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21.
A method for analyzing the earthquake response of elastic, cylindrical liquid storage tanks under vertical excitations is presented. The method is based on superposition of the free axisymmetrical vibrational modes obtained numerically by the finite element method. The validity of these modes has been checked analytically and the formulation of the load vector has been confirmed by a static analysis. Two forms of ground excitations have been used: step functions and recorded seismic components. The radial and axial displacements are computed and the corresponding stresses are presented. Both fixed and partly fixed tanks are considered to evaluate the effect of base fixation on tank behaviour. Finally, tank response under the simultaneous action of both vertical and lateral excitations is calculated to evaluate the relative importance of the vertical component of ground acceleration on the overall seismic behaviour of liquid storage tanks. 相似文献
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On the 21st of June, 1982, Mt. Niragongo ended a period of dormancy that had begun on January 11, 1977, and fresh lava began to flow into the 800-m-deep crater. On October 3, a huge lava lake, wider and deeper than any previously observed (500 m across and close to 400 m deep) rose to within 440 m of the crater rim. The observed activity consisted of a large, central upwelling fountain of very fluid lava from which concentric lava waves expanded radially; numerous small, relatively viscous lava flows creeped over the surrounding thin solidified crust, that covered about 95% of the lake area. These observed features seem to characterize the upper part of a large convective system. The persistence of such an extraordinarily large steady-state lava lake may be due to the equally exceptional fluidity of the magma rising at the intersection of four different tectonic trends of fractures in the subvolcanic basement. 相似文献
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Haroun Tazieff 《International Journal of Earth Sciences》1972,61(2):470-480
Hyoclastites mainly result from underwater comminution of molten basalts initially explosively erupted out of the sea-floor and instantaneously pulverized by closely succeeding phreatic explosion (s).Many sea-mounts probably never were the alleged volcanic islands, later sea-level eroded into truncated cones and eventually drowned several km down, they are claimed to be. They are here considered as submarine polygenic volcanoes, the shape of which is congenital. Their building up probably started by accumulation of numberless flows of basalt, quietly poured out from a long-lived central vent; when this lava-volcano's crater, so progressively carried higher and higher, reached depths where explosive phenomena became possible because of lowered hydrostatic pressure, magmatic explosions occurred due to violent release of primitively dissolved (or combined) gases. Shattering of lava, 1) increases by several orders of magnitude lava's surface to volume ratios, so allowing huge quantities of super-heated steam to be engendered; 2) this super-heated steam trapped below the lava-lumps, as well as in their numberless holes, immediately explodes and comminutes the primary lavalumps; 3) so other super-heated steam is produced and further steam explosions are resumed in confined room until almost all the primitive heat content of the magma is transformed into kinetic energy and the lava is comminuted into glassy, ashy, hyaloclastites.This process also works above fissural eruptions. The difference is that fissural volcanoes, contrarily to large central ones, are usually monogenic (i. e. delivering one eruption only through the same vent instead of numberless ones for polygenic volcanoes). Linear effusive eruptions also produce quietly flowing basaltic flows but — because being monogenic — they cannot build up big, and eventually steep, reliefs as polygenic volcanoes do. When not poured over steep slopes where pillowlavas develop, submarine flows are characterized by 1) the lack of any scoriaceous, more or less thick, upper part (or jacket), and 2) a regular pavingstone-like surface, each polygon of which being the upper face of short prisms similar to ordinary columnar prismation, but one or two orders of magnitude shorter. As for central volcanoes, explosive activity along submarine fissures produces huge quantities of hyaloclastites, but these cannot be heaped up into steep ridges, as happens for subglacial eruptions, because sea-currents spread them far and wide.
Zusmmenfassung Die Hyaloclastiten entstehen hauptsächlich durch submarines Zerspratzen von Lava, die bei vulkanischen Explosionen im Meer ausgeworfen wurde.Zahlreiche sea-monts waren wahrscheinlich niemals vulkanische Inseln, die später abgestumpft und überschwemmt wurden, wie es allgemein angenommen wird. Wir sind überzeugt, daß ein großer Teil der Vulkane sich unter Wasser gebildet hat aus Laven, die aus einem langlebigen Zufuhrkanal gefördert wurden und die allmählich nach oben wuchsen.Die Bildungsart der Hyaloclastiten, die hier beschrieben wird, erklärt die Tafelformen und die aus Palagonit bestehenden zackigen Berggrate, die Islands Unter-Eis-Vulkanismus kennzeichnen.
