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Zou, L., Håkansson, U. & Cvetkovic, V. (2019). Cement grout propagation in two-dimensional fracture networks: Impact of structure and hydraulic variability. International Journal of Rock Mechanics And Mining Sciences, 115, 1-10
Open this publication in new window or tab >>Cement grout propagation in two-dimensional fracture networks: Impact of structure and hydraulic variability
2019 (English)In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 115, p. 1-10Article in journal (Refereed) Published
Abstract [en]

Analysis of cement grout propagation in water-saturated two-dimensional discrete fracture networks is presented in this study. A two-phase flow model for Bingham fluids flow in a single saturated fracture is extended to simulate cement grouts propagation in saturated networks. Using this extended model, the impacts of network structure and hydraulic variability, i.e., network geometry and aperture distribution, on the propagation process are investigated through numerical simulations. Cement grout propagation in 50 realizations of a two-dimensional discrete fracture network (2D DFN) are simulated with different cases of aperture variability, i.e. constant aperture, uncorrelated and length-correlated heterogeneous apertures following a truncated lognormal distribution. The results indicate that network structure and hydraulic variability significantly affect the grout propagation in 2D DFN systems. The randomized network structure and uncorrelated heterogeneous apertures significantly delay the propagation rate and largely increase the variability range of the propagation volume fraction. In contrast, in the case with length-correlated heterogeneous apertures, the propagation rate increases, while the variability range and rate of change of the propagation volume fraction decreases. The extended two-phase flow model for fracture networks and the simulation results presented in this work are useful for basic understanding of the processes relevant for design, monitoring and execution of rock grouting.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Rock grouting, Bingham fluids, Two-phase flow, Discrete fracture networks, Propagation volume fraction, Uncertainty quantification
National Category
Geophysical Engineering
Identifiers
urn:nbn:se:kth:diva-245902 (URN)10.1016/j.ijrmms.2019.01.004 (DOI)000459008800001 ()2-s2.0-85060117035 (Scopus ID)
Note

QC 20190311

Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-03-11Bibliographically approved
Zou, L., Håkansson, U. & Cvetkovic, V. (2019). Non-Newtonian grout flow in single rough-walled rock fractures. In: : . Paper presented at Münchenbryggeriet i Stockholm 19-20 mars 2019.
Open this publication in new window or tab >>Non-Newtonian grout flow in single rough-walled rock fractures
2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Modeling of cement grout flow in rock fractures plays an important role in the design of rock grouting. Cement grouts used in rock grouting practice are typical non-Newtonian fluids containing yield stress, and are often assumed as Bingham fluids. Natural rock fractures typically consist of rough surfaces. Therefore, in reality, rock grouting process actually involves non-Newtonian fluid flow in rough-walled fractures, which is rarely studied in the literature. In this work, we focus on the impact of surface roughness and present direct numerical simulations of non-Newtonian grouts flow in single rough-walled fractures, using a regularized method to approximate the yield-stress. The rough-walled rock fracture models are created from a laser-scanned surface of a granite rock sample, to represent realistic features of natural rock fractures. The numerical results generally show nonlinear behaviors of non-Newtonian fluid flow in rough-walled fractures. The surface roughness significantly reduces the effective transmissivity when Reynolds number is relatively large. The obtained result can be used for upscaling analysis in practice, in order to reduce the potential uncertainties caused by the surface roughness of the rock fractures.

Abstract [sv]

Modellering av cement-baserade injekteringsmedels strömning i bergsprickor spelar en viktig roll för prediktion och design. De medel som används vid injektering är typiskt icke- Newtonska, med en flytgräns, och antas därför vara av Bingham typ. Naturliga bergsprickor har vanligtvis en rå och ojämn yta. Analyser av injekteringsförlopp borde därför innehålla både icke-Newtonska vätskor och råhet hos sprickorna, vilket oftast inte är fallet i den litteratur som finns tillgänglig idag. I föreliggande arbete fokuseras på inverkan av bergsprickors råhet och numeriska beräkningar redovisas för icke-Newtonska injekteringsmedels strömning i enskilda sprickor, med hjälp av en regulariserad metod för hantering av brukets flytgräns. Sprickytornas råhet modelleras från laser-scannade ytor av granitprover för att erhålla så realistiska förhållanden som möjligt. Resultaten visar på icke-linjära effekter och att de råa sprickytorna har en avgörande inverkan på spricktransmissiviteten och att resultaten kan användas för att minska osäkerheten vid praktisk tillämpning.

