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Rönnqvist, Hans
Publications (10 of 15) Show all publications
Rönnqvist, H., Viklander, P. & Knutsson, S. (2017). Experimental Investigation of Suffusion in Dam Core Soils of Glacial Till (ed.). ASTM geotechnical testing journal, 40(3), 426-439
Open this publication in new window or tab >>Experimental Investigation of Suffusion in Dam Core Soils of Glacial Till
2017 (English)In: ASTM geotechnical testing journal, ISSN 0149-6115, E-ISSN 1945-7545, Vol. 40, no 3, p. 426-439Article in journal (Refereed) Published
Abstract [en]

The main objectives of this study were to determine the susceptibility to suffusion of widely graded, non-plastic glacial till; to identify potential factors influencing susceptibility; and conversely, to determine grading characteristics that potentially eliminate suffusion susceptibility. A laboratory experimental program was performed on 12 non-plastic glacial till specimens. Four were natural glacial tills sourced from the cores of four existing embankment dams in Sweden, and the remaining eight were mixtures based on these tills with adjusted particle size distributions to obtain target gradations. Four specimens failed by suffusion. By comparing against stable specimens, these were characterized by fines content <20 %, sand fraction <25 %, and finer fraction <30 %. Conversely, gradations with higher fines content (> 25 %), which in this study corresponds to finer fraction >35 %, may provide additional limits to suffusion susceptibility of this kind of soil.

Place, publisher, year, edition, pages
ASTM International, 2017
Keywords
embankment dams, internal erosion, internal stability, suffusion, filters, cores, glacial tills
National Category
Geotechnical Engineering
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-13071 (URN)10.1520/GTJ20150298 (DOI)000405477000003 ()2-s2.0-85051199710 (Scopus ID)c3afe618-d30e-433d-b94f-caa8707ae2dd (Local ID)c3afe618-d30e-433d-b94f-caa8707ae2dd (Archive number)c3afe618-d30e-433d-b94f-caa8707ae2dd (OAI)
Note

Validerad;2017;Nivå 2;2017-06-08 (rokbeg)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-08-17Bibliographically approved
Rönnqvist, H. & Viklander, P. (2016). A unified-plot approach for the assessment of internal erosion in embankment dams (ed.). Paper presented at . International Journal of Geotechnical Engineering, 10(1), 66-80
Open this publication in new window or tab >>A unified-plot approach for the assessment of internal erosion in embankment dams
2016 (English)In: International Journal of Geotechnical Engineering, ISSN 1938-6362, E-ISSN 1939-7879, Vol. 10, no 1, p. 66-80Article in journal (Refereed) Published
Abstract [en]

Surpassed only by overtopping as the larger contributor to the failure of embankment dams, internal erosion occurs when fine-grained particles are allowed to erode by the action of seepage. A dam may be susceptible to internal erosion if there are erodible surfaces not protected by filters. Signs of internal erosion of dams may be sinkhole formations, increased seepage and muddy discharge. Most methods to assess potential susceptibility are empirically based with little or no comparison to field experience. Based on a database of 80 embankment dams that includes 23 dams reported to have experienced some form of internal erosion and exhibited signs of internal erosion, analysis indicates a correlation between dams with internal erosion and characteristics of the filter of a dam. From comparison to field experience, an approach to assessing existing dams and internal erosion is proposed in this paper by combining attributes of filter gradation in a unified plot, namely its internal stability and its capacity for soil retention. The unified plot may serve as a preliminary screening tool for the susceptibility of internal erosion of dams.

Abstract [en]

Surpassed only by overtopping as the larger contributor to the failure of embankment dams, internal erosion occurs when fine-grained particles are allowed to erode by the action of seepage. A dam may be susceptible to internal erosion if there are erodible surfaces not protected by filters. Most methods to assess potential susceptibility are empirically based with little or no comparison to field experience. Based on a database of 80 embankment dams that includes 23 dams reported to have experienced some form of internal erosion, analysis shows a correlation between deficiencies attributed to internal erosion with the potential for internal instability and the capacity of the filter for soil retention. From comparison to field experience, an approach to assess existing dams and internal erosion is proposed by combining these two attributes of filter gradation in a unified plot. The finding implies that a unified plot may serve as a preliminary screening tool in engineering practice.

