A diametral deformation method forin situ stress and rock property measurement     

Shosei Serata  Shinji Kikuchi 《Geotechnical and Geological Engineering》1986,4(1):15-38

Summary Failure deformation of a borehole boundary in response to hydraulic loading via a plastic cylinder is directly related to both the initial stress state and the material properties of the ground. These relationships are utilized for determination ofin situ stress states and material properties of complex geological formations, including fractured hard rock and soft ductile media, by directly measuring diametral deformation of the borehole in relation to the applied pressure. This new method was first developed by means of finite element simulation models, and later confirmed by laboratory model studies. This method was then field tested in an outcropping of homogeneous sandstone and later applied to three underground geological formations: highly stratified shale, rock salt, and fractured green schist. Some of the results of these field applications are presented here to illustrate the validity and usefulness of this method, especially for complex ground where the conventional methods of overcoring and hydrofracturing may be ineffective. The instrumentation of this method involves a borehole probe which utilizes electrically powered hydraulic pumping and computerized data acquisition for rapid measurement and on-site analysis. The significance of the new method is its ability to obtain input data ofin situ stress states and material properties for finite element analysis of earth structures in complex ground.  相似文献   

Pyroclastic flows from the 1991 eruption of Unzen volcano,Japan   总被引：1，自引：0，他引：1  

Takahiro Yamamoto  Shinji Takarada  Shigeru Suto 《Bulletin of Volcanology》1993,55(3):166-175

Pyroclastic flows from Unzen were generated by gravitational collapse of the growing lava dome. As soon as the parental lobe failed at the edge of the dome, spontaneous shattering of lava occurred and induced a gravity flow of blocks and finer debris. The flows had a overhanging, tongue-like head and cone- or rollershaped vortices expanding outward and upward. Most of the flows traveled from 1 to 3 km, but some flows reached more than 4 km, burning houses and killing people in the evacuated zone of Kita-kamikoba on the eastern foot of the volcano. The velocities of the flows ranged from 15 to 25 m/s on the gentle middle flank. Observations of the flows and their deposits suggest that they consisted of a dense basal avalanche and an overlying turbulent ash cloud. The basal avalanche swept down a topographic low and formed to tongue-like lobe having well-defined levees; it is presumed to have moved as a non-Newtonian fluid. The measured velocities and runout distances of the flows can be matched to a Bingham model for the basal avalanche by the addition of turbulent resistance. The rheologic model parameters for the 29 May flow are as follows: the density is 1300 kg/m³, the yield strength is 850 Pa, the viscosity is 90 Pa s, and the thickness of the avalanche is 2 m. The ash cloud is interpreted as a turbulent mixing layer above the basal avalanche. The buoyant portions of the cloud produced ash-fall deposits, whereas the dense portions moved as a surge separated from the parental avalanche. The ash-cloud surges formed a wide devastated zone covered by very thin debris. The initial velocities of the 3 June surges, when they detached from avalanches, are determined by the runout distance and the angle of the energy-line slope. A comparison between the estimated velocities of the 3 June avalanches and the surges indicates that the surges that extended steep slopes along the avalanche path, detached directly from the turbulent heads of the avalanches. The over-running surge that reached Kita-Kamikoba had an estimated velocity higher than that of the avalanche; this farther-travelled surge is presumed to have been generated by collapse of a rising ash-cloud plume.  相似文献   

Automatic extraction of lineament information from satellite images using digital elevation data   总被引：1，自引：0，他引：1  

Venkatesh Raghavan  Kiyoshi Wadatsumi  Shinji Masumoto 《Natural Resources Research》1993,2(2):148-155

Using conventional visual interpretation in lineament analysis presents two main problems. The first is subjectivity, introduced because of the bias of various interpreters. The second problem is that lineaments detected from satellite images are constrained by the direction of the illumination source. Since lineament identification mainly involves recognition of diagnostic morphological features, the use of digital elevation can contribute significant information about these features. Further, in generating images using digital elevation data, the direction of illumination can easily be controlled. Thus, the use of digital elevation data offers the possibility of revealing features not apparent in regular satellite images.We discuss a sequential line detection method for extraction of linear features from digital elevation data. In this method, raw elevation data is used for generating shaded relief images using the Lambertian reflection model, wherein the illumination direction is controlled by the user. The Directional Segment Detection Algorithm (DSDA) is used for detecting linear topographic features in user-defined trends. Locational information about these linear features is stored in the computer as coordinate pairs amenable to editing and subsequent analysis. Finally, three-dimensional terrain models are generated by combining the digital elevation data and satellite images. The experiments were carried out using digital elevation data of southwest Japan and Landsat MSS data.  相似文献   

Vegetation history after the late period of the Last Glacial Age based on phytolith records in Nangodani Valley basin,southern part of the Aso caldera,Japan     

