Natural Dams and Internal Erosion: Field Study - Lake Hennan
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
In dam design, and especially for tailings dams, long term stability is of importance. One process that could endanger a dam construction is internal erosion, i.e. particle transportation by groundwater flow with in the dam that may result in a failure process. This is a known problem in dam construction but is poorly understood for long time perspective.In Sweden, glacial deposits have acted as natural dams for about 20,000 years. This implies that the composition of these deposits in combination with the present hydraulic gradient has been stable in a long term perspective. In this study such a formation, Lake Hennan, has been studied and compared with general dam design guidelines.The study has included a geotechnical field survey and subsequent laboratory investigations. The aim of the field survey was to explore the stratigraphy of the geological formation, collect samples for laboratory testing and collect ground water level observations. The laboratoryinvestigations targeted on classification of the collected samples mainly by sieving.The final conclusion from this study is that the geological formation at Lake Hennan is a natural dam. And it is an esker formation surrounded by lacustrine deposits of finer materials at the base adjacent to the upper and lower lakes. The groundwater observations indicate a maximum hydraulic gradient of 2.4%. Compared to the reviewed dam design guidelines based on gradation curves, the filter and suffusion criteria requirements are met. The permeability criteria based on gradation curves is not fulfilled since the amount of fines is too high.
Place, publisher, year, edition, pages
2011. , 111 p.
Technology, internal erosion, dam engineering, natural dam, filter, field study
IdentifiersURN: urn:nbn:se:ltu:diva-57602Local ID: e413b296-fbc8-45d1-a5b0-b976bac02f92OAI: oai:DiVA.org:ltu-57602DiVA: diva2:1030990
Subject / course
Student thesis, at least 30 credits
Civil Engineering, master's level
Validerat; 20110622 (anonymous)2016-10-042016-10-04Bibliographically approved