Layout design of rockbolts for natural ground reinforcement     

Junji Kato  Keiichiro Ishii  Kenjiro Terada  Takashi Kyoya 《国际地质力学数值与分析法杂志》2014,38(3):236-255

The present study addresses a layout design of rockbolts for reinforcing natural ground structures applying a special optimization method, called multiphase layout optimization. Rockbolts are used to tighten loosed natural ground, and the layout of rockbolts are determined without sufficient information about the physical properties of the ground materials. Because of this uncertainty, unexpected deformation often occurs at the excavation surface of natural ground. In that case, it is requested to determine an effective layout of the additional rockbolts promptly with respect to the actual deformation at the construction site. However, it is not easy to determine the optimal layout because of its complexity, and consequently, it has no choice but to determine the layout in an empirical way. This study introduces a numerical approach to determine an optimal layout of rockbolts with respect to arbitrarily possible deformation of natural ground. The objective is to maximize the stiffness of the overall ground structure reinforced with rockbolts. For optimization, a gradient‐based optimization scheme is applied because of its numerical efficiency. It was verified from a series of numerical examples that this method has great potential to improve the stiffness of the overall ground structure and shows a certain applicability to a practical design. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Review on observational studies of western tropical Pacific Ocean circulation and climate     

Hu  Dunxin  Wang  Fan  Sprintall  Janet  Wu  Lixin  Riser  Stephen  Cravatte  Sophie  Gordon  Arnold  Zhang  Linlin  Chen  Dake  Zhou  Hui  Ando  Kentaro  Wang  Jianing  Lee  Jae-Hak  Hu  Shijian  Wang  Jing  Zhang  Dongxiao  Feng  Junqiao  Liu  Lingling  Villanoy  Cesar  Kaluwin  Chalapan  Qu  Tangdong  Ma  Yixin 《中国海洋湖沼学报》2020,38(4):906-929

The Western Tropical Pacific(WTP) Ocean holds the largest area of warm water(28℃) in the world ocean referred to as the Western Pacific Warm Pool(WPWP),which modulates the regional and global climate through strong atmospheric convection and its variability.The WTP is unique in terms of its complex 3-D ocean circulation system and intensive multiscale variability,making it crucial in the water and energy cycle of the global ocean.Great advances have been made in understanding the complexity of the WTP ocean circulation and associated climate impact by the international scientific community since the 1960 s through field experiments.In this study,we review the evolving insight to the 3-D structure and multi-scale variability of the ocean circulation in the WTP and their climatic impacts based on in-situ ocean observations in the past decades,with emphasis on the achievements since 2000.The challenges and open que stions remaining are reviewed as well as future plan for international study of the WTP ocean circulation and climate.  相似文献   

Sound velocity and elastic properties of Fe–Ni and Fe–Ni–C liquids at high pressure     

Soma Kuwabara  Hidenori Terasaki  Keisuke Nishida  Yuta Shimoyama  Yusaku Takubo  Yuji Higo  Yuki Shibazaki  Satoru Urakawa  Kentaro Uesugi  Akihisa Takeuchi  Tadashi Kondo 《Physics and Chemistry of Minerals》2016,43(3):229-236

