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931.
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Zhu Yu Wei Jun Yang Manjuan Li Hao Liu Hongqing 《中国地质大学学报(英文版)》2005,16(3):277-282
INTRODUCTION Tunnel typeanchoragehasobviousadvantages inbearingcapacityversusinvestment(LiuandHu,1996).However,itisrarelyusedinapracticalpro jectbecauseofitsrequirementofgoodrockcondi tions.Siduhebridge(Fig.1),whichliesintheBa dongmountainsinthewestplatea… 相似文献
934.
The conventional interpretation methods of pressuremeter testing effectively approximate pressuremeter membranes as infinitely long. As a result, the effects of the two‐dimensional geometry of pressuremeters are ignored, leading to an overestimation of soil shear strength by pressuremeter testing, as demonstrated in several previous studies. This paper presents results of a numerical study of two‐dimensional geometry effects on self‐boring pressuremeter tests in undrained clay. The results are obtained using critical state soil models with an effective stress formulation. This is in contrast to most (if not all) existing studies on pressuremeter geometry effects, which were based on perfectly plastic soil models (e.g. Yu (Cavity expansion theory and its application to the analysis of pressuremeters. DPhil Thesis, The University of Oxford, 1990), Yeung and Carter (Proc. 3rd Int. Symp. on Pressuremeters, 1990), and Houlsby and Carter (Géotechnique, 1993; 43 (4):567–576)). The present study suggests that the overestimation of soil strength due to the neglect of finite pressuremeter length is significantly affected by the soil model used in the calculations. It is found that for clays with a high overconsolidation ratio (OCR) the strength overestimation predicted using critical state soil models could be considerably smaller than that predicted using perfectly plastic soil models. The main conclusion of this numerical study is that care must be exercised before directly applying any numerically determined pressuremeter geometry correction factors in practice. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Fe L-, S L-, and O K-edge X-ray absorption spectra of natural monoclinic and hexagonal pyrrhotites, Fe1-xS, and arsenopyrite, FeAsS, have been measured and compared with the spectra of minerals oxidized in air and treated in aqueous acidic solutions, as well as with the previous XPS studies. The Fe L-edge X-ray absorption near-edge structure (XANES) of vacuum-cleaved pyrrhotites showed the presence of, aside from high-spin Fe2+, small quantity of Fe3+, which was higher for a monoclinic mineral. The spectra of the essentially metal-depleted surfaces produced by the non-oxidative and oxidative acidic leaching of pyrrhotites exhibit substantially enhanced contributions of Fe3+ and a form of high-spin Fe2+ with the energy of the 3d orbitals increased by 0.3–0.8 eV; low-spin Fe2+ was not confidently distinguished, owing probably to its rapid oxidation. The changes in the S L-edge spectra reflect the emergence of Fe3+ and reduced density of S s–Fe 4s antibonding states. The Fe L-edge XANES of arsenopyrite shows almost unsplit eg band of singlet Fe2+ along with minor contributions attributable to high-spin Fe2+ and Fe3+. Iron retains the low-spin state in the sulphur-excessive layer formed by the oxidative leaching in 0.4 M ferric chloride and ferric sulphate acidic solutions. The S L-edge XANES of arsenopyrite leached in the ferric chloride, but not ferric sulphate, solution has considerably decreased pre-edge maxima, indicating the lesser admixture of S s states to Fe 3d orbitals in the reacted surface layer. The ferric nitrate treatment produces Fe3+ species and sulphur in oxidation state between +2 and +4. 相似文献
937.
We estimate the absolute intensity of the Hα emission line in M17 based on spectroscopic observations with the 70 cm telescope of the Fesenkov Astrophysical Institute and the 1.25 m telescope of the Sternberg Astronomical Institute’s Crimean Laboratory. The visual extinction, A v , is derived for about 250 regions in the nebula via a comparison of the optical (Hα) and radio (21 cm continuum) emissions. The A v values for the eastern, optically bright, part of the nebula are 2–6m. For the western part, which is covered by a dark cloud, the extinction is A v = 7?14.5m. We derived I(Hα)/I([NII] λ6584) ratios and estimated the degree of ionization of nitrogen in the nebula; we find that most nitrogen is in the [NIII] state. 相似文献
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