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Rheology of cement grout : Ultrasound based in-line measurement technique and grouting design parameters
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. (Grouting)ORCID iD: 0000-0003-1667-8919
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Grouting is performed in order to decrease the permeability and increase the stiffness of the material, especially soil and rock. For tunnelling and underground constructions, permeation grouting is done where cement based materials are pumped inside drilled boreholes under a constant pressure, higher than the ground water pressure. The aim of permeation grouting is to reduce the water flow into tunnels and caverns and to limit the lowering of the surrounding groundwater table. Cement based materials are commonly used as grout due to their availability and lower costs. To obtain a proper water sealing and reduce the lowering of the ground water table, a desired spread of grout must be achieved and the rheology of the cement grout is the governing factor for estimating the required spread. Rheological properties of cement grout such as viscosity and yield stress are commonly measured off-line using laboratory instruments, and some simple tools are available to make field measurements. Although the rheological properties of the grout that is used play a fundamental role in design and execution, no method has yet been developed to measure these properties in-line in field work. In addition to the real time measurement, there is no standard method for determining the yield stress for grouting applications. Despite the common usage of Bingham model fitting to determine the yield stress, the range of shear rate is often not specified or is neglected.

 

In this work, an in-line rheometry method combining the Ultrasound Velocity Profiling (UVP) technique with Pressure Difference (PD) measurements, known as “UVP+PD”, was successfully tested for continuous in-line measurements of concentrated micro cement based grouts. A major obstacle of using the ultrasound based methodology was the transducers, which would be capable of emitting sufficient acoustic energy and can be used in field conditions. The transducer technology was developed in a parallel project and the Flow-Viz industrial rheometer was found to be capable of detail measurement of the velocity profiles of cement grout. The shape of the velocity profiles was visualized, and the change in the shape of the profiles with concentration and time was observed. The viscosity and yield stress of the grout were determined using rheological models, e.g. Bingham and Herschel-Bulkley. In addition, rheological properties were determined using the non-model approach (gradient method) and the tube viscometry concept and were compared with results obtained using the rheological models. The UVP+PD method was found to be capable of determining the rheological behavior of cement grout regardless of the rheological model.

The yield stress of cement grout was investigated using off-line rheometry techniques and UVP+PD in-line measurements. Tests were performed applying different shear histories and it was found that two ranges of yield stress indeed exist. Therefore, the design value of yield stress should be chosen with respect to the prevailing shear rate at the grout front for the required spread of grout. In addition, an appropriate shear rate range should be used when a Bingham fitting is done to determine the yield stress. In order to estimate the shear rate, plug thickness and velocity for one dimensional and two dimensional geometry, a non- dimensional nomogram was developed. The advantage of using the nomogram is that it does not depend on the applied pressure and the rheological properties of the grout and can therefore, be used as a simple design tool. Analytical approaches were used for the estimation and good agreements were found with numerical calculations and experimental results.

In conclusion, in this work, it was found that it is possible to continuously measure the velocity profiles and determine the change of the rheological properties of cement grout using the ultrasound based UVP+PD method under field conditions. The yield stress was also investigated and it was found that two range of yield stress exist depending on the prevailing shear rate of the grout, which should be used for designing the grouting time at different conditions. In order to decide the design value of yield stress for grouting applications, a non-dimensional nomogram was developed that can be used to estimate the plug thickness, shear rate and velocity of the grout. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , xvi, 73 p.
Series
TRITA-JOB PHD, ISSN 1650-9501 ; 1021
Keyword [en]
grouting, grouting design, cement grout, Bingham number, shear rate, plug flow, thixotropy, yield stress, in-line rheology, UVP+PD, Flow-Viz, viscosity bifurcation, aging, off-line rheometry, pump characteristics
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
URN: urn:nbn:se:kth:diva-176885OAI: oai:DiVA.org:kth-176885DiVA: diva2:868713
Public defence
2015-11-18, F3, Lindstedtsvägen 26, KTH Royal Institute of Technology, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

Funding for the project was provided by the Swedish Rock Engineering Research Foundation (BeFo), The Swedish Research Council (FORMAS) and The Development Fund of the Swedish Construction Industry (SBUF), who are gratefully acknowledged. QC 20151112

