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Internal Erosion Phenomena in Embankment Dams: Throughflow and internal erosion mechanisms
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering. (Hydraulic Engineering)
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

 In this study, two major internal erosion initiation processes, suffusion and concentrated leak mechanisms, which lead to both defect formation in a dam’s body and its foundation and high throughflow in dams subjected to internal erosion were studied. This understanding has the potential to facilitate numerical modelling and expedite dam safety assessment studies. 

The throughflow properties of coarse rockfill material were studied by; analysing filed pump test data, performing extensive laboratory experiments with a large-scale apparatus and numerically simulating the three-dimensional flow through coarse rock materials, replicating the material used in the laboratory experiments.

Results from the tests demonstrate that the parameters of the nonlinear momentum equation of the flow depend on the Reynolds number for pore Reynolds numbers lower than 60000. 

Numerical studies were also carried out to conduct numerical experiments. By applying a Lagrangian particle tracking method, a model for estimating the lengths of the flow channels in the porous media was developed.  The shear forces exerted on the coarse particles in the porous media were found to be significantly dependent on the inertial forces of the flow.

Suffusion and concentrated leak mechanisms were also studied by means of laboratory experiments to develop a theoretical framework for continuum-based numerical modelling. An erosion apparatus was designed and constructed with the capability of applying hydraulic and mechanical loading. Results were then used to develop constitutive laws of the soil erosion as a function of the applied hydromechanical load for both suffusion and concentrated leak mechanisms. Both the initiation and mass removal rate of were found to be dependent on the soil in-situ stresses.

A three-dimensional electrical-resistivity-based tomography method was also adopted for the internal erosion apparatus and was found to be successful in visualising the porosity evolution due to suffusion.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , 74 p.
Series
TRITA-HYD, 2016:4
Series
ISSN, ISSN 1650-8602
Keyword [en]
Internal erosion modelling in porous material; Constitutive law of erosion for closure of continuum-mechanics-based balance equations for numerical modelling; High Reynolds-number turbulent flow; Flow laws; Coarse rockfill material throughflow; Computational Fluid Dynamics.
National Category
Geotechnical Engineering Water Engineering
Research subject
Civil and Architectural Engineering
Identifiers
URN: urn:nbn:se:kth:diva-193627ISBN: 978-91-7729-130-5 (print)OAI: oai:DiVA.org:kth-193627DiVA: diva2:1033267
Public defence
2016-11-04, Kollegiesalen, Brinellvägen 8, Stockholm, 09:00 (English)
Opponent
Supervisors
Note

QC 20161006

Available from: 2016-10-06 Created: 2016-10-06 Last updated: 2016-10-11Bibliographically approved
List of papers
1. Characterization of hydraulic behaviours of coarse rock materials in a large permeameter
Open this publication in new window or tab >>Characterization of hydraulic behaviours of coarse rock materials in a large permeameter
2013 (English)In: Journal of Geoscience and Environment Protection, ISSN 2327-4336, Vol. 1, no 3, 1-6 p.Article in journal (Refereed) Published
Abstract [en]

The hydraulic behavior of a rock material structure is a major feature for its design and safety assessment. Similar to all other physical prob-lems, in order to enclose the governing equations systems and achieve a solution, the hydraulic characteristics of these materials need to be determined experimentally and implemented then into adopted thermo-dynamical models. This paper covers the process of the design, con-struction and operation of an experimental rig built for this specific purpose. Using the constructed large-scale permeameter, tests have been conducted. The non-linear hydraulic behavior of various materials under extreme turbulent conditions, where Reynolds number reaches un-precedented values, has not been studied before. Preliminary results are presented and discussed.

Place, publisher, year, edition, pages
Scientific Research Publishing, 2013
Keyword
Experimental study; Permeameter; Coarse rock material; Turbulent flow; Reynolds number
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-179743 (URN)10.4236/gep.2013.13001 (DOI)
Note

QC 20160107

Available from: 2015-12-22 Created: 2015-12-22 Last updated: 2017-01-12Bibliographically approved
2. Hydraulic Conductivity of Coarse Rockfill used in Hydraulic Structures
Open this publication in new window or tab >>Hydraulic Conductivity of Coarse Rockfill used in Hydraulic Structures
2015 (English)In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 108, no 2, 367-391 p.Article in journal (Refereed) Published
Abstract [en]

Internal erosion is a major cause of embankment dam failure. Unravelling and instability of the downstream slope, initiated by internal erosion and leakage through the dam core, is one of the most likely breach mechanisms for large, zoned embankment dams. To be able to model this mechanism, the relationship between the hydraulic gradient and the flow velocity for the coarse rockfill material must be understood. Because most studies of this topic have focused on the flow parameters in gravel-size materials with Reynolds (Re) numbers lower than 25,000, permeability measurements are needed coarser rockfill material under heavily turbulent flow regimes prevailing in rockfill material under certain design flow scenarios. This paper presents the set-up and results of a series of field and laboratory experimental studies and the subsequent data interpretation, from which relevant hydraulic conductivity parameters, defined in applicable flow laws, were extracted. This study demonstrates that the exponent of a power flow law relating the hydraulic gradient and the flow velocity is Re number dependent for pore Re numbers 60,000. The power remains constant (Re number independent) above this Re number threshold for the fully developed turbulent regime. This validity threshold as well as the constant behaviour also applies if the flow law is written in a quadratic form. The aforementioned threshold lies beyond the ranges investigated experimentally by previous researchers. The experiments in this study examined Re numbers as large as 220,000 for grain-diameter distributions in the range 100-160 mm and as large as 320,000 in the range 160-240 mm.