Keywords
Rock grouting; cement grout; rough-walled rock fracture; Effective transmissivity
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering; Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-248043 (URN)
Conference
Münchenbryggeriet i Stockholm 19-20 mars 2019
Funder
Rock Engineering Research Foundation (BeFo)
Note

QC 20190412

Available from: 2019-04-02 Created: 2019-04-02 Last updated: 2019-06-11Bibliographically approved
Zou, L., Håkansson, U. & Cvetkovic, V. (2018). Impacts of elastic jacking on rock grouting. In: ISRM International Symposium - 10th Asian Rock Mechanics Symposium, ARMS 2018: . Paper presented at 10th Asian Rock Mechanics Symposium, ARMS 2018, 29 October 2018 through 3 November 2018. International Society for Rock Mechanics
Open this publication in new window or tab >>Impacts of elastic jacking on rock grouting
2018 (English)In: ISRM International Symposium - 10th Asian Rock Mechanics Symposium, ARMS 2018, International Society for Rock Mechanics , 2018Conference paper, Published paper (Refereed)
Abstract [en]

The injection pressure is an important design and operational parameter in rock grouting since it controls the grout penetration length and may cause harmful mechanical deformation of the rock mass, such as opening/dilation of the fractures, referred to as jacking. At present, modeling of rock grouting mainly relies on analytical models where the impact of jacking on the grout penetration in rock fractures is not considered. In this study, we present a hydro-mechanical coupled model for rock grouting in a single one-dimensional rock fracture, with consideration of jacking and two-phase flow, i.e. cement grout and groundwater. It assumes that the cement grouts are Bingham fluids and that the rock matrix is an elastic material. The fracture is simplified as a pair of smooth parallel plates. A finite element method (FEM) code is developed to iteratively solve the two-phase flow in the fracture and the elastic deformation of the rock matrix. Two cases with and without consideration of jacking are simulated and compared. The results generally show that jacking of fractures significantly affects the grout penetration in the fracture, which should be properly considered in modeling of rock grouting. This numerical model is able to describe more realistic physical processes in rock grouting, which can be used to estimate the optimal injection pressure in practice. 

Place, publisher, year, edition, pages
International Society for Rock Mechanics, 2018
Keywords
Bingham Fluids, Jacking, Linear Elasticity, Rock Grouting, Two-phase Flow
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-251776 (URN)2-s2.0-85064260749 (Scopus ID)9789811190032 (ISBN)
Conference
10th Asian Rock Mechanics Symposium, ARMS 2018, 29 October 2018 through 3 November 2018
Note

QC 20190528

Available from: 2019-05-28 Created: 2019-05-28 Last updated: 2019-05-28Bibliographically approved
Zou, L., Håkansson, U. & Cvetkovic, V. (2018). Modeling of rock grouting in saturated variable aperture fractures. In: Proceedings of Bergdagarna 2018.: . Paper presented at Bergdagarna 2018 (pp. 79-87). , Article ID 10.
Open this publication in new window or tab >>Modeling of rock grouting in saturated variable aperture fractures
2018 (English)In: Proceedings of Bergdagarna 2018., 2018, p. 79-87, article id 10Conference paper, Published paper (Refereed)
Abstract [en]

Modeling and analysis of cement grouts flow in rock fractures is important in the design, execution and monitoring of grouting in fractured rocks. At present, modeling of rock grouting mainly relies on analytical models, e.g., the real time grouting control (RTGC) method. In the RTGC method, it is assumed that the rock fractures are consisting of smooth parallel plates or disks and water flow is neglected. However, in reality, the natural rock fractures are commonly consisting of complex rough-walled surfaces and are filled with groundwater; therefore, grouting is actually a multiphase (non-Newtonian grouts and groundwater) flow process in rough-walled rock fractures with variable apertures. In this study, we present an efficient one-dimensional (1D) numerical model for modeling of rock grouting in a single rock fracture with consideration of multiphase flow and variable apertures. It is assumed that the cement grouts are Bingham fluids and that the analytical solution for flowrate with a given pressure gradient in a pair of smooth parallel plates is locally applicable. A time-dependent advection equation is used to describe the interface (between the grout and groundwater) propagation. A finite element method (FEM) code is developed to iteratively solve the mass balance and the interface advection equations. The numerical simulations are compared with the RTGC method. It generally shows that water flow significantly affect grouts penetration in the fracture, especially for the grouts with relatively lower viscosity. The variable aperture significantly postpones the penetration process compared with that of constant aperture. This numerical model is able to describe more realistic physical processes and geometry conditions in rock grouting, which can be readily used in practice to reduce the potential uncertainties in application of simplified analytical models.