Available from: 2015-11-12 Created: 2015-11-11 Last updated: 2015-11-12Bibliographically approved
List of papers
1. In-line rheometry of micro cement based grouts - a promising new industrial application of the ultrasound based uvp plus pd method
Open this publication in new window or tab >>In-line rheometry of micro cement based grouts - a promising new industrial application of the ultrasound based uvp plus pd method
2012 (English)In: Applied Rheology, ISSN 1430-6395, E-ISSN 1617-8106, Vol. 22, no 4, 42783- p.Article in journal (Refereed) Published
Abstract [en]

Measurements of the viscosity of non-Newtonian fluids and suspensions having a solid volume fraction of about 30% or more is of major interest from an industrial point of view. Cement paste and cement grouts for injection grouting applications, with water to cement ratios typically in the range of 0.4 and 0.6 - 0.8 by weight, are two examples of industrial fluid systems. Few in-line techniques are available on the market that can be used for these fluid systems and under realistic field conditions. The so-called UVP+PD in-line rheometry method combining the Ultrasound Velocity Profiling (UVP) technique with Pressure Difference (PD) measurements is a promising new tool for industrial applications. This paper presents an initial pre-study that aims to demonstrate the feasibility of the UVP+PD method using cement grouts for process monitoring and control of grouting applications under realistic field conditions. The UVP+PD method was tested and found successful for continuous inline measurements of concentrated micro cement-based grouts with water/cement ratios of 0.6 and 0.8. The test set-up consisted of a combination of an experimental " flow loop" and a conventional field grouting rig - UNIGROUT, from Atlas Copco. The rheological properties were determined, directly in-line and the parameters obtained were subsequently compared with off-line measurements using a conventional rotational rheometer.

Keyword
Cement-based grouts, Flow visualization, In-line rheometry, Permeation grouting, Ultrasound velocity profiling, UVP+PD method
National Category
Civil Engineering Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-105430 (URN)10.3933/ApplRheol-22-42783 (DOI)000310494400009 ()2-s2.0-84867344378 (Scopus ID)
Note

QC 20121122

Available from: 2012-11-22 Created: 2012-11-21 Last updated: 2017-12-07Bibliographically approved
2. In-line rheological measurements of cement grouts: Effects of water/cement ratio and hydration
Open this publication in new window or tab >>In-line rheological measurements of cement grouts: Effects of water/cement ratio and hydration
2015 (English)In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 45, 34-42 p.Article in journal (Refereed) Published
Abstract [en]

The rheological properties of cement based grouts change with water/cement ratio and time, during the course of hydration. For this reason, it is desirable to be able to measure this change continuously, in-line, with a robust instrument during the entire grouting operation in the field.The rheological properties of commonly used cement grouts were determined using the Ultrasound Velocity Profiling combined with the Pressure Difference (UVP. +. PD) method. A non-model approach was used that directly provides the properties, and the results were compared with the properties obtained using the Bingham and Herschel-Bulkley rheological models. The results show that it is possible to determine the rheological properties, as well as variations with concentration and time, with this method.The UVP. +. PD method has been found to be an effective measuring device for velocity profile visualization, volumetric flow determination and the characteristics of the grout pump used.

Keyword
cement grout, in-line rheology, UVP+PD, grouting, ultrasound velocity profiling, cement rheology, hydration.
National Category
Geotechnical Engineering
Research subject
Järnvägsgruppen - Infrastruktur
Identifiers
urn:nbn:se:kth:diva-122641 (URN)10.1016/j.tust.2014.09.003 (DOI)000347022600004 ()2-s2.0-84907701665 (Scopus ID)
Funder
Swedish Research Council Formas
Note

QC 20150202. Updated from submitted to published.

Available from: 2013-05-24 Created: 2013-05-24 Last updated: 2017-12-06Bibliographically approved
3. Yield stress of cement grouts
Open this publication in new window or tab >>Yield stress of cement grouts
(English)Manuscript (preprint) (Other academic)
Abstract [en]

: The rheology of cement grout is complex due to its thixotropic nature and the presence of a yield stress. Despite the importance of the yield stress for grouting design, no standard methods are yet available to determine the yield stress. Most common methods are based on using conventional rheometers, but the results are subjective due to the measurement techniques, applied shear history and hydration. In this work, measurement of the yield stress of cement grout was performed with different measurement techniques using a conventional rheometer. In addition, in-line measurements using an ultrasound based technique were made in order to visualize the flow profile and perform a direct measurement of the yield stress. Two ranges of yield stress, static and dynamic yield stress, were measured. These results should be used for design purposes depending on the prevailing shear rate. The ultrasound based Flow Viz industrial rheometer was found capable of performing direct in-line measurement of the yield stress and providing a detailed visualization of the velocity profile of cement grout.