National Category
Geotechnical Engineering
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-6441 (URN)10.1179/1939787915Y.0000000002 (DOI)000371793100009 ()2-s2.0-84961806553 (Scopus ID)4aa8c9e2-3488-4402-98b3-b332bfec1fd2 (Local ID)4aa8c9e2-3488-4402-98b3-b332bfec1fd2 (Archive number)4aa8c9e2-3488-4402-98b3-b332bfec1fd2 (OAI)
Note
Validerad; 2016; Nivå 2; 20141121 (hayrof)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Rönnqvist, H. (2016). Response to downward seepage tests in glacial till with varying degrees of internal instability (ed.). In: (Ed.), : . Paper presented at International Conference on Scour and Erosion : 12/09/2016 - 15/09/2016.
Open this publication in new window or tab >>Response to downward seepage tests in glacial till with varying degrees of internal instability
2016 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

This paper explores how varying degrees of internal instability of glacial till soils affects grading characteristics due to internal erosion. Glacial till is used as impervious core material in many parts of the world. Internal erosion initiates by backward erosion, suffusion, contact erosion and concentrated leak erosion. The initiation mechanism of suffusion relates to the internal instability of a gradation, and backward erosion to an unfiltered interface. Based on a laboratory experimental program on 12 non-plastic glacial till specimens, four of which were natural glacial tills sourced from four existing embankment dams in Sweden and the remaining eight were mixtures with gravel based on these tills, insight is obtained as to the consequences of the stability index (H/F)min of a gradation when subjected to a downward gradient. Six specimens were stable, four failed by suffusion and two by backward erosion. Aspects such as erosion mass loss and seepage behaviour are discussed. Pre- and post-test gradations, effects on grading characteristics like the coefficient of uniformity, Cu, and the d10, as well as the coefficient of curvature, Cz, are detailed. This study will show that with increasing internal instability, there is an increase in mass loss due to internal erosion (suffusion) and increase in local gradient and variation in head loss distribution compared to the internally stable specimen. Furthermore, as expected, the stability index (H/F)min is subordinate to the filter incompatibility for the specimens that failed by backward erosion

National Category
Geotechnical Engineering
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-40304 (URN)f613421f-ae2d-42d5-9a04-57c417f3b1eb (Local ID)f613421f-ae2d-42d5-9a04-57c417f3b1eb (Archive number)f613421f-ae2d-42d5-9a04-57c417f3b1eb (OAI)
Conference
International Conference on Scour and Erosion : 12/09/2016 - 15/09/2016
Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-25Bibliographically approved
Rönnqvist, H. (2015). A tale of two dams: A comparative study of performance and internal erosion (ed.). Paper presented at International conference on geotechnical engineering : ICGE2015 Colombo 10/08/2015 - 11/08/2015. Paper presented at International conference on geotechnical engineering : ICGE2015 Colombo 10/08/2015 - 11/08/2015.
Open this publication in new window or tab >>A tale of two dams: A comparative study of performance and internal erosion
2015 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Internal erosion occurs when fine-grained particles are allowed to erode in a material by the action of seepage, and it is one of the major causes for the failure of embankment dams. Embankment dams are normally composed of zones, each with a purpose: the imperviousness of the core, the erosion-control and structure-stability provided by the filter and the support fill, respectively. A poorly functioning zone will adversely affect the performance of a dam, and the filter, if inadequate, is thus unable to protect against internal erosion of the core. Two existing embankment dams are studied herein, both are located in Sweden and with cores composed of glacial till against granular filter, but with different performance records; one has suffered a sinkhole-event due to internal erosion, the other has operated without signs of distress. A comparative assessment is performed by using available internal erosion criteria in the literature, and although relatively similar in design and composition the assessment reveals a possible explanation as to why there are differences in performance of these dams in terms of internal erosion.

National Category
Geotechnical Engineering
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-27807 (URN)15c48f12-b665-4e12-b7c1-bf1cceb63f4d (Local ID)15c48f12-b665-4e12-b7c1-bf1cceb63f4d (Archive number)15c48f12-b665-4e12-b7c1-bf1cceb63f4d (OAI)
Conference
International conference on geotechnical engineering : ICGE2015 Colombo 10/08/2015 - 11/08/2015
Note
Godkänd; 2015; 20150407 (hayrof)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Rönnqvist, H. & Viklander, P. (2015). Applying empirical methods to assess the internal stability of embankment dam cores of glacial till (ed.). Geomaterials, 5, 1-18
Open this publication in new window or tab >>Applying empirical methods to assess the internal stability of embankment dam cores of glacial till
2015 (English)In: Geomaterials, ISSN 2161-7538, E-ISSN 2161-7546, Vol. 5, p. 1-18Article in journal (Refereed) Published
Abstract [en]

