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1.
Application of Convergence Confinement Analysis to the study of preceding displacement of a squeezing rock tunnel 总被引：4，自引：0，他引：4
T. Kitagawa T. Kumeta T. Ichizyo S. Soga M. Sato M. Yasukawa 《Rock Mechanics and Rock Engineering》1991,24(1):31-51
Summary This paper deals with a study on the geomechanical behavior of the rock mass around the tunnel. The Convergence Confinement Analysis is one of the most appropriate way to estimate this behavior. Elasto-plastic models proposed by Hoek and Brown, Egger and Kastner were adopted in this study.Measurements of the preceding displacement were performed in a road tunnel in Japan, the geology of which is Neogene squeezing mudstone. The measured data was compared with the results of Convergence Confinement Analysis.The preceding displacement was about 40% against the upper bench face converged displacement and 17% against the final converged displacement. Meanwhile, it increased drastically in lower bench excavation step.Back analysis was also executed to calculate the extension of the plastic zone of the rock mass, which was half of that estimated by Convergence Confinement Analysis in upper bench excavation step. But, in lower bench excavation step, the results of the two analyses were very similar. The support pressure and support stiffness were also calculated. 相似文献
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Kazutaka Yamaoka Yoshihiro Ueda Hajime Inoue Fumiaki Nagase Ken Ebisawa Taro Kotani Yasuo Tanaka 《Astrophysics and Space Science》2001,276(1):19-22
We summarize the ASCA observations of the two Galactic superluminal sources GRO J1655–40 and GRS 1915+105, focusing on theabsorption line features.The high spectroscopic capability of ASCA enabled us to detectiron-K absorption line features from both objects. This is direct evidence for the presence of highly ionized plasma in a non-spherical configuration around a black hole, and is considered to be a unique signature of superluminal jet systems. The candidate of the line-absorber would be a part of an accretion disk at a distance of 109-11 cm from the central X-ray source. 相似文献
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This paper presents an experimental study on the performance of a shear-sliding stud-type damper composed of multiple friction units with high-tension bolts and disc springs. A numerical evaluation of the response reduction effects achieved by the stud-type damper is also presented. In dynamic loading tests, the behavior of stud-type multiunit friction damper specimens was investigated. Three different full-scale damper specimens, which were composed of five, six, or seven friction units with two or four sliding surfaces, were incorporated into loading devices for testing. The stud-type friction dampers demonstrated stable rigid-plastic hysteresis loops without any remarkable decrease in the sliding force even when subjected to repetitive loading, in addition to showing no unstable behavior such as lateral buckling. The damper produced a total sliding force approximately proportional to the number of sliding surfaces and friction units. The total sliding force of the stud-type damper can thus be estimated by summing the contributions of each friction unit. In an earthquake response simulation, the control effects achieved by stud-type dampers incorporated into an analytical high-rise building model under various input waves, including long-period, long-duration and pulse-like ground motions, were evaluated. A satisfactory response reduction was obtained by installing the developed stud-type dampers into the main frame without negatively impacting usability and convenience in terms of building planning. 相似文献
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Takenobu Toyota Shinya Takatsuji Kazutaka Tateyama Kazuhiro Naoki Kay I. Ohshima 《Journal of Oceanography》2007,63(3):393-411
The general properties of sea ice and overlying snow in the southern Sea of Okhotsk were examined during early February of
2003 to 2005 with the P/V “Soya”. Thin section analysis of crystal structure revealed that frazil ice (48% of total core length)
was more prevalent than columnar ice (39%) and that stratigraphic layering was prominent with a mean layer thickness of 12
cm, indicating that dynamic processes are essential to ice growth. The mean thickness of ice blocks and visual observations
suggest that ridging dominates the deformation process above thicknesses of 30 to 40 cm. As for snow, it was found that faceted
crystals and depth hoar are dominant (78%), as which is also common in the Antarctic sea ice, and is indicative of the strong
vertical temperature gradients within the snow. Stable isotope measurements (δ18O) indicate that snow ice occupies 9% of total core length and that the mass fraction of meteoric ice accounts for 1 to 2%
