Observation of shear zone development in ring-shear apparatus with a transparent shear box   总被引：1，自引：1，他引：1  

Hiroshi Fukuoka  Kyoji Sassa  Gonghui Wang  Ryo Sasaki 《Landslides》2006,3(3):239-251

Using a new ring-shear apparatus with a transparent shear box and video image analysis system, drained and undrained speed-controlled tests were conducted on coarse-grained silica sands to study the shear-zone formation process in granular materials. Velocity distribution profiles of grains under shear at various stages in the ring shear tests were observed through processing the video image by the Particle Image Velocimetry (PIV) program. Shear-zone thickness and type of shear mode (slide-like or flow-like) during shear were observed. Before reaching peak strength in low-speed and drained condition test, a comparatively major part of the sample in the upper shear box showed a velocity distribution profile of structural deformation and dilatancy behavior. After peak strength, the velocity profile changed into a slide-like mode and thereafter showed almost no change. In higher speed tests with drained and undrained conditions, an almost slide-like mode was observed, compared to low-speed test. Apparent shear-zone thicknesses of high-speed tests are thinner than low-speed tests. Unexpectedly, almost no difference was observed in the shear-zone thickness and mode of shear (slide or flow-like) between drained and undrained tests. This study was conducted as part of the International Programme on Landslides (IPL) M101 “Areal prediction of earthquake and rain induced rapid and long-traveling flow phenomena (APERITIF)” of the International Consortium on Landslides (ICL). These results will contribute to understanding the mechanism of shear-zone development in granular materials as a basic knowledge for disaster risk mitigation of rapid long run-out landslides.  相似文献   

Failure mechanism in an extremely slow rock slide at Bitchu-Matsuyama castle site (Japan)   总被引：1，自引：1，他引：1  

Vladimir Greif  Kyoji Sassa  Hiroshi Fukuoka 《Landslides》2006,3(1):22-38

One of the specific problems related to historical structures is the fact that they are prone to damage caused by even very small deformations acting over a long period of time, such as creep or extremely small rock displacements. If any damage has already occurred, the determination of the rock slope failure mechanism is one of the prerequisites for successful mitigation technique selection. In this study a medieval castle in central Japan, suffering damage caused by deformation of the rock mass in the subgrade of the castle, was investigated using a combination of field investigation, high-precision monitoring and physical modeling experiments. Using these techniques an attempt to determine the failure mechanism of the rock slope was made. Based on the field investigation a toe-slope failure seemed to be the main triggering factor activating the deformations in the upper slope area, right below the defense walls of the castle. The displacement monitoring of the surface rock blocks revealed a slumping failure with the backward rotational component prevailing over the sliding in the immediate vicinity of the castle wall. This was in accordance with the expectations obtained from the structural analysis of the rock mass carried out during the field investigation. The displacements obtained during the rock block monitoring, especially from the crack gauges, were not sufficient for drawing a satisfactory conclusions about the failure mechanism of the blocks located in the central part of the slope. Therefore, the failure mechanisms of rock blocks inferred from their displacements obtained from the monitoring were correlated with the results of modeling experiments carried out on the scaled slope model. The physical modeling revealed a possibility of toppling failure of rock blocks in the central area of the slope caused mainly by block interlocking, which was supported by the data from surface tilt meters installed additionally in the field. Furthermore, the possibility of the occurrence of forward and backward rock block rotations in the same sliding body at given conditions was supported by the physical modeling experiments.  相似文献   

Carbon and hydrogen isotope variation of plant biomarkers in a plant-soil system   总被引：2，自引：0，他引：2  

Yoshito Chikaraishi  Hiroshi Naraoka 《Chemical Geology》2006,231(3):190-202

Stable carbon (δ¹³C) and hydrogen (δD) isotopic compositions of n-alkanes, anteiso-alkanes, n-alkanoic acids, n-alkanols, phytol and sterols in raw leaves of Acer argutum and Acer carpinifolium, their fallen leaves, mold and soils from a natural Acer forest were measured in order to: (1) understand isotopic variation of the plant biomarkers in a plant-soil system and (2) evaluate which biomarker is the most effective recorder of soil vegetation. Long-chain (> C₂₄) n-alkanes, n-alkanoic acids and n-alkanols are gradually enriched in ¹³C up to 12.9‰ (average of 4.3‰) and depleted in D up to 94‰ (average of 55‰) from raw leaves to soils. However, anteiso-alkanes, phytol and sterols show little variation in both δ¹³C (< ± 1‰) and δD (< ± 2‰) from raw leaves to soils. These isotope signatures in a plant-soil system indicate that isoprenoid plant biomarkers such as sterols in soils faithfully preserve the isotopic compositions of dominant higher plants growing on the soils without a diagenetic effect upon the isotopic compositions. In contrast, long-chain n-alkyl molecules in soils undergo specific isotopic modification during biodegradation associated with early diagenesis and/or a significant contribution from heterotrophic reworking.  相似文献   

