Railway embankment failure due to ballast layer breach caused by inundation flows     

Ryota Tsubaki  Yoshihisa Kawahara  Yasuhiro Ueda 《Natural Hazards》2017,87(2):717-738

A railway embankment constructed on a floodplain is at risk of damage due to flooding flows. The process and critical conditions that lead to railway embankment damage during flooding are not clearly understood, rendering risk estimations impossible and hindering the development of flood-resilient rail systems. For this work, we first reviewed records of railway damage in flood plains and flows through the ballast layer. The breaching process was selected as the focus of our study. We secondly specified the fundamental characteristics of flows through a ballast layer. The critical flow rate per unit width and the minimum upstream water depth required for initiating extensive ballast breaching were experimentally evaluated using a full-scale ballast layer with rails and sleepers constructed using materials originally utilized in actual railways. A two-dimensional flow model was then employed for estimating the flow through a ballast layer that was placed on an impermeable base embankment. A simple ballast breaching model was also employed in order to explore a higher flow rate condition that could not be represented in our experiment due to limited facilities. The breaching pattern represented by the simulation model corresponded to the breaching pattern observed in the experiment. In addition to the above, here, we also discuss the ballast breaching process based on qualitative field records and quantitative experimental results, as well as the ballast breaching process as represented by the simulation.  相似文献   

泥石流的二维数学模型   总被引：5，自引：2，他引：3  

王纯祥  白世伟  江崎哲郎  三谷泰浩 《岩土力学》2007,28(6):1237-1241

泥石流是在重力作用下,由砂粒石块和水等组成的固液混合物,是一种发生于山区的复杂的地质灾害现象。泥石流主要是由暴雨诱发引起的,它沿着复杂的三维地形高速流动,具有流体流动的特性。为了模拟泥石流的运动规律,预测降雨诱发的泥石流的到达距离和泛滥范围,减少和避免泥石流引起的灾害,把泥石和雨水组成的固液混合物假定为遵循均匀、连续、不可压缩的、非定常的牛顿流体运动规律。基于质量守恒方程和Naiver-stokes方程,采用深度积分方法,推导出了一个模拟泥石流运动的二维数学模型。所有方程式可用有限差分法来求解。结合GIS,该模型可用于预测泥石流的流动距离和泛滥范围,以及泛滥范围内的危险房屋和路段,也可以用于泥石流灾害的风险性分析。  相似文献   

Livestock wastes as a source of estrogens and their effects on wildlife of Manko tidal flat,Okinawa   总被引：9，自引：0，他引：9  

Tashiro Y  Takemura A  Fujii H  Takahira K  Nakanishi Y 《Marine pollution bulletin》2003,47(1-6):143-147

The Manko tidal flat in the southern part of Okinawa Island is an important visiting and wintering area for migratory birds and was added to the Ramsar Convention Register of Wetlands in 1999. This area used to be an inlet extending to the inner part of Naha Port, but recent reclamation projects have restricted its connection to the East China Sea. As is typical in rural regions of subtropical islands, the inhabitants in the Manko basin raise livestock, especially pigs, without employing sufficient waste treatment methods. As sewage treatment works are considered to be one of the main sources of environmental estrogens in urban areas, the significance of livestock farming as a source of estrogens in rural area is examined in this study. In the present study, total estrogenic activities in water and sediment samples from the Manko tidal flat and its basin were measured using a recombinant yeast screen method. Estrogenic activities (equivalent to 17beta-estradiol, E2) were around 10 ng l(-1) in water samples and more than 10 microg kg(-1) in some sediment samples. In addition, the concentrations of estrone (E1) and E2 in water samples measured using LC/MS/MS indicated a high contribution of environmental estrogens from livestock wastes.  相似文献   

Radiolarian Age of Red Chert from the Kunimiyama Ferromanganese Deposit in the Northern Chichibu Belt, Central Shikoku, Japan     

Koichiro Fujinaga  Yasuhiro Kato 《Resource Geology》2005,55(4):353-356

Abstract. The radiolarian age of red chert from the Kunimiyama area of the Northern Chichibu Belt was determined in order to constrain the depositional age of the Kunimiyama deposit that is among the largest ferromanganese deposits in Japan. Pseudoalbaillella cf scalprata Holdsworth and Jones, Pseudoalbaillella cf longicornis Ishiga and Imoto and Pseudoalbaillella sp. belonging to the Ps. lomentaria Zone are found in the red chert, indicating an age of middle Early Permian (middle Wolfcampian). The red chert occurs immediately above the ferromanganese deposit, and the boundary between them is gradual. Based on their mode of occurrence and geochemical features, it is most likely that radiolarian chert and ferromanganese precipitate accumulated simultaneously to produce red chert during the waning stage of submarine hydrothermal activity that was responsible for the Kunimiyama deposit. Consequently, the age of Kunimiyama stratiform ferromanganese deposit is constrained as middle Early Permian (middle Wolfcampian).  相似文献   

Radiolarian Age of Manganese Ore and Red Chert from the Ananai Stratiform Manganese Deposit in the Northern Chichibu Belt, Central Shikoku, Japan     