Yasuo Miyabuchi  Shinji Sugiyama 《第四纪科学杂志》2020,35(1-2):304-315

Vegetation history after the late period of the Last Glacial Age has been reconstructed using phytolith records obtained from three tephra sections in the Nangodani Valley basin, southern part of the Aso caldera, south-west Japan. The topography of the Nangodani Valley basin is divided into three types: somma (caldera rim and wall), caldera floor (central valley) and post-caldera central cone slope. The vegetation transitions after the late period of the Last Glacial Age in the basin vary between these topographic types. The differences can be explained based on human activities in the valley basin. Grassland dominated by Sasa and Pleioblastus dwarf bamboos (before 8 ka) and Miscanthus and other Andropogoneae pampas grasses (after 8 ka) occurred in the central valley and on the post-caldera central cone slope, which were strongly affected by human activities including a long period of burning. In contrast, forest with an understory of Bambusoideae plants was preserved on the caldera rim and wall, which was inaccessible because of its steep topography, during the Holocene.  相似文献   

Particle-Image Velocimetry Measurements of Separation and Re-attachment of Airflow over Two-Dimensional Hills with Various Slope Angles and Approach-Flow Characteristics     

Isao Kanda  Yukio Yamao  Kiyoshi Uehara  Shinji Wakamatsu 《Boundary-Layer Meteorology》2013,148(1):157-175

Airflow over two-dimensional hills was investigated in a wind tunnel using particle image velocimetry. We focus on the flow separation behaviour. A trapezoidal hill shape was used in most of the experimental runs, but the critical slope angle for flow separation was approximately the same as that established for smooth hill shapes. The re-attachment point of the separated flow became farther from the hill as the slope angle $\theta $ increased, reaching a saturation of about seven times the hill height for $\theta \gtrsim 60^\circ $ . Increasing the upwind surface roughness length was found to suppress flow separation. This tendency is analogous to the previous experimental results for turbulent boundary layers on flat plates. The boundary-layer thickness varied by the presence or absence of Counihan-type spires and a castellated fence at the test-section entrance had negligible effect on the flow separation.  相似文献   

敦煌地区沙尘气溶胶质量浓度的观测研究   总被引：18，自引：6，他引：12  

刘立超  沈志宝  王涛  周茅先  矢吹貞代  金山晋司 《高原气象》2005,24(5):765-771

在沙尘源区进行长期监测是获取区域代表性沙尘气溶胶质量浓度特征的重要研究方法。敦煌位于甘肃省河西走廊的西端,是中国北方主要沙尘源区之一,利用大流量采样器和安德森采样器进行了长达30个月的试验观测研究,获得了该地区沙尘气溶胶的基本特征。其年变化特征与气象资料的年变化关系密切;针对典型天气过程的观测结果表明,不同天气条件（背景大气、浮尘、扬沙和沙尘暴）下TSP浓度存在倍数关系和量级的差异,其质量浓度随粒径的分布特征也明显不同;并与2001年9月-2004年3月在腾格里沙漠东南缘沙坡头地区的一些观测结果进行了比较分析。  相似文献   

Expected changes in future agro-climatological conditions in Northeast Thailand and their differences between general circulation models     

Yoshimitsu Masaki  Yasushi Ishigooka  Tsuneo Kuwagata  Shinkichi Goto  Shinji Sawano  Toshihiro Hasegawa 《Theoretical and Applied Climatology》2011,106(3-4):383-401

We have studied future changes in the atmospheric and hydrological environments in Northeast Thailand from the viewpoint of risk assessment of future cultural environments in crop fields. To obtain robust and reliable estimation for future climate, ten general circulation models under three warming scenarios, B1, A1B, and A2, were used in this study. The obtained change trends show that daily maximum air temperature and precipitation will increase by 2.6°C and 4.0%, respectively, whereas soil moisture will decrease by c.a. 1% point in volumetric water content at the end of this century under the A1B scenario. Seasonal contrasts in precipitation will intensify: precipitation increases in the rainy season and precipitation decreases in the dry season. Soil moisture will slightly decrease almost throughout the year. Despite a homogeneous increase in the air temperature over Northeast Thailand, a future decrease in soil water content will show a geographically inhomogeneous distribution: Soil will experience a relative larger decrease in wetness at a shallow depth on the Khorat plateau than in the surrounding mountainous area, reflecting vegetation cover and soil texture. The predicted increase in air temperature is relatively consistent between general circulation models. In contrast, relatively large intermodel differences in precipitation, especially in long-term trends, produce unwanted bias errors in the estimation of other hydrological elements, such as soil moisture and evaporation, and cause uncertainties in projection of the agro-climatological environment. Offline hydrological simulation with a wide precipitation range is one strategy to compensate for such uncertainties and to obtain reliable risk assessment of future cultural conditions in rainfed paddy fields in Northeast Thailand.  相似文献   

Mineralogy and geochemistry of shallow sediments of Sonargaon, Bangladesh and implications for arsenic dynamics: Focusing on the role of organic matter     