Irreversible thermodynamic and viscoelastic model for power-law relaxation and attenuation of rocks     

Yusuke Kawada  Hiroyuki Nagahama  Hiroaki Hara 《Tectonophysics》2006,427(1-4):255

A constitutive law for viscoelastic behaviour of rocks is derived from irreversible thermodynamics. To this model, two specific parameters are introduced; one is an internal state variable which is a variable concerning the microstructures such as defects in crystals or microcracks, and the other is a temperature reduced time obtained by normalizing the various temperature behaviours. A large number of internal state variables have the respective relaxation times and show the respective time evolutions, while a set of the time evolutions generates temporal power-law behaviour of rocks. The time evolutions of internal states are regarded as dynamics of elements of the generalized Maxwell model, and the stress–strain relation is represented by a response function following a temporal power-law in terms of linear system theory. This relation is inversely formulated to investigate the source field from output data. This model enables us to explain experimentally-based constitutive laws for transient and steady-state behaviour of rocks (e.g., lherzolite) following a temporal power-law and for attenuation behaviour of polycrystals (e.g., olivine) represented by a relation between the quality factor and frequency. Both laws show power-laws on deformation time or frequency depending on the fractal structure in polycrystals or rocks, and the experimental high-temperature behaviours can be extrapolated to long deformation time or high frequency behaviour.  相似文献   

Mesoscale spatial and temporal variability of meteorological observations from an array of buoys in JASIN-1978     

Hiroshi Ishida 《Boundary-Layer Meteorology》1986,37(1-2):149-165

Observations of wind speed and direction, air and sea temperatures and solar radiation were obtained from an array of buoys in JASIN-1978 conducted in the area northwest of Scotland in the summer of 1978. The observations were analyzed to show spatial and temporal variability in the mesoscale fields. Spectra of wind speed and air and sea temperatures were computed to illustrate the distribution of variance over periods ranging from 3.5 min to 40 days. When plotted on log-log graphs, the spectral estimates generally decreased with slopes between –3/2 and –2 with increasing frequency. Spectra of air and sea temperatures had a peak at the diurnal period but not the wind speed spectrum. When plotted in variance-preserving form, the spectrum of wind speed was consistent with a spectral gap and was qualitatively similar to other observations of low-frequency spectra. On the basis of auto- and cross-correlation analyses, it appeared that mesoscale eddies propagated through the array of buoys with the mean wind speed except during times of frontal passages. The cross-correlation between wind speed and air temperature showed evidence of horizontal roll vortices or some other forms of organized convection.  相似文献   

Noble gas elemental and isotopic abundances in deep-sea trenches in the western Pacific     

George Igarashi  Masako Kodera  Minoru Ozima  Yuji Sano  Hiroshi Wakita  Jacques Boulgue 《Earth and Planetary Science Letters》1987,86(1)

Noble gas elemental and isotopic abundances were measured in seven deep-sea water samples from five different sampling sites in the Nankai Trough, the Japan Trench and the Kuril Trench. The samples were obtained by the manned submersible “Nautile”. Most of the sampling sites are associated with clam colonies and/or fluid venting. Excesses both in³He/⁴He ratio and He concentration are observed in a seawater sample collected a few kilometers off the clam colonies which were found at a depth of 3830 m at the mouth of the Tenryu Canyon. Concentrations of noble gases (Ne, Ar, Kr and Xe) in this sample show progressive depletion from Ne to Xe relative to those in 1°C air-saturated seawater, which can be attributed to mixing of hot water ( 15°C) with cold ambient water ( 1°C). Isotopic compositions of Ne, Ar, Kr and Xe in this sample are atmospheric. These observations may reflect venting of hot pore water around the Tenryu Canyon. All the other samples show a significant excess in concentration of all noble gases relative to 1°C air-saturated seawater and the isotopic compositions are atmospheric. This excess of noble gas concentrations may appear to be air contamination in the samples. However, results of hydrocarbon analyses of the Kaiko samples imply that such large amount of air contamination is improbable. Decomposition of gas hydrate in deep-sea sediments is a more likely explanation for the observed excess of noble gas concentration.  相似文献   

