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Hydraulic Conductivity of Coarse Rockfill used in Hydraulic Structures
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
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.

Place, publisher, year, edition, pages
2015. Vol. 108, no 2, 367-391 p.
Keyword [en]
Embankment dam failure due to internal erosion, Hydraulic conductivity, Coarse rockfill, Nonlinear flow law
National Category
Other Engineering and Technologies
Identifiers
URN: urn:nbn:se:kth:diva-169131DOI: 10.1007/s11242-015-0481-1ISI: 000354207300007OAI: oai:DiVA.org:kth-169131DiVA: diva2:820407
Note

QC 20150612

Available from: 2015-06-12 Created: 2015-06-11 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Internal Erosion Phenomena in Embankment Dams: Throughflow and internal erosion mechanisms
Open this publication in new window or tab >>Internal Erosion Phenomena in Embankment Dams: Throughflow and internal erosion mechanisms
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
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:nbn:se:kth:diva-193627 (URN)978-91-7729-130-5 (ISBN)
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

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