Kiyoko Kuwahara    Koichiro Fujinaga  Yasuhiro Kato 《Resource Geology》2006,56(4):415-421

Abstract. We obtain radiolarian fossils such as Follicucullus monacanthus, Pseudoalbaillella aff. globosa, Pseudoalbaillella cf fusiformis , and Pseudoalbaillella spp. belonging to the Pseudoalbaillella globosa and Follicucullus monacanthus Zones from manganese ore and associated red chert of the Ananai stratiform manganese deposit in the Northern Chichibu Belt, central Shikoku. The depositional age of the Ananai ore deposit is constrained as Guadalupian (Middle Permian) that is between 270.6 and 260.4 Ma in the updated geologic time scale.  相似文献   

Using VLBI fringe-phase information from geodetic experiments for short-period ionospheric studies     

Thomas Hobiger  Tetsuro Kondo  Yasuhiro Koyama  Kazuhiro Takashima  Harald Schuh 《Journal of Geodesy》2007,81(6-8):389-401

The usage of Very Long Baseline Interferometry (VLBI) fringe-phase information in geodetic VLBI is a new field of research, which can be used for the detection of short-period (i.e., several minutes) variations (scintillations) of the ionosphere. This paper presents a method for the extraction of such disturbances and discusses how dispersive influences can be separated from intra-scan delay variations. A proper functional and stochastic model for the separation of the different effects is presented and the algorithms are applied to real measurements. In an example, it is shown that a traveling ionospheric disturbance in Antarctica can be detected very precisely. A possible physical origin and the propagation properties of the disturbance are presented and the results are compared with GPS measurements. The benefit of this method for other applications is also discussed.  相似文献   

Influence of contamination on banded iron formations in the Isua supracrustal belt,West Greenland: Reevaluation of the Eoarchean seawater compositions     

Shogo Aoki  Chiho Kabashima  Yasuhiro Kato  Takafumi Hirata  Tsuyoshi Komiya 《地学前缘(英文版)》2018,9(4):1049-1072

Banded Iron Formations(BIFs) are chemical sediments, ubiquitously distributed in the Precambrian supracrustal belts; thus their trace element compositions are helpful for deciphering geochemical evolution on the Earth through time. However, it is necessary to elucidate factors controlling the whole-rock compositions in order to decode the ancient seawater compositions because their compositions are highly variable. We analyzed major and trace element contents of the BIFs in the 3.8-3.7 Ga Isua supracrustal belt(ISB), southern West Greenland. The BIFs are petrographically classified into four types:Black-,Gray-, Green-and White-types, respectively. The Green-type BIFs contain more amphiboles, and are significantly enriched in Co, Ni, Cu, Zn, Y, heavy rare earth element(HREE) and U contents. However,their bulk compositions are not suitable for estimate of seawater composition because the enrichment was caused by secondary mobility of metamorphic Mg, Ca and Si-rich fluid, involvement of carbonate minerals and silicate minerals of olivine and pyroxene and/or later silicification or contamination of volcanic and clastic materials. The White-type BIFs are predominant in quartz, and have lower transition element and REE contents. The Gray-type BIFs contain both quartz and magnetite. The Black-type BIFs are dominated by magnetite, and contain moderate to high transition element and REE contents. But,positive correlations of V, Ni, Zn and U contents with Zr contents suggest that involvement of detrital,volcanic and exhalative materials influences on their contents. The evidence for significant influence of the materials on the transition element contents such as Ni in the BIFs indicates the transition element contents in the Archean ocean were much lower than previously estimated. We reconstructed secular variations of V,Co, Zn and U contents of BIFs through time, which show Ni and Co contents decreased whereas V, Zn and U contents increased through time. Especially, the Ni and Co contents drastically decreased in the Mesoarchean rather than around the Great Oxidation Event. On the other hand, the V,Zn and U contents progressively increased from the Mesoarchean to the Proterozoic. Stratigraphical trends of the BIFs show increase in Y/Ho ratios and decrease in positive Eu anomaly upwards, respectively. The stratigraphic changes indicate that a ratio of hydrothermal fluid to seawater component gradually decrease through the deposition, and support the Eoarchean plate tectonics, analogous to the their stratigraphic variations of seafloor metalliferous sediments at present and in the Mesoarchean.  相似文献   

Diel behavior of stable isotopes of dissolved oxygen and dissolved inorganic carbon in rivers over a range of trophic conditions,and in a mesocosm experiment     

Stephen R. Parker  Christopher H. Gammons  Simon R. Poulson  Michael D. DeGrandpre  Charmaine L. Weyer  M. Garrett Smith  John N. Babcock  Yasuhiro Oba 《Chemical Geology》2010,269(1-2):22-32

