Vízügyi Közlemények, 1971 (53. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(10) THE INFLUENCE OF SEEPAGE FLOW ON THE STABILITY OF GRANULAR LAYERS By Dr. Kovács, György (For the Hungarian text see pp. 9) When considering the influence of seepage flow on the stability of granular layers, the first step consists in classifying the phenomena caused by the scouring action of water penetrating the layer, by which the stability of individual grains, or group of grains is disturbed. The initial phase of the process consists of the scouring of the fine particles within the layer. The structure of the layer is rearranged thereby, or the fines are even scoured from the layer. An increase in the seepage velocity may already lead to the destruction of the skeleton formed by the coarse particles supporting each other, when the layer collapses, or a boil is formed. Once the equilibrium of a larger group of particles in the vicinity of the surface attains the boundary condition of stability and lability, hydraulic soil failure is imminent. Observing the above system of classification, the publications in the relevant literature describing individual processes are reviewed. This is supplemented by the results of a few more recent theoretical investigations and finally a uniform computation method is recommended for determining the data serving for the description of various phases. Concerning the scouring of fine particles it is first necessary to decide, whether the layer tends at all to suffosion, or the size of the fines and the shape of their grain size distribution curve precludes basically the movement of fines, i.e., the layer may be regarded as self-filtering. The comparison and improvement of the methods suggested for the determination thereof permitted to suggest for this investigation a method which is also theoretically well founded, and offers at the same time the possibility for drawing the boundary between suffosion and the collapse of the layer. The next value to be determined is the critical velocity initiating the scouring of fine particles. The relevant observations are rather incomplete, so that no computation method can be given. However, taking the continuously acting factors into consideration a program of future experiments could be outlined. Relying on earlier investigations on hydraulic soil failure relationships of general character could be derived which yield information on the stability of both horizontal and sloping surfaces. Supplementing these, earlier investigations were completed by a method serving to allow also for rock stresses. In fact this influence is great enough to be included in the case of vertical boundaries (e.g. the study of well filters). In conclusion relationships are suggested for computing the data of gravel filters offering protection from suffosion and hydraulic soil failure. CONTROL OF OPEN-CANAL IRRIGATION SYSTEMS AND THE CONSTRUCTION OF ANNUAL AND PERSPECTIVE OPERATION SCHEDULES ON THE BASIS OF METEOROLOGICAL DATA By Dr. Deseö, Dénes (For the Hungarian text see. 31) The Tiszalök irrigation system, commissioned in 195G has been converted to upstream conrolled operation, obliging farmers to announce their water demands three days in advance. The records for the first years indicated the existence of a relationship between the diverted rates of discharge and the daily meteorological elements, such as the daily