The sound velocity (V _P) of liquid Fe–10 wt% Ni and Fe–10 wt% Ni–4 wt% C up to 6.6 GPa was studied using the ultrasonic pulse-echo method combined with synchrotron X-ray techniques. The obtained V _P of liquid Fe–Ni is insensitive to temperature, whereas that of liquid Fe–Ni–C tends to decrease with increasing temperature. The V _P values of both liquid Fe–Ni and Fe–Ni–C increase with pressure. Alloying with 10 wt% of Ni slightly reduces the V _P of liquid Fe, whereas alloying with C is likely to increase the V _P. However, a difference in V _P between liquid Fe–Ni and Fe–Ni–C becomes to be smaller at higher temperature. By fitting the measured V _P data with the Murnaghan equation of state, the adiabatic bulk modulus (K _S0) and its pressure derivative (K _S ^′ ) were obtained to be K _S0 = 103 GPa and K _S ^′  = 5.7 for liquid Fe–Ni and K _S0 = 110 GPa and K _S ^′  = 7.6 for liquid Fe–Ni–C. The calculated density of liquid Fe–Ni–C using the obtained elastic parameters was consistent with the density values measured directly using the X-ray computed tomography technique. In the relation between the density (ρ) and sound velocity (V _P) at 5 GPa (the lunar core condition), it was found that the effect of alloying Fe with Ni was that ρ increased mildly and V _P decreased, whereas the effect of C dissolution was to decrease ρ but increase V _P. In contrast, alloying with S significantly reduces both ρ and V _P. Therefore, the effects of light elements (C and S) and Ni on the ρ and V _P of liquid Fe are quite different under the lunar core conditions, providing a clue to constrain the light element in the lunar core by comparing with lunar seismic data.  相似文献   

CFC Indicating Renewal of the Japan Sea Deep Water in Winter 2000–2001     

Shizuo Tsunogai  Kentaro Kawada  Shuichi Watanabe  Takafumi Aramaki 《Journal of Oceanography》2003,59(5):685-693

The distributions of CFC (chlorofluorocarbon) in the water column was determined twice in 2000 and 2001 in the northwestern Japan Sea. In 2000 the CFC-11 concentration decreased almost exponentially with depth from 6 pmol/kg at a few hundred m deep to 0.3 pmol/kg or less at the bottom of about 3400 m depth at three stations (40–41°N, 132–133°E) about 300 km off Vladivostok. In 2001 the CFC-11 concentration increased sharply up to 2 pmol/kg in the bottom water, while it did not increase at a station (42.0°N, 136.5°E) about 450 km away to the northeast. This is due to the renewal of the bottom water which is replaced by the surface water flowing down along the continental slope, as suggested by Tsunogai et al. (1999), who proposed the continental shelf pump. Furthermore, an increase in the CFC-11 concentration was observed throughout the entire water column above 3000 m depth, although the proportion of the increase was about 20%, which was one order of magnitude smaller than that in the bottom water. The increase in inventory is almost four times larger than that in the bottom water below 3000 m depth which is equivalent to about 1/6 of the total inventory found in 2000. The increase also means that 3% of the deep water was replaced by the recent surface water, or, if the turnover occurs every year, that the turnover time of the deep water to be about 30 years. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Highly alkaline,high-temperature hydrothermal fluids in the early Archean ocean     

Takazo Shibuya  Tsuyoshi Komiya  Kentaro Nakamura  Ken Takai  Shigenori Maruyama 《Precambrian Research》2010

Based on the petrology of hydrothermally altered Archean basaltic greenstones, thermodynamic calculations of phase equilibria were conducted to estimate the composition of a high-temperature (∼350 °C) hydrothermal fluid in an Archean subseafloor basalt-hosted hydrothermal system. The results indicate that the hydrothermal fluid was highly alkaline attributed to the presence of calcite in the alteration minerals under a high-CO₂ condition, and predict a generation of SiO₂-rich, Fe-poor hydrothermal fluids in the Archean subseafloor hydrothermal system. The chemically reactive mixing zones between alkaline hydrothermal fluids and slightly acidic-neutral seawater are characterized by inverse pH and chemical polarity to modern hydrothermal systems, leading to extensive precipitation of silica and iron oxyhydroxides on/under the seafloor. Such processes can be responsible for the abiotic formation of voluminous chert and subseafloor silica dike, the mechanism of silicification, and the pH-controlled generation of banded iron formation that has been arising mainly from the redox chemistry in the Archean ocean. Such high-temperature alkaline fluids could have had a significant role not only in the early ocean geochemical processes but also in the early evolution of life.  相似文献   