This paper presents a database of glacial till gradations that were compiled from laboratory in-ternal stability tests from the literature and from core soils of existing dams, some of which have experienced internal erosion. The potential internal instability of these gradations is assessed using empirical methods. Two approaches of evaluation are used: the Kenney-Lau method, which analyzes the shape of the gradation curve; and the Burenkova method, which uses factors of uniformity of the slope of the gradation. Although they include some uncertainties in terms of soils with fines, these methods, which were primarily developed from laboratory studies of sand and gravels, are used in engineering practice to evaluate widely graded soils that include fines, such as glacial tills. This study evaluates the glacial till gradations of the database using these approaches and discusses their applicability and relative predictive success. This study indicates that both the Kenney-Lau method and the Burenkova method have merit, but a closer analysis indicates that the Kenney-Lau approach has better predictive ability in terms of glacial tills.

National Category
Geotechnical Engineering
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-3681 (URN)10.4236/gm.2015.51001 (DOI)18024e50-578c-4f98-80c5-07386d392c86 (Local ID)18024e50-578c-4f98-80c5-07386d392c86 (Archive number)18024e50-578c-4f98-80c5-07386d392c86 (OAI)
Note

Godkänd; 2014; 20141028 (hayrof)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-06-26Bibliographically approved
Rönnqvist, H., Fannin, J., Viklander, P. & Wang, L. (2015). Discussion: On the use of empirical methods for assessment of filters in embankment dams (ed.). Paper presented at . Geotechnique Letters, 5(July-September), 140-141
Open this publication in new window or tab >>Discussion: On the use of empirical methods for assessment of filters in embankment dams
2015 (English)In: Geotechnique Letters, E-ISSN 2045-2543, Vol. 5, no July-September, p. 140-141Article in journal, Editorial material (Refereed) Published
Abstract [en]

We first give consideration to the question that Wang, Yang and Ye pose on the distribution of data points in Fig. 4a and 4b of the paper under discussion, because it addresses an informative point that we believe may indeed benefit from a note of clarification. An assessment of the potential for seepage-induced internal instability in, for example, the filter material of a dam usually involves an evaluation of gradation curves obtained from construction records and any subsequent investigations. If more than one empirical method is used for shape analysis of the gradations, then several most-vulnerable curves may be identified from the analyses, owing to the empirical origins of the methods themselves.

National Category
Geotechnical Engineering
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-8900 (URN)10.1680/geolett.14.00114 (DOI)000359265700009 ()772b8863-9a79-4ceb-b7d7-2cccc9e2a3f5 (Local ID)772b8863-9a79-4ceb-b7d7-2cccc9e2a3f5 (Archive number)772b8863-9a79-4ceb-b7d7-2cccc9e2a3f5 (OAI)
Note
Godkänd; 2015; 20150313 (hayrof)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Rönnqvist, H. (2015). Om två dammar: En jämförande studie och utvärdering av inre ersosion (ed.). Paper presented at Grundläggningsdagen 2015 : 12/03/2015 - 12/03/2015. Paper presented at Grundläggningsdagen 2015 : 12/03/2015 - 12/03/2015.
Open this publication in new window or tab >>Om två dammar: En jämförande studie och utvärdering av inre ersosion
2015 (Swedish)Conference paper, Oral presentation only (Other academic)
Abstract [sv]

Inre erosion uppstår om finkorniga partiklar tillåts förflyttas av läckageflöde i ett material och det är en av de största orsakerna till dammbrott hos fyllningsdammar. Fyllningsdammar utgörs normalt av flera zoner, vardera med ett syfte: tätkärnan för vattentäthet, filtret som skyddar mot inre erosion och stödfyllningen som ger stabilitet mot laster. En bristande funktion hos någon zon påverkar dammens funktion negativt och ett bristande filter gör alltså att tätkärnan ej är skyddad mot inre erosion. Två fyllningsdammar studeras, bägge i Sverige och med tätkärna av morän, men med olika drifterfarenheter; den ena med sjunkhål på grund av inre erosion och den andra utan anmärkningar. Med hjälp av en utvärderingsmetod (”unified-plot”) görs en jämförande studie av känslighet för inre erosion. Trots att utformning och sammansättning är relativt likartade visas häri en möjlig förklaring till varför dammarna ändå har betett sig olika driftmässigt vad gäller inre erosion.