Keyword
Embankment dam failure due to internal erosion, Hydraulic conductivity, Coarse rockfill, Nonlinear flow law
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-169131 (URN)10.1007/s11242-015-0481-1 (DOI)000354207300007 ()
Note

QC 20150612

Available from: 2015-06-12 Created: 2015-06-11 Last updated: 2017-12-04Bibliographically approved
3. A study of turbulent flow in large-scale porous media at high Reynolds numbers. Part I: numerical validation
Open this publication in new window or tab >>A study of turbulent flow in large-scale porous media at high Reynolds numbers. Part I: numerical validation
2016 (English)In: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 54, no 6, 663-677 p.Article in journal (Refereed) Published
Abstract [en]

Analyses of turbulent flows through the downstream slopes of embankment dams are important for dam safety assessments, especially considering high-risk scenarios such as a sudden release of water due to internal erosion. Flow prediction is difficult in such situations due to coarseness of construction materials and high Reynolds numbers. The present study addresses this issue through comprehensive numerical modelling. The novelty of the proposed approach lies in a combination of large-scale experiments and three-dimensional numerical simulations, leading to a fully calibrated and validated model that is applicable to flows through cobble-sized materials (100–160 mm in diameter) at high Reynolds numbers (>104). Comparing the results of the standard turbulence models to data from the large-sale experiments, the renormalization group theory-based model yielded the smallest relative errors based on the hydraulic gradients. Considering the flow field, the turbulent shear stress increased by a factor of 17, and the time-averaged vorticities intensified by factors of 2, 6 and 10 for vorticities in the x-, y- and z-directions, respectively, due to the presence of cobbles.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2016
Keyword
CFD validation, high Reynolds number turbulence, laboratory studies, numerical turbulence models, porous media flow
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-193718 (URN)10.1080/00221686.2016.1211184 (DOI)000386438300005 ()2-s2.0-84982292500 (Scopus ID)
Note

QC 20161121

Available from: 2016-10-10 Created: 2016-10-10 Last updated: 2017-11-29Bibliographically approved
4. A study of turbulent flow in large-scale porous media at high Reynolds numbers. Part II: flow physics
Open this publication in new window or tab >>A study of turbulent flow in large-scale porous media at high Reynolds numbers. Part II: flow physics
2016 (English)In: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 54, no 6, 678-691 p.Article in journal (Refereed) Published
Abstract [en]

The evaluation of hydraulic performance of coarse porous media at high Reynolds numbers is of significant importance for dam safety assessment. To address this task, the present study uses a numerical approach based on a rigorous theoretical framework. The novelty of the study lies in the application of a fully calibrated and validated numerical three-dimensional model and a set of modified equations for momentum transfer and the associated coefficients for flow in porous media. A Lagrangian particle tracking model was used to estimate the lengths of the flow channels that developed in the porous media. Gamma distributions were fitted to the normalized channel lengths, and the scale and shape parameters of the gamma distribution were found to be Reynolds number dependent. These shape parameters can be estimated from the suggested polynomial equations. The proposed normalized length parameter can be used to evaluate permeability, energy dissipation, induced forces, and diffusion. It was found that shear forces exerted on the coarse particles depend on the inertial forces of the flow and can be estimated using the proposed equation for the developed turbulent flows in porous media.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2016
Keyword
Numerical experimentation, particle tracking, porous-media flow, shear turbulence, wall-bounded flows
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-193719 (URN)10.1080/00221686.2016.1211185 (DOI)000386438300006 ()2-s2.0-84984669595 (Scopus ID)
Note

QC 20161011

Available from: 2016-10-10 Created: 2016-10-10 Last updated: 2017-11-29Bibliographically approved
5. Mechanism of suffusion erosion phenomenon in embankment dams
Open this publication in new window or tab >>Mechanism of suffusion erosion phenomenon in embankment dams
2016 (English)Manuscript (preprint) (Other academic)
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-193720 (URN)
Note

QC 20161011

Available from: 2016-10-10 Created: 2016-10-10 Last updated: 2016-10-12Bibliographically approved
6. Mechanism of concentrated leak erosion phenomenon in embankment dams
Open this publication in new window or tab >>Mechanism of concentrated leak erosion phenomenon in embankment dams
2016 (English)Manuscript (preprint) (Other academic)
National Category
Geotechnical Engineering Water Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-193721 (URN)
Note

QC 20161011

Available from: 2016-10-10 Created: 2016-10-10 Last updated: 2016-10-12Bibliographically approved
7. Detecting internal erosion processes in porous media by an Arduino-based electrical impedance tomography system developed on laboratory scale
Open this publication in new window or tab >>Detecting internal erosion processes in porous media by an Arduino-based electrical impedance tomography system developed on laboratory scale
(English)Manuscript (preprint) (Other academic)
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-193722 (URN)
Note

QC 20161011

Available from: 2016-10-10 Created: 2016-10-10 Last updated: 2016-10-11Bibliographically approved

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