jacking considering spread of grout and grouting pressure
Open this publication in new window or tab >>Control of rock jacking considering spread of grout and grouting pressure
2014 (English)In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 40, 1-15 p.Article in journal (Refereed) Published
Abstract [en]

This paper describes a theoretical approach for monitoring fracture dilatancy (or “jacking”) during grouting. From this, a methodology to optimize the grout pumping pressure has been developed, based on the required penetration length (i.e. the distance that the grout spreads from the grout hole into the network of fractures within the rock mass). Empirical rules are put forward to prevent the damage that may result from uncontrolled deformation (Jacking) of the fractures, by limiting either pumping pressure or the injected grout volume, or by a combination of both. The state of the fractures and the spread of the grout when these limits are reached are discussed. The theoretical approach, which is referred to here as the Real Time Grouting Control Method, enables the estimation of grout penetration length or “spread” in real time. This gives an opportunity to monitor fracture dilation as it happens and, for the purpose of this paper, the allowable limits of elastic deformation and jacking have been estimated based on the grout spread. Two case histories are analyzed, for which the physical reaction of the fracture deformation with time and grout spread are determined from the recorded pressure and flow. By comparing the observed physical reaction with the theories for jacking presented here, the Real Time Grouting Control Method has been validated, and it is shown that this theoretical approach is superior to commonly used empirical methods, in that it allows the optimization of the pumping pressure to achieve a given penetration length in the shortest time and with an acceptable fracture dilatancy. This approach is a major step forward in customizing grouting works.

Keyword
Grouting pressure, Jacking, Penetration length, Grout take
National Category
Civil Engineering Geotechnical Engineering
Research subject
Järnvägsgruppen - Infrastruktur
Identifiers
urn:nbn:se:kth:diva-122410 (URN)10.1016/j.tust.2013.09.005 (DOI)000330150700001 ()2-s2.0-84885795114 (Scopus ID)
Note

QC 20140212

Available from: 2013-05-20 Created: 2013-05-20 Last updated: 2017-12-06Bibliographically approved
3. Basic Mechnism of Elastic Jacking and Impact of Fracture Aperture Change on Grout Spread, Transmissivity and Panetrability
Open this publication in new window or tab >>Basic Mechnism of Elastic Jacking and Impact of Fracture Aperture Change on Grout Spread, Transmissivity and Panetrability
(English)Manuscript (preprint) (Other academic)
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-155456 (URN)
Note

QS 2014

Available from: 2014-11-06 Created: 2014-11-06 Last updated: 2014-11-06Bibliographically approved
4. Applicability of using GIN method, by considering theoretical approach of grouting design
Open this publication in new window or tab >>Applicability of using GIN method, by considering theoretical approach of grouting design
2015 (English)In: Geotechnical and Geological Engineering, ISSN 0960-3182, E-ISSN 1573-1529, Vol. 33, no 6, 1431-1448 p.Article in journal (Refereed) Published
Abstract [en]

In the practice of grouting of fractured rock, currently, empirical methods are used. Amongst them, the GIN method is popular mostly in Europe and has been tried in many projects. The concept of this method is to limit the combination of pressure and injected volume to a specific grout intensity number in order to control the energy induced in the rock fractures and to avoid uplift. However, difficulties in employing this method have been reported, which are mainly due to uncertainties in recognizing the distance of grout penetration and the state of the fractures during grouting and at the completion grouting. In this paper, the purpose has been examining the applicability of the GIN method by defining the characteristic curve of the P·V diagram (referred to here as the hyperbola) and suggesting appropriate completion criteria based on the radius of grout spread around the borehole. This will provide the chance to assign a permitted level of fracture deformation (or jacking) to the GIN by considering the formulation of fracture deformation based on grout propagation in a previously developed theoretical approach by Stille et al. (Geotech Geol Eng 30:603–624, 2012) as a part of the Real Time Grouting Control Method. Thus, in attaining the hyperbola, the identified radius of grout spread is achieved and the resulting fracture deformation at this completion point can be beneficial in improving penetrability. However, if the full extent of this deformation extends beyond the grouted zone, part of the fracture may remain un-grouted, and this will affect the sealing efficiency of the grouting program. This may be continued by selecting a smaller GIN and reducing the grouting pressure as the real time pressure–volume plot moves along the hyperbola, which will bring the fracture back to its initial state as grouting approaches the completion point, i.e. when the grout has spread to the desired distance. This hypothesis has been examined against the grouting works performed in three different real projects, for which the grouting parameters can be determined from the available grouting records. It is concluded that the GIN used in practice was much higher than the theoretically estimated values obtained through the proposed analytical solution. Furthermore, in the grouting of fractures close to the surface, the radius of grout spread impacts the GIN significantly, and only a limited grouting pressure is applicable, thus in using split spacing technique in such circumstances, different GINs should be selected for different sets of boreholes to obtain enough propagation at the maximum applicable pressure. The introduced analytical solution introduced in this paper can be a useful procedure for designing the GIN based on the grout spread. Nevertheless, it becomes complicated in dealing with fracture deformation. In a difficult grouting case where the demand for sealing is high, the recommendation is to use the proposed theoretical approach, which provides detailed information during the actual grouting procedure, by estimation of the radius of grout spread and the state of the fracture in real time

Place, publisher, year, edition, pages
Springer, 2015
Keyword
Fracture deformation, GIN method, Grout spread, Grouting pressure, Stop criteria, Theoretical approach
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-155457 (URN)10.1007/s10706-015-9910-8 (DOI)000364507900004 ()2-s2.0-84946025502 (Scopus ID)
Note

Updated from Manuscript to Article. QC 20160209

Available from: 2014-11-06 Created: 2014-11-06 Last updated: 2017-12-05Bibliographically approved

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Yaghoobi Rafi, Jalaleddin

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