Rates of diel (24-h) biogeochemical processes in rivers and their effect on daily changes in the concentration of metals and metalloids have been well documented in the literature over the last 20 years. Investigations into the effects of these processes on aquatic systems and the underlying mechanisms that control the processes can significantly improve our understanding of how natural aquatic environments function and will respond to changing environmental conditions and anthropogenic impacts. Daily changes in the rates of biogeochemical processes have, more recently, been shown to influence the stable isotope composition of dissolved oxygen and dissolved inorganic carbon in natural waters. Here we present a comprehensive picture of the persistence and reproducibility of diel cycles of the ¹⁸O composition of dissolved molecular oxygen (δ¹⁸O-DO) and the ¹³C composition of dissolved inorganic carbon (δ¹³C-DIC) across five Montana, USA rivers investigated over a 4-year period. A mesocosm experiment showed the same behavior in δ¹⁸O-DO and δ¹³C-DIC as seen in riverine settings across light and dark periods.A cross plot of δ¹⁸O-DO and δ¹³C-DIC from each stream exhibits a clockwise elliptical pattern which is attributed to the daily changes in the balance of metabolic rates as well as air–water gas exchange. The amplitude of the change in the isotope composition is shown to be directly related to the trophic state of the river and a relationship between net productivity and diel changes in δ¹⁸O-DO and δ¹³C-DIC is presented. This relationship between trophic status with δ¹⁸O-DO, δ¹³C-DIC and production emphasizes the significance of how rates of biogeochemical processes in natural systems can influence the daily changes in the composition of surface waters.  相似文献   

Rare Earth Elements as an Indicator to Origins of Skarn Deposits: Examples of the Kamioka Zn-Pb and Yoshiwara-Sannotake Cu(–Fe) Deposits in Japan     

Yasuhiro Kato 《Resource Geology》1999,49(4):183-198

Abstract: Systematic data of rare earth elements (REEs) are presented in order to put some constraints on the origin of hydrothermal fluids responsible for two contrastive skarn deposits in Japan; the Kamioka Zn-Pb and Yoshiwara-Sannotake Cu(-Fe) deposits. Carbon and oxygen isotopic studies have demonstrated that the hydrothermal fluids responsible for the Kamioka Zn-Pb deposits are of meteoric water origin whereas those for the Yoshiwara-Sannotake Cu(-Fe) deposits are of magmatic water origin. The REE abundances of epidote skarn derived from aluminous rocks, garnet and clinopyroxene in calcic exoskarn derived from limestone, and interstitial calcite associated with sulfide minerals were determined for these contrastive skarn deposits by inductively-coupled plasma mass spectrometry (ICP-MS). A significant difference in the REE concentrations is not found between epidote skarn and aluminous original rock (plagioclase-clinopyroxene rock, called Inishi rock) from the Kamioka Zn-Pb deposits, indicating that the REEs are generally immobile during the formation of epidote skarn, and that the REE concentrations of the hydrothermal fluid are considerably low relative to the aluminous original rock. In contrast, the epidote skarn exhibits enrichment of Eu with increasing total REE concentrations relative to the aluminous original rock (quartz diorite) in the Yoshiwara-Sannotake Cu(-Fe) deposits, implying a contribution of magmatic fluid derived from granitoids during the skarn formation. Limestone generally has much lower REE concentrations related to surrounding aluminous rocks, and thus the REE concentrations of garnet and clinopyroxene in calcic exoskarn, originated from limestone, are variable due to the interaction with the hydrothermal fluids. The chondrite-normalized REE patterns of garnet, clinopyroxene, and interstitial calcite exactly provide useful information on origins of hydrothermal fluids. The REE patterns of these minerals from the Kamioka Zn-Pb deposits show lower (Pr/Yb)cn ratios, and negative Ce and Eu anomalies inherited from limestone with the decrease of This suggests that the hydrothermal fluids responsible for the Kamioka Zn-Pb deposits were depleted in REEs, and were not magmatic water in origin, but presumably meteoric one. In striking contrast, the REE patterns of exoskarn minerals and calcite from the Yoshiwara-Sannotake Cu(-Fe) deposits exhibit a positive Eu anomaly, and high (Pr/Yb)cn ratios with the considerable increase of σREE and the disappearance of negative Ce anomaly, implying that the fluids were dominantly of magmatic origin. The REE indices are very likely to be an excellent indicator to origins of the skarn deposits.  相似文献   

A GPU based real-time GPS software receiver     

Thomas Hobiger  Tadahiro Gotoh  Jun Amagai  Yasuhiro Koyama  Tetsuro Kondo 《GPS Solutions》2010,14(2):207-216

Off-the-shelf graphics processing units provide low-cost massive parallel computing performance, which can be utilized for the implementation of a GPS software receiver. In order to realize a real-time capable system the crucial stages of the receiver should be optimized to suit the requirements of a parallel processor. Moreover, the receiver should be capable to provide wider correlation functions and provide easy access to the spectral domain of the signals. Thus, the most suitable correlation algorithm, which forms the core part of each receivers should be chosen and implemented on the graphics processor. Since the sampling rate of the received signal limits the real-time capabilities of the software radio it is necessary to determine an optimum value, considering that the precision of the observable varies with sampling bandwidth. We are going to discuss details and present our single frequency multi-channel implementation, which is capable of operating in real-time mode. Our implementation differs from other solutions by the wideness of the correlation function and allows simple handling of data in the spectral domain. Comparison with output from a commercial hardware receiver, which shares the antenna with the software radio, confirms the consistency and accuracy of our development.  相似文献