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121.
The static, cyclic, and dynamic response of a massive caisson foundation embedded in nonlinear layered or inhomogeneous soil and loaded at its top is investigated. The caisson is supported against horizontal displacement and rotation by four types of inelastic springs and dashpots, described with the BWGG model that was developed in the preceding companion paper [Gerolymos N, Gazetas G. Development of winkler model for static and dynamic response of caisson foundations with soil and interface nonlinearities. Soil Dyn Earthq Eng, submitted companion paper]. The prediction of the model is satisfactorily compared with results from 3D-finite element analysis. Some experimental corroboration of the method is provided with the help of a 1/3-scale lateral load test that had been conducted in the field by EPRI. An illustrative example of a caisson embedded in linearly-inhomogeneous clay and subjected to static and dynamic loading is analysed. Characteristic results are presented highlighting the role of soil inelasticity and its interplay with the two dominant interface nonlinearities: separation (gapping) of the caisson shaft from the surrounding soil, and uplifting of the base from the underlying soil. 相似文献
122.
波动方程叠前深度偏移在地震勘探成像处理方面起着不可替代的作用。随着高性能大规模并行计算机技术的发展,波动方程叠前深度偏移计算在地震勘探中的应用有了很大进步。在波动方程叠前深度偏移处理中,庞大的数据规模与海量计算对计算性能提出了很高的要求。曙光4000A超级计算机系统是我国目前峰值速度最快的商用超级计算机系统,无论是硬件平台建设还是应用软件的配置方面,都具有良好的应用性能。基于该系统设计的三维波动方程叠前深度偏移(炮域)PSDM软件,采用动态负载平衡并行计算模式,具有较高的计算效率,高度的可扩展性和可靠性。 相似文献
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南京红层岩性复杂,桩基持力层承载力难确定。依据南京某工程勘察资料,建立南京红层泥岩、泥质粉砂岩不同互层情况的地质模型,运用FLAC3D软件分析,并与载荷板试验结果进行对比表明:桩基持力层应选择在厚度大于两倍桩径的泥质粉砂岩地层上,避免放置于泥岩地层;载荷板试验结果偏于保守,设计时可以把这部分作为安全储备。 相似文献
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Volcanic lightning, perhaps the most spectacular consequence of the electrification of volcanic plumes, has been implicated in the origin of life on Earth, and may also exist in other planetary atmospheres. Recent years have seen volcanic lightning detection used as part of a portfolio of developing techniques to monitor volcanic eruptions. Remote sensing measurement techniques have been used to monitor volcanic lightning, but surface observations of the atmospheric electric Potential Gradient (PG) and the charge carried on volcanic ash also show that many volcanic plumes, whilst not sufficiently electrified to produce lightning, have detectable electrification exceeding that of their surrounding environment. Electrification has only been observed associated with ash-rich explosive plumes, but there is little evidence that the composition of the ash is critical to its occurrence. Different conceptual theories for charge generation and separation in volcanic plumes have been developed to explain the disparate observations obtained, but the ash fragmentation mechanism appears to be a key parameter. It is unclear which mechanisms or combinations of electrification mechanisms dominate in different circumstances. Electrostatic forces play an important role in modulating the dry fall-out of ash from a volcanic plume. Beyond the local electrification of plumes, the higher stratospheric particle concentrations following a large explosive eruption may affect the global atmospheric electrical circuit. It is possible that this might present another, if minor, way by which large volcanic eruptions affect global climate. The direct hazard of volcanic lightning to communities is generally low compared to other aspects of volcanic activity. 相似文献
128.
Karen L. Aplin 《Surveys in Geophysics》2006,27(1):63-108
Atmospheric electrification is not a purely terrestrial phenomenon: all Solar System planetary atmospheres become slightly
electrified by cosmic ray ionisation. There is evidence for lightning on Jupiter, Saturn, Uranus and Neptune, and it is possible
on Mars, Venus and Titan. Controversy surrounds the role of atmospheric electricity in physical climate processes on Earth;
here, a comparative approach is employed to review the role of electrification in the atmospheres of other planets and their
moons. This paper reviews the theory, and, where available, measurements, of planetary atmospheric electricity which is taken
to include ion production and ion–aerosol interactions. The conditions necessary for a planetary atmospheric electric circuit
similar to Earth’s, and the likelihood of meeting these conditions in other planetary atmospheres, are briefly discussed.
Atmospheric electrification could be important throughout the solar system, particularly at the outer planets which receive
little solar radiation, increasing the relative significance of electrical forces. Nucleation onto atmospheric ions has been
predicted to affect the evolution and lifetime of haze layers on Titan, Neptune and Triton. Atmospheric electrical processes
on Titan, before the arrival of the Huygens probe, are summarised. For planets closer to Earth, heating from solar radiation
dominates atmospheric circulations. However, Mars may have a global circuit analogous to the terrestrial model, but based
on electrical discharges from dust storms. There is an increasing need for direct measurements of planetary atmospheric electrification,
in particular on Mars, to assess the risk for future unmanned and manned missions. Theoretical understanding could be increased
by cross-disciplinary work to modify and update models and parameterisations initially developed for a specific atmosphere,
to make them more broadly applicable to other planetary atmospheres. 相似文献
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