History of the Sole Source Aquifer Program: A Community-Based Approach for Protecting Aquifers Used for Drinking Water Supply     

William J. McCabe  Charles A. Job  John J. Simons  John S. Graves  Calvin J. Terada 《Ground Water Monitoring & Remediation》1997,17(3):78-86

The Sole Source Aquifer Program has helped prevent contamination of many community drinking water supplies. If an aquifer supplies the sole or principal source of a community's drinking water, a local ground water user may petition the Environmental Protection Agency (EPA) under the Safe Drinking Water Act for its designation and protection as a "sole source aquifer." Since 1974, residents and officials of 65 communities and multi-community areas have petitioned and received assistance from the EPA to prevent contamination of their local ground water source of drinking water. This designation means that EPA may review federal financially assisted projects to determine if they would contaminate the aquifer and cause a public health hazard. If they could cause contamination, EPA can request that the project be modified or stopped. The significance of this program in terms of population served and funds affected has been substantial, indicating the Sole Source Aquifer Program has been an important local tool for protecting ground water used as a source of drinking water. Information is given on three different examples of sole source aquifer designations protected under this program: the New Jersey Coastal Plain Aquifer System, the Great Miami River Buried Valley Aquifer System (Ohio), and the Eastern Snake River Plain Aquifer (Idaho), serving populations of 543,000, 921,000, and 275,000, respectively. In all three examples, preventing ground water contamination through the Sole Source Aquifer Program has protected the community drinking water supply.  相似文献   

Geochemical characteristics of zircons in the Ashizuri A‐type granitoids: An additional granite topology tool for detrital zircon studies          下载免费PDF全文

Yusuke Sawaki  Kazue Suzuki  Hisashi Asanuma  Satoki Okabayashi  Kentaro Hattori  Takuya Saito  Takafumi Hirata 《Island Arc》2017,26(6)

Zircon is resistant to alteration over a wide range of geological environments, and isotopic ratios within the mineral provide constraints on ages and their parental magmas. Trace element compositions in zircon are also expected to reflect those of their parent magmas, and have a potential as essential indicators for their host rocks. Because most detrital zircons that accumulate at river mouths are derived primarily from granitoids, the classification of zircon within granitoids is potentially meaningful. This study employs the conventional classification scheme of granites (I‐, S‐, M‐, and A‐types). To clarify geochemical characteristics of zircons in A‐type granites, trace element compositions of zircons extracted from the A‐type Ashizuri granitoids were examined. Zircons from the Ashizuri granitoids commonly show enrichments of heavy rare earth elements and positive Ce anomalies, indicating that these zircons were igneous in origin. In addition, zircons in these A‐type granites are characterized by enrichments of Nb, Y, Ta, Th, and U and strong negative Eu anomalies, which exhibit good positive correlations with those in their whole rocks. This fact indicates that these signatures in zircons reflect well those in their parental bodies and are useful in identifying zircons derived from A‐type granite. Based on compilations of available data, zircons from A‐type granites can be clearly discriminated from other‐types of granites within Nb/Sr–Eu anomaly, U/Sr–Eu anomaly, Nb/Sr–U/Sr, and Nb/Sr–Ta/Sr cross‐plots. All indices used in these diagrams were selected based on the geochemical features of both zircon and whole rock of A‐type granites. Application of these discrimination diagrams to detrital zircons will likely provide further insights. For example, some Hadean detrital zircons plot in similar fields to A‐type granites, implying the existence of A‐type magmatism in the Earth's earliest history.  相似文献   