Rare-earth distribution in alkali rocks from Oki-Dogo Island,Japan     

Hiroshi Nagasawa 《Contributions to Mineralogy and Petrology》1973,39(4):301-308

Rare-earth, Sr and Ba abundances were determined for three basalts, one mugearite, one trachyandesite and five trachytes from Dogo, Oki Islands, Japan and Ca-rich clinopyroxene and feldspar phenocryst samples separated from them. It is concluded that rareearth, Sr and Ba abundance patters for basalts and three trachytes could be explained by crystallization differentiation of olivine basalt magma, while those for other samples suggest more complicated process of magma production. Calculated Eu²⁺ to total Eu ratios in the magmas showed a increasing trend with differentiation. It is found that Yb and Lu partition coefficients were larger than those of lighter rare earths for clinopyroxenes in trachytes suggesting preferential substitution of the heavy rare-earth ions for Mg-site in the clinopyroxenes.  相似文献   

An ultimate steady-state pattern of c-axis fabric of quartz in metamorphic tectonites     

Dr. Ikuo Hara 《International Journal of Earth Sciences》1971,60(3):1142-1173

The c-axis fabrics of quartz grains at the hinge zones of the orthorhombic buckle folds of quartz-rich layers which were collected from the Sambagawa crystalline schists of Shikoku, Japan, have been described and discussed. Especially, attempt to correlate the pattern of the quartz fabric with the strain picture has been made. It has been pointed out that the high concentration of quartz axes on two positions which are symmetrically placed on the plane of the longest principal axis and the shortest principal axis of the strain ellipsoid and at an angle of ca. 30 to the latter axis may be regarded as an ultimate steady-state pattern of preferred orientation of quartz axes developed under non-rotational two dimensional strain.

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Zusammenfassung Untersucht wurden die Quarzachsen-Gefüge in den Scheiteln der orthorhombischen Biegefalten der quarzreichen Lagen aus dem Sambagawa-Schiefer von Shikoku, Japan. Besonders wurde es versucht, die Quarzachsen-Orientierung mit dem Verformungsbild zu vergleichen. Zwei Quarzachsen-Maxima in der Ebene von der lÄngsten Hauptachse und der kürzesten Hauptachse des Verformungsellipsoides, die symmetrisch zur kürzesten Hauptachse im Abstand von etwa 30 liegen, wurden als bevorzugte Endlagenorientierung der Quarzachsen angesprochen, die durch die zweidimensionale Verformung ohne Rotation erzeugt wurden.

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Résumé La fabrique c-axiale des grains de quartz dans les charnières de plis, collectionnés dans les schistes cristallins de Sambagawa prés de Shikoku (Japon) sont décrits et interprétés dans cette étude. Il a été essayé spécialement de comparer le type de la fabrique du quartz au type de la déformation. Enfin il a été prouvé que la forte concentration des axes de quartz en deux lieux fixes des diagrammes, qui sont situés symétriquement aux deux axes principaux (long et petit) de l ellipsoide de déformation et qui forment un angle de 30 avec le petit axe, sont les positions définitives et stables de l'orientation préférée des axes de quartz qui à été produite par une déformation bi-dimensionelle sans rotation.

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Sambagawa, Shikoku, . . , 30; , , .

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Precise temperature measurement of groundwater for earthquake-prediction study   总被引：2，自引：0，他引：2  

Yuji Nakamura  Hiroshi Wakita 《Pure and Applied Geophysics》1984,122(2-4):164-174

Precise measurements of groundwater temperature, with a resolution of 0.0001°C, have been made for the purpose of earthquake prediction at four water wells in the Tokai district in Japan. The characteristics of temporal variations in groundwater temperature differ from well to well. From records of a well located in an area where use of groundwater is heavy, movement of groundwater was sensed by temperature variations. By contrast, water temperatures in a 500 m well far from cultural areas were extremely steady, with fluctuations of less than 0.0005°C. This well appears to be suitable for monitoring possible temperature changes related to the occurrence of an impending large earthquake.  相似文献   

4439555 Antifouling composition     

Hiroshi Doi  Osamu Kadota  Susumu Kohno 《Marine pollution bulletin》1984,15(8):v-vi

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