Résumé Les hyaloclastites (palagonites) sont formées essentiellement par la fragmentation en milieu aqueux des lambeaux de lave lancés par explosions volcaniques sous-marines (ou sous-lacustres ou sous-glaciaires). Cette fragmentation résulte de l'explosion de la vapeur prisonnière dans et sous les dits lambeaux.Beaucoup de guyots (sea-mounts) n'ont probablement jamais été, comme on le croit généralement, des îles volcaniques ultérieurement tronquées par érosion et englouties. Nous sommes convaincus qu'une forte proportion de guyots sont des volcans sous-marins, faits de coulées interstratifiées avec des hyaloclastites, et que leur forme tronconique est congénitale.Le processus de formation des hyaloclastites que nous décrivons rend compte également des montagnes tabulaires et des crêtes dentelées, constituées de palagonites, caractéristiques du volcanisme sous-glaciaire d'Islande.Les coulées subaquatiques subhorizontales offrent une surface polygonale de « basaltes en pravés ».
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Models of two-dimensional x-braced elevated tanks supported on isolated footings are analyzed to investigate the effects of dynamic interaction between the tower and the supporting soil-foundation system. Static, dynamic elastic, and dynamic inelastic responses of towers under horizontal ground motions are evaluated. Effects of soil properties, represented by the shear wave velocity, on joint displacements and on member end actions are studied. In general, soil-tower interaction reduces member end actions except near the base of tower. 相似文献
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Franois Le Guern Haroun Tazieff Camille Vavasseur Pierre Zettwoog 《Journal of Volcanology and Geothermal Research》1982,12(1-2)
During 1968–1969 the “Bocca Nuova”, a small vent, 7 m across, located in the northern part of Mt. Etna's summit crater showed a resonating-pipe phenomenon triggered by explosions at its bottom. The emitted gases were mixed with air. Temperatures, velocities, dynamic pressures and CO2 and N2 contents, were recorded. 相似文献
27.
Medhat A. Haroun 《地震工程与结构动力学》1983,11(2):179-206
Theoretical and experimental investigations of the dynamic behaviour of ground-supported, deformable, cylindrical liquid storage tanks were conducted. The study was carried out in three phases: (I) a detailed theoretical treatment of the coupled liquid-shell system for tanks rigidly anchored to their foundations; (II) an experimental investigation of the dynamic characteristics of full-scale tanks; and (III) a development of an improved seismic design procedure. 相似文献
28.
Mabrouk SAMI Theodoros NTAFLOS Haroun A. MOHAMED Esam S. FARAHAT Christoph HAUZENBERGER Nasser M. MAHDY Khaled M. ABDELFADIL Douaa FATHY 《《地质学报》英文版》2020,94(3):763-776
A highly-fractionated garnet-bearing muscovite granite represents the marginal granitic facies of the Abu-Diab multiphase pluton in the Central Eastern Desert of Egypt. New electron microprobe analyses(EMPA) and laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) data from garnets are reported, in order to constrain their origin and genesis. Garnet in the Abu-Diab host granite is euhedral to subhedral, generally homogeneous and, in rare cases, it shows weak zonation. The garnet contains appreciable amounts of MnO and FeO, with lesser amounts of MgO and CaO, yielding an end-member formula of Sps_(61–72)Alm_(25–35)Prp_(1–4)Adr_(0–1). Moreover, it is depleted in large ion lithophile elements(LILE) with lower values of Ba, Nb and Sr relative to the primitive mantle. Additionally, it contains high concentrations of HREE and Y and their REE pattern shows strong negative Eu anomalies. The garnet was crystallized under relatively low temperature(646°C–591°C) and pressure( 3 kbar) conditions. The textural and chemical features indicate that the garnet is magmatic in origin and is chemically similar to that from highly-fractionated A-type granite. It was probably formed at the expense of biotite in a highly-evolved MnO-rich magma and/or by hydroxyl complexing of Mn during the ascending fluid phases. 相似文献
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