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The unified plot approach for assessing internal erosion: A case study of the Grundsjön dam sinkhole event
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
University of British Columbia.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
2015 (English)Conference paper, Presentation (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.

Place, publisher, year, edition, pages
Research subject
Soil Mechanics
URN: urn:nbn:se:ltu:diva-31245Local ID: 55cc5820-93fa-4c1e-bb3b-2098de524038OAI: diva2:1004475
ICOLD Congress 2015 : International Commission on Large Dams 15/06/2015 - 16/07/2015
Godkänd; 2015; 20141028 (hayrof)Available from: 2016-09-30 Created: 2016-09-30Bibliographically approved

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Rönnqvist, HansViklander, Peter
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