Vízügyi Közlemények, Kivonatok, 1965
Dégen Imre: Az 1965. évi dunai árvíz és árvízvédelmünk fejlődése
(4íf) b) The levees of non-uniform materials saturated from two directions , namely laterally from the riverside slope and vertically upward as a result of rising groundwater under the levee. Observations on the southern Danube reaches showed seepage lines to be typically concave when viewed from above. The saturated toes of levees were reinforced by sandbag and quarrystone ballasting. This proved to be effective, provided that departure of water from the levee body was permitted (Figs. 2 and 3). Supports taking the form of filter berms were also constructed by mechanical equipment (Fig. 4). This was also advantageous as it formed the core for subsequent final strengthening work. Where saturation and seepage through the levee increased under continued exposure to unbalanced head, a sheet pile cutoff was driven on the riverside (Fig. 5). Carefully driven, these proved effective. As a new method plastic foil was placed on the riverside slöpe. Where the cover v/as continuous and good sealing of the edges and overlaps could be realized, the levee became dry perceptibly (Fig. 6). Concentrated leakage occurred in rare instances only. Phenomena which could be traced back to underseepage under the levee body, caused the majority of difficulties. Upward seepage flow through the top cover caused pooling. Hydraulic pressures exceeding the submerged weight of the soil caused hydraulic soil failure, while boils emerged from passage in the top cover. Increased care and attention must be devoted in the future to the prevention of pooling and to the removal of waters already pooled landward of the levee. At exposed locations and where the impervious sublayer is at practicable depth impervious cutoff walls must be constructed in the courge of strengthening work after the flood. Counter-head was created against boils emerging through the top cover. The continuity of the latter must be preserved. Series of counterhead basins became necessary where numerous elementary boils appeared over large areas (Fig. 7). In many instances it was necessary to maintain several stages in the counter-head basins. Different types of sublevee were applied, namely of sandbags, earth and foil covered timber wall, to create counter-head basins. For reducing underseepage sheet-pile cutoffs were driven to depths of 8 and up to 10 m. In Chapter 2 the modernization of materials and equipment for active flood control is discussed. Altogether 4.2 million jute fabric sand bags were used in greatest quantities. Bags of plastic foil proved unsuccessful. The use of bags made of synthetic fibre must be introduced, which are pervious to air and water, have suitable strength and friction properties, can be stored for extended periods and do not decay even if submerged for a long time. The filling of sandbags must be mechanized.
