Testing dike stability under uplift conditions: an experimental study

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4. Testing dike stability under uplift conditions: an experimental study

Accurate safety assessment of water retaining structures requires a good understanding of all relevant failure mechanisms. One of the mechanisms that is not well understood includes uplift of low permeable layers at the toe of a dike or levee, which might result due to a hydraulic connection between the free water level and permeable subsoil layers. The uplift might induce either slope instability or start backward erosion piping. To improve the understanding of uplift of low permeable layers and its consequences for dike safety a series of centrifuge tests has been conducted. The test series varies with the thickness and pre-consolidation stress of the cover layer.

The tests confirm the hydraulic head development in the sand layer given by the guidelines, in which the hydraulic head is maximised by the weight of the uplifted layer. The uplift is manifested by a clear opening between sand and cover layer. When reaching uplift, all tests show crack development at the toe of the dike. The tests in which the clay was consolidated at low consolidation stress showed semi-horizontal crack development. In some cases, the semi horizontal cracks developed into a vertical chimney and corresponding sand boils. Slope failure was found after increasing g-level. The failure mechanisms contained a clear active failure. At the passive side no failure plane was found.

5th European Conference on Physical Modelling in Geotechnics (ECPMG2024)

Keynote paper