Abstract [sv]

Modellering och analys av cementbaserade injekteringsmedels strömning är viktiga hjälpmedel för design, utförande och uppföljning av injektering i sprickigt berg. Dagens modeller är ofta baserade på förenklade analytiska lösningar, exempelvis de som ingår i ”Real time grouting control (RTGC)” metoden. För att analytiska lösningar skall kunna användas, antas att sprickorna utgörs av släta, plan-parallella skivor och att dessa inte innehåller något vatten. I verkligheten är dock sprickorna råa, vattenfyllda och med komplexa geometrier, vilket medför att cementinjektering i sprickigt berg i strikt mening är en multi-fas process i en varierande geometri. I föreliggande studie, presenteras en en-dimesionell numerisk model för injektering i en enskild spricka, under beaktande av multi-fas strömning med varierande spricköppning. En tidsberoende advektionsfunktion används för att beskriva gränsskiktet mellan injekteringsmedel och vatten och dess förflyttning med tiden. Resultaten visar på en betydande påverkan från sprickornas vatteninnehåll, dels på tryckfördelningen men även på injekteringsmedlets inträngning i sprickorna, särskilt vid låg viskositet. Den varierande spricköppningen gör också att inträngningen blir långsammare i förhållande till fallet med en konstant spricköppning, vilket är förväntat. Den numeriska modellen beskriver förhållandena på ett mer realistiskt sätt, både ur fysikalisk och geometrisk synvinkel, vilket kan utnyttjas i praktiken för att reducera potentiella osäkerheter vid användandet av dagens analytiska metoder.

National Category
Infrastructure Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-226885 (URN)
Conference
Bergdagarna 2018
Funder
Rock Engineering Research Foundation (BeFo)
Note

QC 20180515

Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2018-05-15Bibliographically approved
Zou, L., Håkansson, U. & Cvetkovic, V. (2018). Two-phase cement grout propagation in homogeneous water-saturated rock fractures. International Journal of Rock Mechanics And Mining Sciences, 106, 243-249
Open this publication in new window or tab >>Two-phase cement grout propagation in homogeneous water-saturated rock fractures
2018 (English)In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 106, p. 243-249Article in journal (Refereed) Published
Abstract [en]

Modeling of cement grout flow in rock fractures is important for the design, monitoring and execution of rock grouting that is widely used in a variety of rock engineering applications. This study presents a mathematical model based on the Reynolds flow equation for cement grout flow in a homogeneous water-saturated rock fracture. The model is based on two-phase flow, i.e. grout as a Bingham fluid and groundwater as a Newtonian fluid, and is used for investigating the importance of the water phase in rock grouting. The modeling results for the two-phase flow generally show the importance of the water phase that can significantly affect the pressure distribution and grout penetration in the fracture, especially under the condition of grout hardening. Such effects depend on the viscosity ratio between the grout and groundwater, which becomes increasingly important for cases with smaller values of the viscosity ratio. The grout density also affects the grout penetration length. Applying an analytical solution based on single-phase flow, i.e. neglecting the impact of groundwater flow, for modeling grout injection, will generally overestimate the penetration length.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keywords
Rock grouting, Bingham fluids, Two-phase flow, Viscosity ratio, Reynolds equation
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-231211 (URN)10.1016/j.ijrmms.2018.04.017 (DOI)000433253600024 ()2-s2.0-85046369617 (Scopus ID)
Note

QC 20180628

Available from: 2018-06-28 Created: 2018-06-28 Last updated: 2018-06-28Bibliographically approved
Zou, L., Jing, L. & Cvetkovic, V. (2017). Effect of sorption on solute transport in a single rough rock fracture. In: 13th ISRM International Congress of Rock Mechanics: . Paper presented at 13th ISRM International Congress of Rock Mechanics 2015, 10 May 2015 through 13 May 2015. International Society for Rock Mechanics
Open this publication in new window or tab >>Effect of sorption on solute transport in a single rough rock fracture
2017 (English)In: 13th ISRM International Congress of Rock Mechanics, International Society for Rock Mechanics , 2017Conference paper, Published paper (Refereed)
Abstract [en]

