Vízügyi Közlemények, 1973 (55. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

The office buildings, transformer station, open switchyard associated with the barrage, as well as the homes of the operating personnel have been accommodated on the right-hand bank. The barrage is approached from Kisköre village by the access road constructed for this purpose. For providing rail connection during the construction period a side track had been branched off from the main line. The highest retention level envisaged is 91.20 m A.O.D., while the lowest, at complete drawdown of the impoundment, is 88.00 m A.O.D. At the barrage site the alluvial layers forming the foundation were deposited in the Pleistocene period of the geological Quaternary era. In the area explored the granular and cohesive layers alternate in the profile in accordance with the prevailing regime conditions. The cohesive strata immediately below the terrain vary from 5 to 13 m in thickness. This is underlain by a fine-sand layer of 8 to 15 m thickness interwoven with clayey silt lenticles and with very thin cohesive layers. The second cohesive layer containing silt and clay strata is from 4 to 10 m. At greater depths granular and cohesive layers were encountered alternatingly. The structures reach with their foundations well down into the first granular layer or to the vicinity of the top thereof. The groundwater table follows closely the fluctuations in river stage. The three principal structures of the barrage were built on the flood plain or the Tisza River in a common constuction pit protected from floods by a temporary ring dike. The pit had been excavated and the structures were built in the dry, after lowering the groundwater table in several stages. Two systems of groundwater lowering were considered more in detail, namely that by well points and the combination of well points and vacuum wells. In view of the highest differential head of 10.7 m and of the finegrained sand soil ready to flow, it was found necessary to prevent seepage under and around the structures, in order to avoid hydraulic soil failure and to reduce uplift forces. For this purpose an impervious reinforced-concrete cutoff wall was constructed on the upstream side by the slurry-trench method. The cutoff extends down into the second cohesive layer and provides at the same time support to the sides of the construction pit in the foundations of the structures. The lateral members of the cutoff wall serve also as the foundations of the retaining walls connecting to the structures. Each of the three main structures of the barrage are served by two derrick cranes of 40/10 ton capacity, travelling the length of the structure, which permit the placing of the emergency closures upstream and downstream of the power station, the mounting of turbines, placement and handling of the upstream- and downstream stop-log closures of the weiland the downstream stop-log closure of the navigation lock, as well as mounting the radial gates and the tilting leaves of the weir, further the mitre gate in the downstream head of the navigation lock. Internal traffic across the barrage and the operating cables, ducts are carried by a singlelane r.c. service bridge (Fig. 2.1—3). 269