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Stability and Failure Mechanisms of Dams. A dam safety research project. Kjetil Arne Vaskinn. Simulation of flood propagation resulting from dam-break Breach development: Size of the breach as a function of time. Teton. Teton. Background.
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Stability and Failure Mechanisms of Dams A dam safety research project Kjetil Arne Vaskinn
Simulation of flood propagation resulting from dam-break Breach development: Size of the breach as a function of time Teton Teton Background • During the latest year there have been a strong focus on dam safety. This has been reflected by: • several reassessments of dam safety • new dam safety regulations • introduction of risk analysis • dam-break flood routing • etc. • Reassessment: • Uncertainty and discussion about the dam regarding the demand of: • Stability • Slide or erosion during large throughflow • Drainage capacity • The cost of rehabilitation is several millions of NOK at each dam
Aim of the project • Increase the knowledge about: • Safety of the downstream shell in Norwegian dams during large throughflow. • Breach formation in embankment and concrete dams. • The results shall be user-friendly, so that it can easily be used in the damowners safety work: • Design tool • Design criteria • Simplified point of view • Results are hoped to become a base for new “accept criteria".
Subproject no. 1: Shear strength and permability of rock-fillings • Find shear strength and stability of different embankment material • Find correct material parameters • Find realistic analyse methods • Literature study • Discussions with international experts • Summarize experiences from dams • Evaluation of earlier tests and calculations • Field tests Project manager: Kaare Høeg, NGI
Subproject no. 2: Stability and failure mechanisms of dams Damtoe Water tight core Support filling Filter Piping Overtopping Develop tools/routines for evaluating the stability based on tests and international experiences from similar topics. • Parameters that are studied: • Particle size • Grading of the material • Downstream slope • Tailwater level • Scale effects • Subproject status: • Field tests, carried out/new are planned • Laboratory tests, carried out/new are planned • Data reports, nearly finished • Analysis, ongoing Project manager: Einar Ødemark, Statkraft Grøner AS
Subproject no. 3: Breach formation in embankments • Study the failure mechanisms of rockfill dams using tests and data from earlier failures. • Develop methods for breach analysis. Design and layers of the dam should be included. • Subproject status: • Literature study • Field tests • Field- and laboratory tests from subproject no. 2 and IMPACT Project manager: Einar Ødemark, Statkraft Grøner AS
Subproject no. 4: Breach formation in concrete dams Study the failure mechanisms of different kind of concrete dams using Finite Element Method. • Subproject status: • Initial phase • Literature study planned and started? Project manager: Per Magnus Johansen, Norconsult
0.7 0.9 0.4 1.8 meter 0.5 m 1:1 Qut Qinn 1.2 m Water-level measurement 1:1.5 1:1.5 1:3 0.5 m Laboratory model – 0.6 m high dam
Laboratory model - scale 1:10 Downstream slope: 1:1.5 Tailwater level: Low Uniformly graded material d10 = 78 mm d50 = 100 mm Largest particle size tested in this flume Downstream slope: 1:1.5 Tailwater level: Low Uniformly graded material d10 = 5 mm d50 = 11 mm Smallest particle size tested in this flume
1.20 1.20 s Qut 1.8 3.6 1.0 3.6 meter 1.60 1:1 Filter Qmax = 600 l/s 4.00 1:3 Water-level measurement 1:1 Laboratory model – 1.2 m high dam
Test-flume scale 1:5 Downstream slope: 1:1.5 Tailwater level: Low Uniformly graded material d10 = 66 mm d50 = 88 mm
Project scheme, 2002 Finalise data reports from the tests in 2001 Analysis based on tests and literature Field tests Laboratory tests Literature studies Workshop