Development of partial factor design method on bearing capacity of pile foundations for Japanese Specifications for Highway Bridges     

Toshiaki Nanazawa  Tetsuya Kouno  Gaku Sakashita  Kazunori Oshiro 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2019,13(3):166-175

ABSTRACT

This paper shows the development of a partial factor design method on the bearing capacity of pile foundations for Japanese Specifications for Highway Bridges. Firstly, estimation design equations on the bearing capacities of pile foundations are improved by analysis of pile load test results and uncertainties in the bearing capacities are evaluated. Secondly, the reliabilities of pile foundations designed by the former specifications are evaluated based on reliability analysis considering the uncertainties in the bearing capacities and coefficients of subgrade reaction. Finally, a partial factor design method is developed based on the target reliability index obtained based on the conventional pile installation method by the pile installation methods. The factors are different for each pile installation method.  相似文献   

Infrared photometry of Venus: Variation during 10 years?     

Tetsuya Nagata  Shuji Sato  Tadashi Mukai  Sonoyo Mukai 《Icarus》1985,63(2):217-221

The infrared flux of Venus has been observed with a narrowband filter (λ = 3.6 μm, Δλ = 0.08 μm) from 1982 through 1984, covering a range of the phase angle α from 27 to 94°. Normalized values of flux at the Venus-Earth distance of 1 AU were (4.0–5.4) × 10^?17W/cm²/cm^?1 and the α dependence of the data is rather weak. Furthermore, when the evening terminator of Venus was seen, lower values of flux were obtained in contrast with higher values at the morning terminator. The α dependence is quite different from that of J.V. Martonchik and R. Beer (1975, J. Atmos. Sci.32, 1151–1156). Since we cannot find any significant problem in the two observational methods, the difference might suggest an intrinsic time variation of haze particles during these 10 years in the upper haze layer of the Venus cloud.  相似文献   

Enrichment Ratio-Tonnage Diagrams for Resource Assessment     

Shoji  Tetsuya 《Natural Resources Research》2002,11(4):273-287

The enrichment ratio (ER), defined as the ratio of grade of a metal element in a deposit to the crustal abundance of the metal, is proposed for assessing mineral resources. According to the definition, the enrichment ratio of a polymetallic deposit is given as a sum of enrichment ratios of all metals. The relation between ER and the cumulative tonnage integrated from the high ER side of about 4750 deposits in the world is approximated by the combination of three exponential functions crossing at ER values of 16 · 10³ and 600. High ER deposits are expected for the commodities Ag, Pb, and Au+Ag, and for epithermal, mesothermal, unconformity-related and vein types. In contrast, low ER deposits are typical for the commodities Cu, Mn, Mo, Ni, and U, and for chemically precipitated, Cyprus, laterite, orthomagmatic, pegmatite, placer, porphyry, and sandstone deposits. The critical ER value of the low ER class (the differential metal amount decreases with decreasing ER in the regions lower than the value) is 250 in all deposits, 610 in W+Mo, 2800 in Pb+Zn and 360 in Au+Ag, 530 in massive sulfides, 160 in the orthomagmatic type, 170 in placers, 220 in the porphyry type, 1900 in the replacement type, 580 in the stratabound type, 3400 in the unconformity-related type, and 1700 in vein type deposits. The frequency proportion determined by a keyword and a commodity provides valuable suggestions for mineral exploration: for example, the exploration target for chromite is a deposit characterized as orthomagmatic, whereas the expected commodity of a newly developed orthomagmatic deposit is chromite.  相似文献   

Precise determination of ferrous iron in silicate rocks     

Tetsuya YokoyamaEizo Nakamura 《Geochimica et cosmochimica acta》2002,66(6):1085-1093