Keyword
yield stress, thixotropy, grouting, cement grout, in-line rheology, UVP+PD, ultrasound velocity profiling
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-176886 (URN)
Note

The authors wish to acknowledge the financial support from the Swedish Rock Engineering Research Foundation (BeFo) and the Swedish Construction Industry Development Fund (SBUF). 

QS 2015

Available from: 2015-11-11 Created: 2015-11-11 Last updated: 2015-11-12Bibliographically approved
4. Cement grouting design: a nomogram for velocity, plug thickness and shear rate
Open this publication in new window or tab >>Cement grouting design: a nomogram for velocity, plug thickness and shear rate
(English)Manuscript (preprint) (Other academic)
Abstract [en]

 In recent decades, there has been a substantial increase in knowledge of the propagation of cement grout inside rock fractures, assuming the Bingham model. Yield stress is used as an important design parameter in estimating grout penetration and maximum penetration length. Due to the thixotropic nature of cement grouts, the yield stress depends on the shear history and shear rate present during propagation. Although analytical solutions for velocity, plug thickness and shear rate are available for one-dimensional geometries, a different approach must be used for two-dimensional radial Bingham fluid flow. This is due to the non-linear pressure and velocity distribution leading to a change of the plug thickness along the radial distance. In this work, an analytical approach is provided for the determination of the velocity, plug thickness and shear rate for a two-dimensional (2D) radial Bingham flow between parallel disks. The results were compared with rectilinear flow in a one-dimensional (1D) circular pipe and rectangular channel. In addition, numerical calculations and experimental tests were used to validate the results. A non-dimensional nomogram was also developed in order to facilitate the design of the grouting time with respect to velocity, plug thickness and shear rate. The relevant design parameters can be obtained from the nomogram for the corresponding relative spread of the grout, and it can therefore be used as a simple design tool for cement grouting.

Keyword
grouting, grouting design, cement grout, Bingham number, shear rate, plug flow, thixotropy, yield stress
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-176887 (URN)
Note

The authors wish to acknowledge the financial support from the Swedish Rock Engineering Research Foundation (BeFo) and the Swedish Construction Industry Development Fund (SBUF). The experimental test using the fracture replica was performed at the Division of Geo Engineering, Chalmers University of Technology and gratefully acknowledged. QS 2015

Available from: 2015-11-11 Created: 2015-11-11 Last updated: 2015-11-12Bibliographically approved
5. Grout pump characteristics evaluated with the UVP+PD method
Open this publication in new window or tab >>Grout pump characteristics evaluated with the UVP+PD method
2012 (English)In: IRSM International Symposium, EUROROCK 2012, Stockholm, 2012, 1-14 p.Conference paper, Published paper (Refereed)
Abstract [en]

Rock grouting is performed to decrease the hydraulic conductivity around underground structures, such as tunnels and caverns. Cement grouts are often used and pumped into joint and fractures of the rock formation.

Piston type pumps are mostly used for high pressure rock grouting. A pulsation effect is inevitable when using this type of pump due to the movement of the piston. The effect of this pulsation on rock grouting is yet to be known but believed to be benefi-cial for the penetration of the grout. Current flow meters used in the field are not accu-rate enough to determine the fluctuation of the flow rate when it is less than 1 l/min. In addition, currently available flow meters measure the average of the flow over a cer-tain period of time, hence the true fluctuation of the flow rate due to the pulsation of the piston remains unknown.

In this paper, a new methodology, the so called ‘Ultrasound Velocity Profiling – Pressure Difference’ (UVP+PD) method has been introduced to show the pulsation effect when using a piston type pump. The feasibility of this method was successfully investigated for the direct in-line determination of the rheological properties of micro cement based grouts under field conditions (Rahman & Håkansson, 2011). Subse-quently, it was also found that this method can be very efficient to measure the fluctu-ation of the flow rate for different types of pumps.

From a grouting point of view the UVP+PD method can be used to synchronize the pressure and flow of a piston type pump by measuring the pulsation effect. Conse-quently it can be used as a tool for the efficiency and quality control of different types of pumps.

Keyword
cement grouts, pump characterization, grouting, ultrasound velocity, profiling, UVP+PD
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-107161 (URN)
Conference
IRSM International Symposium, EUROROCK 2012, 28-30 May, Stockholm
Note

QC 20121221

Available from: 2012-12-21 Created: 2012-12-06 Last updated: 2015-11-12Bibliographically approved

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