National Category
Geotechnical Engineering
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-28274 (URN)2046f6dd-972b-4378-8cf7-4e1266cc2b25 (Local ID)2046f6dd-972b-4378-8cf7-4e1266cc2b25 (Archive number)2046f6dd-972b-4378-8cf7-4e1266cc2b25 (OAI)
Conference
Grundläggningsdagen 2015 : 12/03/2015 - 12/03/2015
Note
Godkänd; 2015; 20150313 (hayrof)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Rönnqvist, H. (2015). On the Assessment of Internal Erosion of Dam Cores of Glacial Till (ed.). (Doctoral dissertation). Paper presented at . : Luleå tekniska universitet
Open this publication in new window or tab >>On the Assessment of Internal Erosion of Dam Cores of Glacial Till
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Utvärdering av benägenhet för inre erosion i dammtätkärnor av morän
Abstract [en]

The objective of this study is twofold; on the one hand it investigates the susceptibility to suffusion of glacial till, and, on the other, it presents approaches to evaluate internal erosion susceptibility of dams composed of this type of core soil. Concentrated leak erosion, backward erosion, contact erosion, and suffusion erosion are the mechanisms associated with the initiation of internal erosion. How these interplay in the continuation phase is still a relatively unresolved issue. In engineering practice, these mechanisms have all been seen in dams with glacial till cores; backward erosion activity as seen in Juktan dam, Juklavatn dam, Grundsjöndam, Wreck Cove dam, and in Brodhead dam; possible suffusion as seen in Lövön dam and in Stenkullafors dam; and, furthermore, signs indicating concentrated leaks, such as in Songa dam. A laboratory program of tests was performed on four natural, non-plastic glacial till soils from the core or its borrow area of existing earth dams in Sweden, and on eight mixtures based on these tills, making in total 12 tests. The longest running for 77 days, and the highest applied gradient was 9.5, in bounds of what can occur in dam cores. The tests revealed that gradations of low fines content (< §15–20%), low sand fraction (< §20%), and high gravel fraction (> §60%) are susceptible to suffusion. These are grading characteristics present in the coarse end of the envelope of glacial till cores in many existing dams. Available state-of-the-art assessment criteria for internal stability were evaluated in reference to these experimental data, yielding a modification to the Kenney-Lau adaptation by Li-Fannin. Furthermore, a screening tool for the assessment of internal erosion of dams is proposed, i.e., the unified-plot approach, which combines attributes of the filter gradation and the probable occurrence of internal erosion in a dam. Given the variety of potential mechanism interplaying in the internal erosion of dams with cores of glacial till, it lend confidence to an assessment approach which addresses, susceptibility to several mechanisms.

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2015
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Geotechnical Engineering
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-25943 (URN)bd28736b-fa6a-4707-8bae-ecfaafc254f4 (Local ID)978-91-7583-336-1 (ISBN)978-91-7583-337-8 (ISBN)bd28736b-fa6a-4707-8bae-ecfaafc254f4 (Archive number)bd28736b-fa6a-4707-8bae-ecfaafc254f4 (OAI)
Note
Godkänd; 2015; 20150417 (hayrof); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Hans Rönnqvist Ämne: Geoteknik/Soil Mechanics and Foundation Engineering Avhandling: On the Assessment of Internal Erosion of Dam Cores of Glacial Till Opponent: Professor emeritus Kaare Höeg, Universitetet i Oslo/Norges Geotekniska Institut (NGI), Oslo, Norge Ordförande: Professor Sven Knutsson, Avd för geoteknologi, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet, Luleå Tid: Onsdag 10 juni 2015, kl 10.00 Plats: F1031, Luleå tekniska universitetAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-24Bibliographically approved
Rönnqvist, H. (2015). Predicting suffusion potential of dam core soil of glacial till (ed.). In: (Ed.), (Ed.), Eksploatacja budowli piętrzących: diagnostyka i zapobieganie zagrożeniom. Paper presented at Dam Monitoring International Conference : 29/09/2015 - 02/10/2015. Warszawa: Instytut Meteorologii i Gospodarki Wodnej − Państwowy Instytut Badawczy
Open this publication in new window or tab >>Predicting suffusion potential of dam core soil of glacial till
2015 (English)In: Eksploatacja budowli piętrzących: diagnostyka i zapobieganie zagrożeniom, Warszawa: Instytut Meteorologii i Gospodarki Wodnej − Państwowy Instytut Badawczy , 2015Conference paper, Published paper (Refereed)
Abstract [en]