Sorption process plays a significant role for solute retardation in rock fractures. In this paper, for the aim to investigate the effect of sorption on solute transport in a single rough fracture, a 2D model of representative single rock fracture was built and its roughness was statistically characterized based on the measured data of rock surface topography by laser scanning. A Finite Volume Method (FVM) code was developed to solve the Navier-Stokes (NS) equations and transport equation for numerical modelling the process of fluid flow and solute transport in the rock fracture model. Two groups of simulations were conducted: with and without the consideration of the sorption process with different average flow velocities. The results show that the surface roughness increased the complexities of flow fields, and the non-linear sorption process plays a significant role in the retardation of solute transport through rock fractures. The sorption process caused an obvious lagging time in both the solute concentration fields (plumes) and corresponding breakthrough curves. This lagging time increases with the distance from the inlet boundary, and relatively decreases with the increase of mean velocities.

Place, publisher, year, edition, pages
International Society for Rock Mechanics, 2017
Keywords
Non-linear fluid flow, Rock fractures, Solute transport, Sorption, Surface roughness, Finite volume method, Flow of fluids, Fracture, Navier Stokes equations, Numerical methods, Rock mechanics, Rocks, Surface topography, Break through curve, Non-linear fluids, Rough fractures, Solute concentration fields, Solute retardation, Sorption process, Transport equation, Transport properties
National Category
Geophysical Engineering
Identifiers
urn:nbn:se:kth:diva-227832 (URN)2-s2.0-85044146675 (Scopus ID)9781926872254 (ISBN)
Conference
13th ISRM International Congress of Rock Mechanics 2015, 10 May 2015 through 13 May 2015
Note

QC 20180517

Available from: 2018-05-17 Created: 2018-05-17 Last updated: 2018-05-17Bibliographically approved
Zou, L., Jing, L. & Cvetkovic, V. (2017). Modeling of Solute Transport in a 3D Rough-Walled Fracture-Matrix System. Transport in Porous Media, 116(3), 1005-1029
Open this publication in new window or tab >>Modeling of Solute Transport in a 3D Rough-Walled Fracture-Matrix System
2017 (English)In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 116, no 3, p. 1005-1029Article in journal (Refereed) Published
Abstract [en]

Fluid flow and solute transport in a 3D rough-walled fracture-matrix system were simulated by directly solving the Navier-Stokes equations for fracture flow and solving the transport equation for the whole domain of fracture and matrix with considering matrix diffusion. The rough-walled fracture-matrix model was built from laser-scanned surface tomography of a real rock sample, by considering realistic features of surfaces roughness and asperity contacts. The numerical modeling results were compared with both analytical solutions based on simplified fracture surface geometry and numerical results by particle tracking based on the Reynolds equation. The aim is to investigate impacts of surface roughness on solute transport in natural fracture-matrix systems and to quantify the uncertainties in application of simplified models. The results show that fracture surface roughness significantly increases heterogeneity of velocity field in the rough-walled fractures, which consequently cause complex transport behavior, especially the dispersive distributions of solute concentration in the fracture and complex concentration profiles in the matrix. Such complex transport behaviors caused by surface roughness are important sources of uncertainty that needs to be considered for modeling of solute transport processes in fractured rocks. The presented direct numerical simulations of fluid flow and solute transport serve as efficient numerical experiments that provide reliable results for the analysis of effective transmissivity as well as effective dispersion coefficient in rough-walled fracture-matrix systems. Such analysis is helpful in model verifications, uncertainty quantifications and design of laboratorial experiments.

Place, publisher, year, edition, pages
SPRINGER, 2017
Keywords
Solute transport, Fracture surface roughness, Fracture-matrix system, Matrix diffusion, Contact spots
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:kth:diva-205127 (URN)10.1007/s11242-016-0810-z (DOI)000394425200002 ()
Note

QC 20170620

Available from: 2017-06-20 Created: 2017-06-20 Last updated: 2017-06-20Bibliographically approved
Zou, L., Jing, L. & Cvetkovic, V. (2017). Shear-enhanced nonlinear flow in rough-walled rock fractures. International Journal of Rock Mechanics And Mining Sciences, 97, 33-45
Open this publication in new window or tab >>Shear-enhanced nonlinear flow in rough-walled rock fractures
2017 (English)In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 97, p. 33-45Article in journal (Refereed) Published
Abstract [en]

