Vízügyi Közlemények, 1970 (52. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(29) EXPERIENCES GAINED DURING THE REINFORCEMENT OF LEVEES ALONG THE RÁBA RIVER BY THE HYDRAULIC FILL METHOD By L. Böcskei, Mech. Engr. and B. Ilajós, Civ. Engr. (for the LIungarian text see pp. 152). On the basis of experiences gained during the floods in tiie past decades largescale reinforcement work was started in September, 1969, on the levees along the lower reach —between Árpás and Győr —of the Rába River in the western part of Hungary, flowing from the south to the north and discharging at Győr into the Danube (Fig. 1 ). During these operations the crest of the levees was raised and the cross-section enlarged. Reinforcement work on the cross-Section is performed in the technological sequence illustrated in Fig. 2. The granular material required for the air-side protecting fill amounts to round 2.2 million cu.m and is obtained by suction dredge-work from the bed of the Rába River. The principal unit in the set of equipment is the floating Suction dredge of the type Master, manufactured by 111C, Holland ( Fig. 3). The first operation consists of stripping from the landside slope the topsoil and using this material for the dikes of the settling basin. The cohesive material necessary for raising the crest is displaced next. The settling space thus formed is ready to receive the material discharged through a pipeline from the dredge (Fig. 5). The arrangement of the pipeline is shown in Fig. 6 and the method of filling in Fig. 7. The attendant pipe-laying work was taken care of by two labour teams, each consisting of 8 labourers, assisted by the hoist Shown in Fig. 7. Depending on the drainage opportunities controlled by Site conditions one of the three operating methods shown in Fig. !) was applied. The numbering indicates the Sequence in which the fields are filled. In the case of single-end drainage illustrated in Fig. 9c temporary cross dikes are used to prevent flooding of the entire settling area prepared ( Fig. 10). The settled material is used for the Supporting filter body of the levee, which is then covered by the original topsoil forming the dikes. Bulldozers are used for this work, with the exception of sections where former channels are crossed, where an excavator is employed (Fig. 12). With the construction method described reinforcement of the right-hand bank levees has been completed up to station 6 + 00 km. A view of the finished levee is shown in Fig. 13. The grain-size distribution curve of the material transported is to be seen from Fig. 14. Besides dredging time was spent on the removal of boulders, the inoperative hours being indicated in Tabic 1. The abrasive effect of the Slurry is illustrated in Figs. 15, 16, the numerical data on wear compiled in Tabic II. The composition of the alloying materials of the cast pump casings is Shown in Table 111. The texture of the material of the pump casing SZH 2 can be seen in Fig. 17. The Service life of pump casings —in hours—together with the measures taken in order to ensure continuous operation is summarized in Tabic IV. The typical wear of the impeller, which is believed to be due to the assymmelry of the flow pattern is illustrated in Fig. 18. The advantage of the method of construction described is that no right-of-way costs and damages are charged against reinforcement work and no gaping borrow pits are left behind. At the Same time, construction work is largely unaffected by weather and flow regime in the river. RELATIONSHIP BETWEEN FLOW CONDITIONS AND BEI) CONFIGURATION By Dr. L. Ivicsics, Civ. Engr. (For the Hungarian text see pp. 141) Knowledge and experience available on the relationship between flow conditions and the channel configuration of movable bed watercourses are Summarized. The typical flow patterns pertaining to particular types of bed change are