Ashraf Ali Seddique  Harue MasudaMuneki Mitamura  Keiji ShinodaToshiro Yamanaka  Shinji NakayaKazi Matin Ahmed 《Applied Geochemistry》2011,26(4):587-599

Mineralogy and geochemistry of modern shallow sediments (up to 5 m thick) within the zone of water table fluctuations were studied to determine the likely sources and processes responsible for releasing As into groundwater. Samples were collected from different geological settings with varying groundwater As concentrations during dry (December 2005) and wet (September 2006) seasons at Sonargaon, Bangladesh. Stratigraphic sequences of the studied sediments showed three distinct lithofacies, viz. clayey-silt, silty-clay, and silty-very fine sand, corresponding to fine-grained overbank associations. Total As concentrations of shallow sediments ranged from <1 to 16 mg/kg without a significant difference in the range of As concentrations between the seasons. Sequential chemical extraction analysis of As revealed that >80% of the As was fixed in insoluble and organic phases, while the amount of As in reducible and acid-soluble phases was very low (<20%) and varied inversely with total As content. Total As concentration varied with mica content (muscovite and biotite) and its related elements (Al, Mg and Fe), but not with total organic C, suggesting that biotite is the major host phase of As. Arsenic appears to be liberated from biotite and/or other As-bearing minerals via chemical weathering (i.e., hydration-decomposition), either from the near-surface sediments which are subject to seasonal cycling of the redox conditions, or from within the aquifer sediments. Once released, progressive diagenesis to form As-bearing organic matter may be responsible for controlling As distribution in the sediments and coexisting groundwater of the study area.  相似文献   

The period–luminosity relation for type II Cepheids in globular clusters     

Noriyuki Matsunaga  Hinako Fukushi  Yoshikazu Nakada  Toshihiko Tanabé  Michael W. Feast  John W. Menzies  Yoshifusa Ita  Shogo Nishiyama  Daisuke Baba  Takahiro Naoi  Hidehiko Nakaya  Takahiro Kawadu  Akika Ishihara  Daisuke Kato 《Monthly notices of the Royal Astronomical Society》2006,370(4):1979-1990

We report the result of our near-infrared observations ( JHK _s) for type II Cepheids (including possible RV Tau stars) in galactic globular clusters. We detected variations of 46 variables in 26 clusters (10 new discoveries in seven clusters) and present their light curves. Their periods range from 1.2 d to over 80 d. They show a well-defined period–luminosity relation at each wavelength. Two type II Cepheids in NGC 6441 also obey the relation if we assume the horizontal branch stars in NGC 6441 are as bright as those in metal-poor globular clusters in spite of the high metallicity of the cluster. This result supports the high luminosity which has been suggested for the RR Lyr variables in this cluster. The period–luminosity relation can be reproduced using the pulsation equation     assuming that all the stars have the same mass. Cluster RR Lyr variables were found to lie on an extrapolation of the period–luminosity relation. These results provide important constraints on the parameters of the variable stars.
Using Two Micron All-Sky Survey (2MASS) data, we show that the type II Cepheids in the Large Magellanic Cloud (LMC) fit our period–luminosity relation within the expected scatter at the shorter periods. However, at long periods (   P > 40  d, i.e. in the RV Tau star range) the LMC field variables are brighter by about one magnitude than those of similar periods in galactic globular clusters. The long-period cluster stars also differ from both these LMC stars and galactic field RV Tau stars in a colour–colour diagram. The reasons for these differences are discussed.  相似文献   

Near-infrared study of CIZA J1324.7-5736, the second richest cluster of galaxies in the Great Attractor     

T. Nagayama  P. A. Woudt  K. Wakamatsu  S. Nishiyama  C. Nagashima  D. Kato  T. Nagata  H. Nakaya  K. Sugitani  M. Tamura  S. Sato 《Monthly notices of the Royal Astronomical Society》2006,368(2):534-543

We present the result of a deep near-infrared survey of the newly identified X-ray luminous cluster of galaxies CIZA J1324.7-5736 in the Great Attractor (GA) region. In a 35 × 35 arcmin² region, 111 galaxy candidates with   r _{Ks 20} > arcsec  are identified. Comparison of the extinction-corrected   K _s   -band luminosity function of CIZA J1324.7-5736 with those of nearby clusters indicates that the richness class of CIZA J1324.7-5736 is almost the same as, or richer than, the Pavo, Centaurus and Hydra clusters but poorer than the Coma, Perseus and Norma clusters. CIZA J1324.7-5736 is possibly the second richest cluster in the GA region following the Norma cluster. The position of CIZA J1324.7-5736 [in the ( l , b , v ) space] is close to the Centaurus–Crux cluster and the agglomeration of galaxies detected by the Parkes H  i survey. CIZA J1324.7-5736, together with the Centaurus–Crux cluster and the H  i galaxy agglomeration, is most likely to be one of the richest local concentrations in the GA overdensity of galaxies.  相似文献