Workshop of the ISSMGE TC 32, 24-25 September 2010, Budapest [email protected]Dikes failures and limit states of the HYD in EC 7 Ivan Vaníček Czech Technical University in Prague Faculty of Civil Engineering Geotechnical Department 1 [email protected]
Dikes failures and limit states of the HYD in EC 7. Ivan Vaníček Czech Technical University in Prague Faculty of Civil Engineering Geotechnical Department. [email protected]. Earth structures in Water Engineering. Large dams Small dams Anti flood protection systems (Dikes) - PowerPoint PPT Presentation
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Workshop of the ISSMGE TC 32, 24-25 September 2010, Budapest
Workshop of the ISSMGE TC 302, 24-25 September 2010, Budapest
Hydraulic failure HYD
The provisions of the Section apply to four modes of ground failure induced by pore-water pressure or pore-water seepage, which shall be checked, as relevant:
• failure by uplift (buoyancy)• failure by heave• failure by internal erosion• failure by piping
Workshop of the ISSMGE TC 32, 24-25 September 2010, Budapest
Suitable structural measures are:
• application of berms on the land side of a retaining embankment, thus displacing the possible starting point of piping farther away from the structure and decreasing the hydraulic gradient at this point;
• application of impermeable screens below the base of the hydraulic structure by which the ground-water flow is either blocked or the seepage path is increased, thereby decreasing the hydraulic gradient to a safe value.
Workshop of the ISSMGE TC 302, 24-25 September 2010, Budapest
Internal erosion
Failure by internal erosion is produced by the transport of soil particles within a soil stratum, at the interface of soil strata, or at the interface between the soil and the structure. This may finally result in regressive erosion, leading to collapse of the soil structure.
Workshop of the ISSMGE TC 302, 24-25 September 2010, Budapest
Summary
Limit states which are playing most important role for earth structures in water engineering are:
Internal erosion (including piping)
Surface erosion
EC 7: Internal erosion is specified only in very broad way – also the way by which this limit state should be verified - can we use the adoption of prescriptive measures or experimental models?
Surface erosion is not specified at all (although was mentioned in early versions)
Workshop of the ISSMGE TC 302, 24-25 September 2010, Budapest
Surface erosion
In the Czech Republic we are using the experimental models and prescriptive measures:
Where it is possible to select the place where overflowing can start (causing minimum problems) - there the crest of dam (dike) is decreased (e.g. 0.3 m) and reinforced.