Erodibility of a dike in case of overflowing

• Autor(a) principal: Castro, Francisco Leite de
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/13984
• topic: Engenharia civil; Diques; Construções em terra

Earthen dikes (or earthen levees) are built all over the world, both in coastal (coastal dikes) and inland areas (riverine dikes), to protect population, infrastructures and resources from high water levels due to storm surges and seasonal floods. Most of these flood defence embankments are not prepared to resist to surface soil erosion of its crest and landside slope induced by overflowing events, and hence, maybe at risk of failure. Mitigation of dike damage by overflow may be accomplished by providing erosion protection on the surface of the crest and dike landside slope. Erosion protection can be conferred by a variety of materials (rip-rap, concrete, geosynthetics, etc.) ranging from hard armouring to light armouring alternatives. The present dissertation focuses on strengthening systems consisting of lightweight, flexible, synthetic mats such as (high performance) turf reinforcement mats and geogrids. The goal of this dissertation was to assess their effectiveness as a slope erosion protection system and to obtain some performance criteria under overflow conditions created through full-scale laboratory testing on a hydraulic model. Waterflow discharge, flow thickness and mean (horizontal) velocity measurements were acquired at one location on the landside slope channel (1V:4H) (near the downward edge of the slope). These measurements allowed to estimate shear stress ranges at the bed channel and Manning’s roughness coefficients. Some tentative empirical equations were presented correlating shear stress and flow thickness estimations with overflowing discharges. The results are strictly limited to the tested coarse-grained soil and rolled erosion control products as well as the range of tested hydraulic parameters possible to be attained on the hydraulic model. The experimental study mainly allowed to obtain some qualitative conclusions, in which it was proven that a reinforced surface soil layer with synthetic mats of a dike slope can withstand higher overflowing discharges than bare soil, without catastrophic sediment motion.