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Tsutomu Namikawa 《国际地质力学数值与分析法杂志》2001,25(6):605-627
A delayed plastic model, based on the theory of plasticity, is proposed to represent the time‐dependent behaviour of materials. It is assumed in this model that the stress can lie outside the yield surface and the conjugate stress called static stress is defined on the yield surface. The stress–strain relation is calculated based on the plastic theory embedding the static stress. Thus, the stress–strain relation of the model practically corresponds to that of the inviscid elastoplastic model under fairly low rate deformation. The delayed plastic model is coupled with the Cam‐clay model for normally consolidated clays. The performance of the model is then examined by comparing the model predictions with reported time‐dependent behaviour of clays under undrained triaxial conditions. It is shown that the model is capable of predicting the effect of strain rate during undrained shear and the undrained creep behaviour including creep rupture. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Tomikazu Namikawa Hiromitsu Hamabata Yasusi Hosoya S. Matsushita 《Planetary and Space Science》1983,31(8):913-921
Propagation characteristics of hydromagnetic waves in a cold plasma mixed with a hot plasma under a uniform static magnetic field are investigated. The existence of cold plasma seriously affects the polarization properties of the waves. The results are applied to the interpretation of Pcl and Pc5 with righthand polarizations guided along the geomagnetic field line. 相似文献
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This paper presents an elasto‐plastic model for non‐linear analyses of cement‐treated sand. Various laboratory tests were systematically carried out to investigate the pre‐peak and post‐peak behaviours of a cement‐treated sand. On the basis of these experimental results, the new model was built within the framework of a relatively simple elasto‐plastic theory. Two failure criteria are employed to express tensile and shear failure characteristics observed in the experimental results of the cement‐treated sand. The proposed model can describe strain‐hardening and strain‐softening responses under both failure modes. In the strain‐softening rules, the smeared crack concept is used, and a characteristic length is considered to avoid the issue of mesh‐size dependency. Since the failure criterion and strain‐hardening/softening rules are based on the experimental evidences, the model is relatively easy to understand and the parameters used in the model have clear physical meaning. The proposed model was applied to simulate the behaviour of cement‐treated sand in various laboratory tests, allowing for a reasonable comprehensive evaluation. It was demonstrated that the proposed model is suitable for describing both the tensile and shear failure behaviours of cement‐treated sand. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Esperanza Muñoz-Salinas C. S. Renschler D. Palacios L. M. Namikawa 《Natural Hazards》2008,45(2):309-320
In contrast to dramatic flow regime changes by less frequent large-scale volcanic eruptions, those caused by more frequent
small-scale processes in volcanic landscapes may also drastically change the direction and dynamics of flow in a drainage
system formed solely by fluvial processes. During such periods of channel morphology change, it is necessary to frequently
update channel flow parameters to assess preventive measures for civil protection purposes. Often aerial photography is impracticable,
since parts of the channels are covered by dense vegetation, while total station and laser topographic surveys are often too
slow and costly, particularly during a high frequency of events. This article introduces and validates a new methodology for
updating the representation of channel morphology in Digital Elevation Models (DEM) used specifically for assessing the dangers
of frequently occurring lahars along gorges in volcanic landscapes during eruptive and non-eruptive periods. The updating
of channel cross-sections was achieved by inserting more detailed representative profiles of homogeneous channel sectors in
DEMs derived from existing less detailed topographic maps. The channel profiles were surveyed along the thalweg in equidistant
points according to Universal Transverse Mercator (UTM) (x,y) coordinates and elevation derived from the existing DEM. The
proposed technique was applied at Tenenepanco-Huiloac Gorge on Popocatépetl volcano, Mexico, in an area affected by major
lahars during the volcano’s most recent eruptive period from 1994 to 2005. The proposed method can reduce the cost and person-hours
of a regular channel topographic survey dramatically and the enhanced DEM can determine volume parameters and flood zones
associated with the 1 July 1997 and 21 January 2001 lahars, respectively. In addition, the updated DEM with better channel
representation allowed a more realistic fluid flow and lahar simulation with the process-based TITAN2D model. 相似文献
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Propagation characteristics of hydromagnetic waves in a hot plasma are investigated and the results are used to the interpretation of Pc1 and Pc5 with right-hand polarization guided along the geomagnetic field line. 相似文献
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