We have developed a highly precise method for the determination of ferrous iron (Fe²⁺) in silicate rocks. Our new method is based on Wilson’s procedure (1955) in which surplus V⁵⁺ is used to oxidize Fe²⁺ into Fe³⁺ while equivalently reducing V⁵⁺ into V⁴⁺. Because V⁴⁺ is more resistant to atmospheric oxidation than Fe²⁺, Fe²⁺ in the sample can be determined by measuring unreacted V⁵⁺ by adding excess Fe²⁺ after sample decomposition and then titrating the unreacted Fe²⁺ with Cr⁶⁺. With our method, which involves conditioning the sample solution with 5 M H₂SO₄ in a relatively small beaker (7 mL), the oxidation of Fe²⁺ or V⁴⁺ that leads to erroneous results can be completely avoided, even in 100-h sample decompositions at 100°C. We have measured the concentration of FeO in 15 standard silicate rock powders provided by the Geological Survey of Japan (GSJ). Analytical reproducibility was better than 0.5% (1σ) for all but those samples that had small amounts of Fe²⁺ (<1.5 wt.% of FeO). Fourteen of these samples gave FeO contents significantly higher than the GSJ reference values. This likely indicates that the GSJ reference values, obtained by compiling previously published data, contain a large number of poor-quality data obtained by methods with lower recovery of Fe²⁺ caused by oxidation or insufficient sample decomposition during analyses. To achieve accurate determinations of Fe²⁺ in our method, several factors besides the oxidation must be considered, including: (1) long-term variations in the concentration of Fe²⁺ solution must be corrected; (2) excess use of the indicator must be avoided; and (3) the formation of inert FeF⁺ complex must be avoided during titration when using boric acid as a masking agent.  相似文献   

Surface lowering rates of uplifted limestone terraces estimated from the height of pedestals on a subtropical island of Japan     

Yukinori Matsukura  Akira Maekado  Hisashi Aoki  Tetsuya Kogure  Yoshihiko Kitano 《地球表面变化过程与地形》2007,32(7):1110-1115

In Kikai‐jima, south‐western Japan, many pedestal rocks have developed on the surface of Holocene raised coral‐reef terraces with known dates of emergence. Pedestals are formed just under boulders, which are considered to have been transported by tsunami and settled on a reef flat before emergence. On the assumption that boulders protect the underlying limestone terrace from rainfall solution, the rate of surface lowering of these limestone terraces was evaluated from the height of pedestals and the period of their formation. The result showed that the mean lowering rate over 6000 years is 205 mm/ky. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Preferential dissolution of SiO<Subscript>2</Subscript> from enstatite to H<Subscript>2</Subscript> fluid under high pressure and temperature     

Ayako Shinozaki  Hiroyuki Kagi  Hisako Hirai  Hiroaki Ohfuji  Taku Okada  Satoshi Nakano  Takehiko Yagi 《Physics and Chemistry of Minerals》2016,43(4):277-285

Stability and phase relations of coexisting enstatite and H₂ fluid were investigated in the pressure and temperature regions of 3.1–13.9 GPa and 1500–2000 K using laser-heated diamond-anvil cells. XRD measurements showed decomposition of enstatite upon heating to form forsterite, periclase, and coesite/stishovite. In the recovered samples, SiO₂ grains were found at the margin of the heating hot spot, suggesting that the SiO₂ component dissolved in the H₂ fluid during heating, then precipitated when its solubility decreased with decreasing temperature. Raman and infrared spectra of the coexisting fluid phase revealed that SiH₄ and H₂O molecules formed through the reaction between dissolved SiO₂ and H₂. In contrast, forsterite and periclase crystals were found within the hot spot, which were assumed to have replaced the initial orthoenstatite crystals without dissolution. Preferential dissolution of SiO₂ components of enstatite in H₂ fluid, as well as that observed in the forsterite H₂ system and the quartz H₂ system, implies that H₂-rich fluid enhances Mg/Si fractionation between the fluid and solid phases of mantle minerals.  相似文献   

Large-Eddy-Simulation Study of the Effects of Building-Height Variability on Turbulent Flows over an Actual Urban Area     

Toshiya Yoshida  Tetsuya Takemi  Mitsuaki Horiguchi 《Boundary-Layer Meteorology》2018,168(1):127-153

