Vízügyi Közlemények, Kivonatok, 1965

1. Az 1965. évi dunai árvíz - 1.1. Body K.-Csoma J.-Károlyi Z.-Szilágyi J.: Az 1965. évi dunai árvíz hidrológiai okai és lefolyása

(52) The methods of strengthening under b) and c) are only appropriate, and thus stability of the levee is only ensured where the stability of the soil block under the levee is also ensured at the particular foundation width (e.g., where the top cover is sufficiently thick). Over considerable lengths of levee along the Danube different degrees of stability exist, however, for the levee and the underlying soil block. Consequently, in the case of the Danube levees, from among the two possible methods of strengthening, namely flattening the landward slope and ballasting with a free draining material the landward slope, the one which provides a longer seepage path under the levee, i.e., a greater foundation width besides ensuring the stability of the landward slope, should be preferred. For improving the safety of both slope and foundation, strengthening should therefore be realized by added earthwork. The flatter slope should not be restricted to the section below the emergence of the line of seepage, but should be used for half, or even full height of the levee. Both the preferable slope of the levee and the required width of the filter ballast are to be determined by simple approximating calculations. Sonsidering embankment materials along the Danube, slopes inclined at from 1 : 4 to 1 : 8 appear suitable. 2. Embankment material placed on the landward side to flatten the slope must always have a greater, or at least equal permeability, than the material of the existing levee to the riverside of it. This condition involves special requirements fro the excavation and placement of material. With the exception of rare favourable circumstances these criteria can be satisfied best and most economically by the hydraulic fill method of construction. As is well known also in the case of flood levees cross sections composed of several materials ensure most readily the required stability. Owing to the predominantly linear character and considerable volume of construction the number of portions consisting of materials of different permeability can in general be reduced to two. One of these has the task of providing imperviousness, the other that of ensuring stability. The first must be placed on the riverside, while the second on the landward side of the levee. Construction becomes thus more complex than in the case of cross sections of uniform material and necessitates the use of up-to-date machinery and equipment. The hydraulic-fill method of construction is also from this respect very advantageous for levee construction along the Danube. 3. Counter measures against undesirable effects of underseepage and strengthening of the levees for this contingency must be based on extensive investigations in the case of Danube levees. These investigations must be extended to the study of environment of the levees, the exploration of foundation soil and the determination of permeability and even depth of the foundation layer. Besides the character of the foundation