Vízügyi Közlemények, 1959 (41. évfolyam)

4. füzet - V. Kisebb közlemények-Ismertetések

(10) вание пробивающих родников может быть давлением столба воды ликвидировано. Это однако можно применять только там, где покрывной слой имеет такую толщину, что элиминирует давления поступающие снизу вверх. Если толщина покрывного слоя так тон кая, что ее вес меньше давления воды, то на более значительных территориях необходимо парализовать снизу вверх поступающее давление перемычкой подпертой водой (рис. 21. —

1), или лучше предварительной погрузкой угрожаемой полосы (рис. 21. Ъ

—

2) или же уменьшением давления грунтовой воды помощью фильтрационных колодцев (рис, 21. Ъ

—3). (Резюме автора, перевод от инж. Г. Чегиди.) SAND BOILS AND HYDRAULIC SOIL FAILURE By H. Lampl Doctor of Technical Sciences (For the Hungarian text see pp. 25—49) UDC. 624.131.542 Boils, their development, together with the factors and conditions affecting their formation have been investigated within the framework of the inclusive flood protection research program carried out in the year 1957 at the Research Institute for Water Resources under the guidance of Air. D. Ihrig. Experiments were conducted with the aim to provide results that can be interpreted readily for practical purposes and that can offer useful information for those engaged in flood-protection activities about various stages of boil formation. The clearer insight into the causes of ruptures, that have occured in the Hungarian levee system during the floods of 1954 and 1956 i. e., into the soil failures resulted from the formation of boils, may contribute to the development of a system of protective measures against such contingencies. Equipment made especially for this purpose was used by the author for these laboratory experiments. Phenomena of upward seepage and flow through a 50 cm sq. cross section could be observed (Figs. 1 and 2). Cohesionless, granulated soils, susceptible to the formation of boils were used in the experiments. Gradation curves and physical properties of the experimental soils, denoted a, b, c, and d are shown and compiled in Fig. 4 and Tabic II, respectively. Experiments and investigations can be found grouped according to their respective aim and subject in Table I. Experiments carried out with differently graded, washed sands. Essentially three characteristic symptomatic stages could be observed during the development of boils and the subsequent soil failure : The first sgmptom being the occurrence of elementary boils which already cause the soil particles to move (Fig. 5), the second symptom being the appearance of the boils proper, where the emerging velocity of upward seeping flow attains, owing to the hydraulic pressure prevailing in the soil, a valu3 sufficiently high to dislocate the particles and to drag these upward, to be subsequently deposited in the form of a circular crater at the surface (Figs. (i. 7 and 8

) ; while the third symptom is the complete disturbance of the soil structure, i. e. hydraulic soil failure. Results obtained by differently, yet uniformly graded, washed sands—, denoted a, b, c and d

—as basic materials, have been entered into Fig. 10. As revealed by these experiments : f

. Elementary boils, actual boils and the usually subsequent soil failure occured, with granular cohesionless soils encountered in nature, at reasonably the same hydrostatic, head corresponding to a water column equal in height to the layer thickness in each particular experiment. 2. Permeability was found to affect no more than the quantity of seepage water emerging during unit time. 3. The specific weight of cohesionless, granulated soils encountered in nature varies between 2,6 and 2,7 g/cu.em and is of insignificant influence from the practical point of view.