Vízügyi Közlemények, 1932 (14. évfolyam)

2. füzet - XII. Kisebb közlemények

29 then examines the gate still in a raised position, but this time taking into account the curvature of the downstream leaf, as well as the forces created by tightening the connecting chain (I'ig. 6) ; in this case the gate will appear as a beam of three hinges, the middle hinge being only imaginary. Finally he determines the water pressure which is needed for raising up the leaves from their recumbent position (Fig. 7). The examination of forces acting on the gate renders it possible to explain in detail the construction, the main parts of which are the upstream and the downstream leaves, and the piers or retaining walls confining the sides. The leaves consist of planks fastened to ribs placed in the form of a truss. The ribs are, on an average, 2-0 metres apart ; they are of solid section, seldom of lattice work. The section of the middle ribs, as well as the hinges and waterproofing features of the leaves are shown in Figure 8, wilst Fig. 9 represents the section of the outside ribs. Special features, by which the leaves can be kept in a raised position without internal water pressure, make it possible to repair them while the gate is in operation. Two different forms of these features are shown in Figures 11 and 12 ; the latter form lias the advantage of keeping the downstream leaf raised, as well as the other. The gate is raised by controlling the water level beneath the leaves ; for this purpose, besides the small sluice gates, auxiliary automatic controlling arrangements are used. (Fig. 13.) After explaining the details of the construction, the writer discusses the question of operation, the safety of which depends upon the behaviour of the dam towards detritus and ice. According to experiences obtained with Huber and Lutz bear trap dams, it may be stated that the sediment settled behind the dam can be easily cleared away by laying down the leaves. The only disadvantage of this is that from time to time the water has to be let out from beneath the leaves in order to wash out the fine sediment, since it may occur that after a certain time of operation the presence of the latter hinders the movement of the leaves. With regard to another important feature of operation, M. Geiss, Technical Councillor, has presribed the conditions to be observed, as follows : (1) the gate must be able to bear the impacts and pressure of drifted ice ; (2) the blocks of ice have to pass the gate without hindrance ; (3) moving parts of the dam should not be frozen to the piers and walls ; (4) if so, the actuating force must overcome the increased obstacles without any harm resulting to the dam. Considering these conditions, it may be stated that the bear trap dams comply with them satisfactorily, as has been proved in the hard winters of recent years. Though some difficulties occurred, owing to sludgy ice, there was no serious trouble in operation, whilst at the same time dams on other systems required considerable work to overcome difficulties caused by ice. VII. SOIL SURVEY AND MAPPING FOR THE PURPOSES OF RECLAMATION WORKS. Ну : LEO VAS. On the basis of a report by Dr. Ramsauer, submitted at a meeting of the International Soil Investigation Society held at Groningen in 1932, the writer