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881.
There could be some discontinuities in a soil media such as layers, earth structures, cracks, and fissures so that estimation
of stresses and deformations in these types of soil masses are somewhat different from continuous masses. The discontinuities
in a soil mass could be considered as a special link between two blocks. Transmitted swelling pressures affected by the soil
properties of the backfill especially at the interface between the backfill and retaining wall. In order to estimate the transmitted
swelling pressure distribution behind a retaining wall, using with interface element, a new finite element model and a code
(SWELPRES) have been developed. To evaluate the effect of backfill characteristics and interface element from the transmitted
lateral swelling pressures, four cases of thickness of backfills with or without interface elements are investigated. 相似文献
882.
Eduardo E. Alonso Sarah M. Springman Charles W. W. Ng 《Geotechnical and Geological Engineering》2008,26(6):817-826
Two large-scale “in situ” demonstration experiments and their instrumentation are described. The first test (FEBEX Experiment)
involves the hydration of a compacted bentonite barrier under the combined effect of an inner source of heat and an outer
water flow from the confining saturated granite rock. In the second case, the progressive de-saturation of Opalinus clay induced
by maintained ventilation of an unlined tunnel is analyzed. The paper shows the performance of different sensors (capacitive
cells, psychrometers, TDR’s) and a comparison of fill behaviour with modelling results. The long term performance of some
instruments could also be evaluated specially in the case of FEBEX test. Capacitive sensors provide relative humidity data
during long transient periods characterised by very large variations of suction within the bentonite. 相似文献
883.
A numerical analysis of cyclotron instabilities is carried out by computing the dispersion relation for a three component cold plasma-beam system. Rates of growth and damping for various values of the stream density are calculated from the dispersion relation. The rates of growth and damping increase monotonically as the number density of the proton stream increases. It is found that the frequencies at the rates of maximum growth and the damping decrease slightly to lower frequencies and a sharp peak at these frequencies becomes blunt. The minimum e-folding times of an ion cyclotron wave for (a) σs = 10−4, σi = 10−2 and (b) σs = 10−1, σi = 10−2 are about 3·84 and 0·16 sec respectively in the vicinity of the equatorial plane at 6 Re, where σs and σi are the ratios of the beam density Ns and the helium ion (H6+) density Ni to the total positive ions in the plasma-beam system. 相似文献
884.
885.
The petrology of the East Otago Volcanic Province (late Miocene),including the Dunedin Complex, is dominated by undersaturatedsodic lavas and shallow intmsives whose compositions range fromalkali basalt, basanite, and nephelinite to trachyte and phonolite.A range of relatively potassic volcanic rocks is also developedin the Province. The degree of undersaturation and ratios suchas (FeO+Fe2O3):MgO and K2O:Na2O vary widely in rocks with comparabledifferentiation indices. Chemical and mineralogical data onwhole rock-glass pairs and variants of shallow intrusives inthe Province, assessed in conjunction with similar data fromother volcanic provinces, demonstrate the production of trachyticliquids from alkali basaltic parents and of phonolitic liquidsfrom basanitic parents. Fractionation trends in both sodic andpotassic series, defined by variation in differentiation indexand normative nepheline, indicate that the degree of undersaturationof the derivative salic liquids is dependent on that of theparent; the slope of the fractionation trend lines is influencedby additional factors, including Po2. The unequivocal productionof phonolite from trachyte in the East Otago Province has notbeen demonstrated. The mafic variants of theralites from Waihola and a basanite-pegmatoidassociation from Omimi are similar in composition, but the mostsalic differentiates from these differentiation sequences displaypronounced differences in their KO:Na2O ratios, tending towardsleuco-theralitic (cf. lugarite) and malignitic compositionsrespectively. A multicomponent spectrum of fractionation lineages is suggestedfor individual differentiated bodies and for lava series. Sodiclineages include: (I) alkali basalthawaiitemugearitebenmoreitetrachyte;(2) a more undersaturated series from basanite through nephelinehawaiite, nepheline mugearite, and nepheline benmoreite, tophonolite; (3) a nephelinite series, more restricted in compositionalrange. The relatively high Fe: Mg ratios characterizing themugearitic variants are sometimes exhibited by members of themore potassic series in which, however, Fe:Mg ratios tend tobe characteristically lower. This feature is correlated withthe frequent occurrence of kaersutitic amphibole or its resorptionproducts, indicative of intratelluric fractionation under relativelyhydrous conditions and probably relatively high Po2. Certainnepheline trachyandesites from East Otago are described in detail.Trachy-basalt-trachyandesite-tristanite-trachyte and sanidinebasanite-nepheline trachyandesite-nepheline tristanite-phonolitelineages are also proposed, and the nomenclature of these moreseries discussed. 相似文献
886.
887.
J. W. Norman 《The Photogrammetric Record》1968,6(32):133-149
The geologist's use of air photographs and the characteristics studied by photogeologists are briefly described. The influence of photographic factors such as scale, season, time of day, film type, processing, overlap and dimensional accuracy are considered from the geologist's viewpoint. 相似文献
888.
Photogrammetric methods using sequential aerial photography can provide the geomorphologist with comparative measurements of rapidly changing glacial landforms. Examples are given of eskers, kame and kettle areas, an ice-dammed lake and coastal features in south-east Iceland. 相似文献
889.
890.