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101.
将饱和砂土视为土水两相介质,以Biot动力固结方程为基础,编制了完全耦合的三维排水有效应力动力反应分析程序。利用该程序对碎石桩复合地基进行了动力反应分析。结果表明:在地震荷载作用下,碎石桩具有明显的减震效应,碎石桩复合地基表层的最大水平振动加速度与天然地基相比明显减小,并且碎石桩对地基的沉降变形有明显的抑制作用;碎石桩的排水效应十分显著,随着输入地震加速度的减弱,在孔压达到峰值以后,由下到上出现了明显的孔压消散现象,碎石桩排水效应的影响范围为上窄下宽的圆台形;碎石桩的加密效应显著;考虑碎石桩各效应的耦合作用比仅考虑其单一效应,计算得到的孔压比要小,因此在进行碎石桩复合地基抗液化判别时,应该综合考虑碎石桩各效应的相互耦合作用。 相似文献
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Based on high-resolution reanalysis data of the European Centre for Medium-Range Weather Forecasts, several samples of tropical cyclones (TCs), including tropical storms, severe tropical storms, and typhoons, in the South China Sea (SCS), were selected for composite analysis. The structures of these three types of vortices and their differences with ‘bogus’ vortices were investigated. Results showed that TCs in the SCS have characteristics that are distinctly different from vortices formed by the bogussing scheme used at Guangzhou Institute of Tropical and Marine Meteorology, such as no anticyclone in higher layers, strong convergence concentrated at the bottom of the troposphere, and strong divergence happening in higher layers instead of at 400 hPa. These differences provide clues for constructing a more realistic structure for TCs in the SCS. It was also found that the three types of vortices have some structural features in common. The area with high wind speed is fan-shaped in the north around the TC center, the maximum vorticity appears at 925 hPa, the strongest convergence appears at 1000 hPa, and strong divergence is located from 150 to 100 hPa. On the contrary, significant differences between them were revealed. The warm cores in tropical storms, severe tropical storms, and typhoons are located at 600–400 hPa, 400−300 hPa, and 400−250 hPa, respectively. Among the three types of TCs, the bogus vortex of tropical storms has the largest errors in structure and suffers the largest errors in track forecasts. However, typhoons have the largest errors in the forecast of intensity. This may be related to the great impacts of ocean on TC intensity. 相似文献
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本文对城市地震应急避难场所的建设现状和必要性进行了论述,分析计算了地震应急避难场所的类型,对地震应急避难场所编制内容及方法进行了探讨.同时以旺苍县城为例进行了详细分析.本文对提高城市综合防灾减灾能力有一定的参考意义. 相似文献
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Detrital zircon U–Pb LAM-ICPMS age patterns for sandstones from the mid-Permian –Triassic part (Rakaia Terrane) of the accretionary wedge forming the Torlesse Composite Terrane in Otago, New Zealand, and from the early Permian Nambucca Block of the New England Orogen, eastern Australia, constrain the development of the early Gondwana margin. In Otago, the Triassic Torlesse samples have a major (64%), younger group of Permian–Early Triassic age components at ca 280, 255 and 240 Ma, and a minor (30%) older age group with a Precambrian–early Paleozoic range (ca 1000, 600 and 500 Ma). In Permian sandstones nearby, the younger, Late Permian age components are diminished (30%) with respect to the older Precambrian–early Paleozoic age group, which now also contains major (50%) and unusual Carboniferous age components at ca 350–330 Ma. Sandstones from the Nambucca Block, an early Permian extensional basin in the southern New England Orogen, follow the Torlesse pattern: the youngest. Early Permian age components are minor (<20%) and the overall age patterns are dominated (40%) by Carboniferous age components (ca 350–320 Ma). These latter zircons are inherited from either the adjacent Devonian–Carboniferous accretionary wedge (e.g. Texas-Woolomin and Coffs Harbour Blocks) or the forearc basin (Tamworth Belt) farther to the west, in which volcaniclastic-dominated sandstone units have very similar pre-Permian (principally Carboniferous) age components. This gradual variation in age patterns from Devonian–late Carboniferous time in Australia to Late Permian–mid-Cretaceous time in New Zealand suggests an evolutionary model for the Eastern Gondwanaland plate margin and the repositioning of its subduction zone. (1) A Devonian to Carboniferous accretionary wedge in the New England Orogen developing at a (present-day) Queensland position until late in the Carboniferous. (2) Early Permian outboard repositioning of the primary, magmatic arc allowing formation of extensional basins throughout the New England Orogen. (3) Early to mid-Permian translocation of the accretionary wedge and more inboard active-margin elements, southwards to their present position. This was accompanied by oroclinal bending which allowed the initiation of a new, late Permian to Early Triassic accretionary wedge (eventually the Torlesse Composite Terrane of New Zealand) in an offshore Queensland position. (4) Jurassic–Cretaceous development of this accretionary wedge offshore, in northern Zealandia, with southwards translation of the various constituent terranes of the Torlesse Composite Terrane to their present New Zealand position. 相似文献