Dike failure

What is it about?

World experiences reveal that catastrophic floods are posing a serious threat that comes not only from them as extreme events but also as the result of adaptation measures uncertainty, (i.e. dikes). In particularly old dikes constructed earliest at the north part of Albania, during the last floods demonstrated the high uncertainty and weak spots. In this paper, the significance of the seepage investigation and stability analysis are discussed. As a case study, parts of new dikes constructed last years along the Buna River located in north part of Albania are investigated. Filling materials for these dikes are represented mostly from silt and clay. Finite element method is used to perform seepage analysis while general limit equilibrium method is used to perform slope stability analysis. Both, seepage and slope stability analyses are done for three different scenarios: steady state, rapid filling, and rapid drawdown. Finally, it is concluded that silt-clay material used in these dike structure is posing serious uncertainty during seepage phenomenon by threatening the stability of entire dike structure especially during the transient condition (rapid filling and drawdown).

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Photo by Cédric Dhaenens on Unsplash

Photo by Cédric Dhaenens on Unsplash

Why is it important?

In this paper seepage process and slope stability of dike, structure is investigated through numerical modeling for different scenarios. Scenarios considered during numerical modeling are as following: steady state, rapid filling and rapid drawdown. The investigation of seepage process during the first scenario revealed that there is certain water volume passing through the dike structure. In this case, there is no any threat concerning the stability of dike, even that presence of water inside the dike structure lead to a reduction of mechanical properties of soil. For second scenario, safety factor is increased significantly up to 5.71 but the reduction of shear strength indicates that increase of dike stability is just temporary phenomenon’s that happen as result of temporary compaction of the filling materials by hydrostatic forces. Whereas during the third scenario; stability of the dike structure is decreased compared with the two first scenarios, safety factor achieved during this scenario is 2.43. The decreasing of the factor of safety is revealed perceptibly by the significant reduction of soils parameters like; shear strength as presented on the respective graph. In this case study is noticed that during rapid filling Finally after detailed investigation of the seepage phenomenon through the dike structure, it is conclude that internal and external hydrodynamic processes and especially seepage is a serious threat that should be considered not just during design process but also operation, even that materials used for construction of the dike structure or earth structures in generally may have very good parameters. In addition, designers should be aware what kind of filling materials should be used for construction of earth structures and adaptation measures in case of structure failure. Especially for high earth structures, using silt-clay as filling materials, based on standards recommended may lead to the rapture of structure and then catastrophic disaster. Also, proper riprap layers should be considering during the design phase in order to increase the safety of dike structure and to prevent any possible failure.

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