Although extensively used as core material in dams in many parts of the world, internal instability and suffusion potential of glacial till is still a relatively unexplored field. Statistically, dams with cores of glacial till have higher frequency of internal erosion incidents than dams with other types of core soils. Such potential overrepresentation may stem back to the erodibility of the glacial till itself. One mechanism that may be influential is suffusion due to internal instability. The literature offers several methods to evaluate a soils vulnerability to this mechanism, however, in terms of glacial till soils; the validity of assessment criteria is unclear. An offset in applicability may, at best, provide too conservative guidance, but at worst, it may be misleading, confusing or erroneous. Thus, the applicability of available state-of-the-art criteria for internal instability of glacial till soils is investigated in this paper. Using gradations from: laboratory tests performed by the author at Luleå University of Technology; gradations from experimental suffusion tests in the literature; and gradations from existing dams, a total of 36 glacial till gradations are evaluated. The study indicates that the approach by Kenney-Lau and its Li-Fannin adaptation provide predictions relatively more accurate in identifying glacial till gradations with unstable performance due to suffusion.

Place, publisher, year, edition, pages
Warszawa: Instytut Meteorologii i Gospodarki Wodnej − Państwowy Instytut Badawczy, 2015
National Category
Geotechnical Engineering
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-33115 (URN)7e62ea36-6664-4547-8940-3023f72c5f72 (Local ID)978-83-64979-09-5 (ISBN)7e62ea36-6664-4547-8940-3023f72c5f72 (Archive number)7e62ea36-6664-4547-8940-3023f72c5f72 (OAI)
Conference
Dam Monitoring International Conference : 29/09/2015 - 02/10/2015
Note
Godkänd; 2015; 20150515 (hayrof)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Rönnqvist, H., Fannin, J. & Viklander, P. (2015). The unified plot approach for assessing internal erosion: A case study of the Grundsjön dam sinkhole event (ed.). Paper presented at ICOLD Congress 2015 : International Commission on Large Dams 15/06/2015 - 16/07/2015. Paper presented at ICOLD Congress 2015 : International Commission on Large Dams 15/06/2015 - 16/07/2015.
Open this publication in new window or tab >>The unified plot approach for assessing internal erosion: A case study of the Grundsjön dam sinkhole event
2015 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

The unified plot approach combines two attributes of a filter gradation, namely its potential for internal instability and its capacity for soil retention. Comparison to the performance of 80 existing embankment dams that includes 23 dams which are reported to have experienced some form of internal erosion, these attributes of the filter have been found to correlate with deficiencies related to internal erosion. Thus, in engineering practice, the unified plot may serve as a screening tool for internal erosion susceptibility. The Grundsjön dam, located on the river Ljusnan in Sweden, suffered a sinkhole event in 1990, 18 years after commissioning. In depth examination of the damaged stretch of the dam conducted in 1990 to 1991 revealed that internal erosion had indeed occurred; signs e.g., cavities in the core and filter devoid of fines suggest the process had initiated and been allowed to continue to the point that a sinkhole formed on the crest. Analysis of 43 as-placed filter gradations extracted from the Grundsjön dam filter envelope indicates that the filter is potentially unstable, although, not excessively coarse in terms of base soil retention. These results, as seen separately, provide relatively little explanation as to why the filter ultimately was unable to arrest the internal erosion process. However, combined, in the framework of the unified plot, it is readily apparent that the Grundsjön dam filter gradations distribute where dams with probable occurrence of internal erosion characteristically plot. Thus, the unified plot provides a plausible explanation for the internal erosion process that occurred. Indeed, reverse engineering the potential internal instability of the coarse filter gradation indicates that once changed by suffusion due to internal instability it potentially becomes a filter permitting excessive erosion.

National Category
Geotechnical Engineering
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-31245 (URN)55cc5820-93fa-4c1e-bb3b-2098de524038 (Local ID)55cc5820-93fa-4c1e-bb3b-2098de524038 (Archive number)55cc5820-93fa-4c1e-bb3b-2098de524038 (OAI)
Conference
ICOLD Congress 2015 : International Commission on Large Dams 15/06/2015 - 16/07/2015
Note
Godkänd; 2015; 20141028 (hayrof)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-06-26Bibliographically approved
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