Nonlinear flow in 3D rough-walled rock fractures is simulated by solving the Navier-Stokes equations. The emphasis is on the impact of shear-caused aperture changes (variable apertures and asperity contacts) and flow conditions (inertial term) upon nonlinear flow behavior. In order to compare shear effects, two 3D fracture models, with and without shear, were established with identical initial rough-walled surfaces topographies of a realistic rock sample. Five groups of simulations with different inflow boundary conditions of flowrates/Reynolds numbers (Re) were conducted to demonstrate shear-enhanced nonlinearity of flow fields and limitations of local cubic law (LCL) approach. The flow results clearly show channeling flow along the preferential paths, transverse flow around the contact spots, and eddy flows behind contact spots with increasing Re, which cannot be observed in 2D models. The effective transmissivity of the 3D fracture model was calculated from the modeling results of velocity and pressure fields. The results showed that the effective transmissivity is a function of local apertures with important uncertainties even when Re is small (i.e. Re = 0.4 in this study), thus the validity of the transmissivity evaluation using LCL approach for nonlinear flow in 3D rough-walled rock fractures is questionable.

Place, publisher, year, edition, pages
Elsevier Ltd, 2017
Keywords
Contact spots, Eddy flow, Effective transmissivity, Nonlinear fracture flow, Rough-walled rock fractures, Shear, Flow fields, Fracture, Navier Stokes equations, Nonlinear equations, Rocks, Shearing, Fracture flow, Rock fractures, Transmissivity, Shear flow, boundary condition, eddy, fracture aperture, Navier-Stokes equations, nonlinearity, Reynolds number, rock mechanics, three-dimensional modeling
National Category
Geophysical Engineering
Identifiers
urn:nbn:se:kth:diva-218825 (URN)10.1016/j.ijrmms.2017.06.001 (DOI)2-s2.0-85020782537 (Scopus ID)
Note

QC 20180117

Available from: 2018-01-17 Created: 2018-01-17 Last updated: 2018-01-17Bibliographically approved
Rasul, H., Zou, L. & Olofsson, B. Monitoring of moisture and salinity content in an operational road structure by electrical resistivity tomography.. Near Surface Geophysics
Open this publication in new window or tab >>Monitoring of moisture and salinity content in an operational road structure by electrical resistivity tomography.
(English)In: Near Surface Geophysics, ISSN 1569-4445, E-ISSN 1873-0604Article in journal (Refereed) Accepted
Abstract [en]

Moisture dynamics in road systems significantly affect road structure design and maintenance. This study analysed moisture dynamics in a cross-section of motorway (the E18) in Sweden during a one-year period through in situ monitoring using electrical resistivity tomography (ERT). The monitoring methodology was assessed since resistivity can provide a good proxy for monitoring moisture in the road structure. Monthly electrical resistivity was calculated by inverting resistivity data along a pre-installed electrical resistivity line beneath the surface asphalt layer of the road at the test site. The electrical resistivity data were then statistically analysed and correlated with local climate data, i.e. precipitation and temperature, and with ground parameters such as moisture content. The results showed high variation in resistivity in the road surface layer and road shoulders depending on weather conditions, water flow and other surface activities. In general, negative correlations between electrical resistivity and precipitation were observed. The results also indicated possible retardation of de-icing salt after accumulating in the top layer during winter. These findings advance understanding of the moisture dynamics in roads and can help improve pavement design in response to future climate change.

Keywords
2D Electrical Resistivity Tomography; Road structures; Moisture content; in-situ monitoring; De-icing salt
National Category
Geophysical Engineering Water Engineering
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-226859 (URN)000448978300004 ()2-s2.0-85054475946 (Scopus ID)
Note

 Accepted for publication on 25 January 2018. QC 20180503

Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2018-11-22Bibliographically approved
Shamu, J., Zou, L., Kotzé, R., Wiklund, J. & Håkansson, U.Radial Flow Velocity Profiles of a Yield Stress Fluid between Smooth Parallel Disks.
Open this publication in new window or tab >>Radial Flow Velocity Profiles of a Yield Stress Fluid between Smooth Parallel Disks
Show others...
(English)Manuscript (preprint) (Other academic)
Keywords
2D-radial flow, plug-flow region, velocity profile, ultrasound velocimetry, slip, yield stress fluid (YSF), cement-based grouts
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering; Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-251625 (URN)
Funder
SBUF - Sveriges Byggindustriers Utvecklingsfond, 13470Rock Engineering Research Foundation (BeFo), 399
Note

QC 20190521

Available from: 2019-05-16 Created: 2019-05-16 Last updated: 2019-05-21Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0958-7181

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