Eocene extensional tectonics in the Amakusa region,northern Ryukyu arc     

Kentaro Ushimaru  Atsushi Yamaji 《Island Arc》2024,33(1):e12511

Paleogene surface tectonics in Japan is not well understood because of the paucity of onshore Paleogene stratigraphic records except for those from accretionary complexes. Paralic Paleogene formations remaining in SW Japan are usually so thin that it is difficult to decipher the tectonics from them. However, the Eocene paralic sedimentary package with a thickness of kilometers indicates syn-depositional tectonic subsidence by a few kilometers in the Amakusa archipelago, west of Kyushu Island. Thus, we made a detailed geological map of the Eocene formations in an area of ~50 square kilometers in the northwestern part of the archipelago. We identified NE-SW and NW-SE trending normal faults, most of which were recognized by previous researchers, and also discovered low-angle faults. NW-SE trending ones are known to be of the Miocene. NE-SW trending and low-angle normal faults are the oldest map-scale structures in the Eocene ones. It is not obvious within the above-mentioned area whether those normal faults are accompanied by growth strata. However, the significant southeastward thickening of the Eocene formations across the Amakusa archipelago suggests that they filled a large half graben with the basin margin fault along the eastern side of the archipelago. This basin model is consistent with the N-S to NW-SE transport directions of the low-angle and NE-SW trending normal faults. Since many NE-SW to EW trending Eocene grabens were formed in the offshore regions west of Kyushu Island and in the East China Sea, the Amakusa region was probably a northeastern branch of the rift system. The geologic structures and depositional ages of the Eocene formations indicate that the Eocene extensional tectonics removed the overlying strata to some extent for the high-P/T Takahama Metamorphic Rocks which crops out to the south of our study area.  相似文献   

X-ray beaming caused by resonance scattering in the accretion column of magnetic cataclysmic variables     

Y. Terada  M. Ishida  K. Makishima  T. Imanari  R. Fujimoto  K. Matsuzaki  H. Kaneda 《Monthly notices of the Royal Astronomical Society》2001,328(1):112-126

Extremely strong ionized Fe emission lines, with equivalent widths reaching ∼4000 eV, were discovered by ASCA from a few Galactic compact objects, including AX J2315−0592, RX J1802.1+1804 and AX J1842.8−0423. These objects are thought to be binary systems containing magnetized white dwarfs (WDs). A possible interpretation of the strong Fe K line is the line-photon collimation in the WD accretion column, as a result of resonance scattering of line photons. The collimation occurs when the accretion column has a flat shape, and the effect is augmented by the vertical velocity gradient, which reduces the resonant trapping of resonant photons along the magnetic field lines. This effect was quantitatively confirmed with Monte Carlo simulations. Furthermore, with ASCA observations of the polar V834 Centauri, this collimation effect was clearly detected as a rotational modulation of the equivalent width of the Fe K emission line. The extremely strong emission lines mentioned above can be explained consistently by our interpretation. Combining this effect with other X-ray information, the geometry and plasma parameters in the accretion column were determined.  相似文献   

Discovery of a New Pulsating X-Ray Source with a 1549.1 Second Period, AX J183220-0840     

Sugizaki M  Kinugasa K  Matsuzaki K  Terada Y  Yamauchi S  Yokogawa J 《The Astrophysical journal》2000,534(2):L181-L184

A new pulsating X-ray source, AX J183220-0840, with a 1549.1 s period was discovered at R.A.=18h32m20s and decl.=-8&j0;40'30" (J2000, with an uncertainty of 0&farcm;6) during an ASCA observation on the Galactic plane. The source was observed two times, in 1997 and in 1999. A phase-averaged X-ray flux of 1.1x10-11 ergs cm-2 s-1 and a pulsation period of 1549.1+/-0.4 s were consistently obtained from these two observations. The X-ray spectrum was represented by a flat, absorbed power law with a photon index of Gamma approximately 0.8 and an absorption column density of NH approximately 1.3x1022 cm-2. Also, a signature of iron K-shell line emission with a centroid of 6.7 keV and an equivalent width of approximately 450 eV was detected. From the pulsation period and the iron-line feature, AX J183220-0840 is likely to be a magnetic white dwarf binary with a complexly absorbed thermal spectrum with a temperature of about 10 keV.  相似文献