of total ice volume, which is lower than the Antarctic sea ice. Associated with this, the effective fractionation coefficient
during the freezing of seawater was also derived. Snow ice was characterized by lower density, higher salinity, and nearly
twice the gas content of ice of seawater origin. In addition, it is shown that the surface brine volume fraction and freeboard
are well correlated with ice thickness, indicating some promise for remote sensing approaches to the estimation of ice thickness. 相似文献
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Tetsuya Nishikawa Yutaka Hori Satoshi Nagai Kazutaka Miyahara Yukinobu Nakamura Kazuhiro Harada Minoru Tanda Takehiko Manabe Kuninao Tada 《Estuaries and Coasts》2010,33(2):417-427
Long-term monitoring of water quality and phytoplankton was conducted at 19 sampling stations in Harima-Nada, eastern Seto Inland Sea, Japan for 35 years from 1973 to 2007. There were two significant long-term changes, an increase in winter water temperatures of 0.042°C year?1, and a decrease in dissolved inorganic nitrogen (DIN) from about 10 μM in the 1970s to ~5 μM in the late 1990s due to the reduction in nutrient inputs. DIN concentrations and total phytoplankton cell density were both higher during the 1970s to the early 1980s and then exhibited a significant decrease in the mid 1980s and remained relatively constant thereafter. Diatoms were the dominant phytoplankton group (>90%) over the 35-year period, and there was a dramatic shift from Skeletonema dominance (~70%) to Chaetoceros in the mid 1980s. This shift in diatom species may be attributed to differences in the life cycle of Skeletonema and Chaetoceros and the response to the decrease in DIN concentration. 相似文献
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Grazing impact of the copepod community in the Oyashio region of the western subarctic Pacific Ocean
Kazutaka Takahashi Akira Kuwata Hiroaki Saito Keiichiro Ide 《Progress in Oceanography》2008,78(3):222-240
The role of copepod grazing on the ecosystem dynamics in the Oyashio region, western subarctic Pacific was investigated during six cruises from June 2001 to June 2002. In situ grazing rates of the copepod community (CGR) were measured by the gut fluorescence method in respect to developmental stages of dominant species. In terms of biomass, more than 80% of the copepod community was dominated by six large calanoid species (Neocalanus cristatus, Neocalanus flemingeri, Neocalanus plumchrus, Eucalanus bungii, Metridia pacifica and Metridia okhotensis) throughout the year. Resulting from the observed pattern of the interzonal migrating copepods, the CGR in the Oyashio region was divided into three phases, i.e. spring (bloom), summer (post-bloom) and autumn-winter phase. During the spring bloom, late copepodites of the interzonal migrating species, N. cristatus, N. flemingeri and E. bungii appeared in the surface layer (0-50 m) to consume the production of the bloom, resulting in a high grazing rate of the copepod community (7.9 mg Chl m−2 d−1), though its impact on phytoplankton community was low due to the high primary productivity. During the post-bloom period, although the copepod community which was dominated by N. cristatus, N. plumchrus, M. pacifica and newly recruited E. bungii still maintained a high biomass, the CGR was generally lower (1.8-2.6 mg Chl m−2 d−1 for June and August 2001), probably due to the lower availability of phytoplankton. Nevertheless, the highest CGR was also observed during this period (10.5 mg Chl m−2 d−1 in June 2002). The high CGR on autotrophic carbon accounted for 69% of the primary production, suggesting that the copepod community in the Oyashio region potentially terminates the phytoplankton bloom. Abundant occurrence of young E. bungii, which is a characteristic phenomenon in the Oyashio region, was largely responsible for the high grazing pressure in June 2002 suggesting that success of reproduction, growth, and survival in E. bungii during the spring bloom is an important factor in controlling phytoplankton abundance during the post-bloom season. During autumn and winter, CGR was the lowest in the year (0.29-0.38 mg Chl. m−2 d−1) due to the disappearance of the interzonal migrating copepods from the surface layer. Diel migrant M. pacifica was the most important grazer during this period. The annual ingestion of the copepod community is estimated as 37.7 gC m−2 on autotrophic carbon (converted using C:Chl ratio of 30) or 137.9 gC m−2 on suspended particles (using C:Chl ratio of in situ value, 58-191), accounting for 13% and 46% of annual primary production, respectively. This study confirms that copepod grazing is an important pathway in carbon flow in the Oyashio region and in particular their role in the phytoplankton dynamics is significant for the termination of the spring bloom. 相似文献