Vízügyi Közlemények, 1969 (51. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(47) Calculations have revealed for a 400 m range around a group of inrush points with a total discharge of 27 cu.m/sec the average flow velocity of 0.22 m/sec. The relatively low flow velocities obtained imply that —at least in "the vicinity of the experiment—the flow pattern is not materially influenced by faults and other tectonic features, but it implies at the same time that any significant reduction of inrush volumes can be expected only from grouting boreholes sunk in the immediate vicinity of the inrush point. BRIEF PUBLICATIONS AND REPORTS 1. Hernádi, A., Civ. and Mech. Engr.: Improvement of the flood levees on the Alargitta-sziget section (For the Hungarian text see pp. 259) Margitta island covering an area of 24.000 hectares protected by flood levees is situated in the southern part of Hungary, on the left-hand bank of the Danube, north of the Yugoslavian border. The flood plain was protected against inundation by the great flood of 1965, yet it demonstrated the weakness of the flood levees along the Danube. Therefore it was decided to reinforce the levees, calling for 3 million cu.m of earthmoving at a cost of 170 million Ft. Reinforcement work was started already after the ice-jam flood in 1956, in three stages illustrated in Fig. 1, of which stage A, the raising of the crest was completed by 1965. After 1965 it became imperative to urgently design new levee crosssections. The uniform shape (Fig. 2) can be attributed to "this urgency and fails to provide uniform security from the engineering point of view, owing to differences in foundation conditions and quality of material. In designing, the 48.25 km long section was divided into 8 parts (Fig. 3) of which construction work has been completed on 6, while it is still in progress on 2. In the early stages of construction difficulties have been encountered on account of the high moisture content of the soil, which surpassed 25%, whereas in later stages the soil could be placed at a moisture content of 15%. A relative density of 85% was specified and could be attained in general. Earthwork was accomplished using fleets of equipment based on scrapers and excavators as basic units (Figs. 5 to 7). Scrapers were used up to hauling distances of 1000 metres. The soil was deposited in 50 to 80 cm thick layers and was spread by bulldozers to 5 to 20 cm thickness. As far as density control is concerned, the Proctor test does not yield values sufficiently close to actual ones, since compaction by blows is used in the method, which occurs but infrequently. Isotope measurements alone do not appear to be sufficient, although a fair picture on scattering was obtained (Figs. 8 and 9). 2. Szilágyi, L., Civ. Engr. : Grass seeding with plastic foam (For the Hungarian text see pp. 269) After a review of experience gained with this method abroad, laboratory experiments have been performed by the Consulting Service for the Application of Plastics in Hydraulic Engineering, organized within the Research Institute for Water Resources Development, Budapest, in connection with the use of plastic foam for protecting grass seeds on the slopes of freshly completed embankments. A carbamideformaldehyde plastic foam of Hungarian manufacture was used for these experiments. In the course of biological tests the glass-pot experiments failed to yield the desired result, the seeds did not germinate. Two methods were tested for the use of plastic sheets: seeds were planted into a 5 cm thick foam layer, or the seeds were planted in soil and then covered by a 1 cm thick foam layer. The results of these experiments are tabulated in Table 1 and illustrated in Figs. 2 and 5). The germination percentage for seeds planted in the plastic foam sheet was higher and for monocotyledons than for dicotyledons. The specific cost of protection may be estimated at 6 to 7 Ft/sq.m. Field tests of a larger scale are contemplated in 1969. 3. Fehér, A., Civ. Engr. : Construction of diaphragm walls using coarse clay (For the Hungarian text see pp. 275) A requirement in the case of diaphragm walls serving as temporary cut-offs is that the permeability coefficient of the material placed under water "should not