Large-eddy simulation (LES) is used to investigate the effects of building-height variability on turbulent flows over an actual urban area, the city of Kyoto, which is reproduced using a 2-m resolution digital surface dataset. Comparison of the morphological characteristics of Kyoto with those of European, North American, and other Japanese cities indicates a similarity to European cities but with more variable building heights. The performance of the LES model is validated and found to be consistent with turbulence observations obtained from a meteorological tower and from Doppler lidar. We conducted the following two numerical experiments: a control experiment using Kyoto buildings, and a sensitivity experiment in which all the building heights are set to the average height over the computational region \(h_{all}\). The difference of Reynolds stress at height \(z=2.5h_{all}\) between the control and sensitivity experiments is found to increase with the increase in the plan-area index (\(\lambda _p\)) for \(\lambda _p > 0.32\). Thus, values of \(\lambda _p\approx 0.3\) can be regarded as a threshold for distinguishing the effects of building-height variability. The quadrant analysis reveals that sweeps contribute to the increase in the Reynolds stress in the control experiment at a height \(z= 2.5h_{all}\). The exuberance in the control experiment at height \(z=0.5h_{all}\) is found to decrease with increase in the building-height variability. Although the extreme momentum flux at height \(z=2.5h_{all}\) in the control experiment appears around buildings, it contributes little to the total Reynolds stress and is not associated with coherent motions.  相似文献   

Nutrient dynamics in core sediments of an artificial basal medium prepared with steelmaking slag and dredged materials     

Ayumi Tsukasaki  Nobuo Tsurushima  Tetsuya Nakazato  Yu Huang  Terumi Tanimoto  Masahiro Suzumura  Wataru Nishijima 《Journal of Oceanography》2016,72(6):867-881

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Small-Amplitude Disturbances in a Radiating and ScatteringGrey MediumI. Solutions of Given Real Frequency ω     

Noboru Kaneko  Kazuhiko Morita  Tetsuya Satoh  Kiyotaka Toyama  Masaki Nishimura  Makoto Maekawa 《Astrophysics and Space Science》2000,274(3):601-641

We reanalyze the propagation of one-dimensional small-amplitude disturbances of given real frequency ω in a radiating and scattering grey medium using the Eddington approximation, which has been studied previously by us (Kaneko et al., 1976). Numerical results reveals three frequency regimes to be distinguished, and two wave modes always appear in each frequency regime. The governing equations and analytic solutions are derived for all wave modes using Whitham's method modified into quadratic form and approximate methods based on radiation thermodynamics. In the high-frequency regime appear the radiation-wave and adiabatic sound modes, which are damped by opacity and radiative cooling, respectively. Wave patterns in the intermediate-frequency and low-frequency regimes depend critically on the importance of radiation, for which the criterion is given in terms of the ratio of total specific heats at constant pressure and constant volume. When the radition overwhelms the matter (radiation-dominated case), the radiative mode in the intermediate-frequency regime is the constant-volume diffusion mode. When the matter overwhelms the radiation (matter-dominated case), damped radiation-wave and damped radiation-diffusion modes newly appear between the radiation-wave and constant-volume diffusion modes. The acoustic mode in the intermediate-frequency regime is the isothermal sound mode,which is damped by radiative cooling at higher frequencies and by radiation-thermal drag force at lower frequencies. Two modes appearing in the low-frequency regime are the isentropic radiation-acoustic and constant-pressure diffusion modes. The absorption coefficient derived for the former is shown to be a radiation-thermodynamic extension of that of Landau and Lifshitz (1987). The transition frequencies between all adjacent two modes are also derived to discuss the implications of them. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Sediment transport in high‐speed flows over a fixed bed: 1. Particle dynamics          下载免费PDF全文

Christian Auel  Ismail Albayrak  Tetsuya Sumi  Robert M. Boes 《地球表面变化过程与地形》2017,42(9):1365-1383

Particle dynamics are investigated experimentally in supercritical high‐speed open channel flow over a fixed planar bed of low relative roughness height simulating flows in high‐gradient non‐alluvial mountain streams and hydraulic structures. Non‐dimensional equations were developed for transport mode, particle velocity, hop length and hop height accounting for a wide range of literature data encompassing sub‐ and supercritical flow conditions as well as planar and alluvial bed configurations. Particles were dominantly transported in saltation and particle trajectories on planar beds were rather flat and long compared with alluvial bed data due to (1) increased lift forces by spinning motion, (2) strongly downward directed secondary currents, and (3) a planar flume bed where variation in particle reflection and damping effects were minor. The analysis of particle saltation trajectories revealed that the rising and falling limbs were almost symmetrical contradicting alluvial bed data. Furthermore, no or negligible effect of particle size and shape on particle dynamics were found. Implications of experimental findings for mechanistic saltation‐abrasion models are briefly discussed. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献