Vízügyi Közlemények, 1973 (55. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

2.4 Koháry, N. and Nagy, I.: Construction work on earth canals and reservoirs (earthwork, structures) (For the Hungarian text, see pp. 115) A large portion of the area required for levee reinforcement was covered by forests, which had to be removed. Stumps smaller than 25 cm in diameter were dozed out by a bulldozer, for larger ones up to 80 cm in diameter either the scarifier shown in Fig. 2.4

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1 or the stump cutter shown in Fig. 2.4

—2 was used. Stumps larger than 80 cm in diameter were removed by blasting. The data of the reservoir embankments built in the first stage of construction are compiled in Table I, while the typical embankment crosssections are illustrated in Fig. 2.4

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9. For the embankment cores a relative density of 85%, while for the rest one of 80% modified Proctor value was specified. Field compaction supervision included conventional soil mechanical methods and the use of nuclear equipment. The earth was spread by scrapers in 20 to 30 cm thick layers and considerably precompacted in this process. Where necessary, additional compaction was performed by vibrating sheep-foot rollers. Parallel to embankment construction, the coarse profile of the cross-section was also shaped by crawler scrapers (Fig. 2.4—4). The trace of the main canals runs in plain, undrained areas, where groundwater levels are unfavourably high. The methods of construction were adopted accordigly. As a fundamental principle the structures were constructed first. The principal data of the main canals are compiled in Table II, the typical cross-sections and the method of construction being shown in Figs. 2.4

—5 and 2.4

—6. The impervious core of the canal embankments was raised 20 cm above the stationary water level, while the final crest is 1 m above this level. Pumping plants, levee-keepers' stations and maintenance centers have been erected along the reservoir embankments, intake- and surfaceregulating sluices on the main canals, and bridges or inverted siphons have ben constructed at crossings with existing roads, railways, irrigationand drainage canals. The number of such structures is in excess of 130. The main data of structures on the main canals have been compiled in Table III (see Figs. 2.4—7 and 2.4—8). The biological protecting system affords erosion control for the embankment slopes along the reservoir and the main canals and yields secondary agricultural benefits (Fig. 2.4

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9). For the water-side of various embankments plants preferring and tolerating moist conditions have been selected, while above the waterline and on the air-side grasses tolerating dry conditions have been planted. In order to preserve the nutritive power of the soil the application of different fertilizers is envisaged. The soil surface was first been harrowed, the grass seed was sown at the rate of 120 kg per hectare at a travelling speed of from 2 to 4 km per hour (Fig. 2.4—10). 277