基于应变空间多机构CG模型的地震液化大变形数值分析     

周葛  刘汉龙  井合进  陈育民  飞田哲男 《岩土力学》2016,37(8):2417-2425

砂土液化导致的地基侧向大变形是地震中许多重要的工程设施和建筑物破坏的主要原因之一。简要介绍了可进行液化大变形分析的散粒体材料本构模型--应变空间多机构CG模型,基于FLIP ROSE程序平台,建立了预测和研究倾斜地基砂土液化导致侧向大变形的二维有限元数值分析方法。采用该模型对相同工况的土工动态离心模型试验进行了模拟,通过对比超孔隙水压力、剪切波水平加速度以及地基侧向位移发现,数值预测与试验结果吻合良好,从而验证了该有限元数值分析模型的可靠性。最后利用该数值分析模型预测了倾斜率不同的地基受到相同剪切波作用时,倾斜地基不同深度产生的侧向位移。预测结果显示,随着地基深度的减小,倾斜率对于地震液化导致倾斜地基侧向大变形的影响越来越显著。  相似文献   

Regional-Scale Excess Ar wave in a Barrovian type metamorphic belt, eastern Tibetan Plateau     

Tetsumaru  Itaya  Hironobu  Hyodo  Tatsuki  Tsujimori  Simon  Wallis  Mutsuki  Aoya  Tetsuo  Kawakami  Chitaro  Gouzu 《Island Arc》2009,18(2):293-305

Laser step heating ⁴⁰Ar/³⁹Ar analysis of biotite and muscovite single crystals from a Barrovian type metamorphic belt in the eastern Tibetan plateau yielded consistent cooling ages of ca. 40 Ma in the sillimanite zone with peak metamorphic temperatures higher than 600°C and discordant ages from 46 to 197 Ma in the zones with lower peak temperatures. Chemical Th‐U‐Total Pb Isochron Method (CHIME) monazite (65 Ma) and sensitive high mass‐resolution ion microprobe (SHRIMP) apatite (67 Ma) dating give the age of peak metamorphism in the sillimanite zone. Moderate amounts of excess Ar shown by biotite grains with ages of 46 to 94 Ma at metamorphic grades up to the high‐grade part of the kyanite zone probably represent incomplete degassing during metamorphism. In contrast, the high‐grade part of the kyanite zone yields biotite ages of 130 to 197 Ma. The spatial distribution of these older ages in the kyanite zone along the sillimanite zone boundary suggests they reflect trapped excess argon that migrated from higher‐grade regions. The most likely source is muscovite that decomposed to form sillimanite. The zone with extreme amounts of excess argon preserves trapped remnants of an ‘excess argon wave’. We suggest this corresponds to the area where biotite cooled below its closure temperature in the presence of an elevated Ar wave. Extreme excess Ar is not recognized in muscovite suggesting that the entrapment of the argon wave by biotite took place when the rocks had cooled down to temperatures lower than the closure temperature of muscovite. The breakdown of phengite during ultrahigh‐pressure (UHP) metamorphism may be a key factor in accounting for the very old apparent ages seen in many UHP metamorphic regions. This is the first documentation of a regional Ar‐wave spatially associated with regional metamorphism. This study also implies that resetting of the Ar isotopic systems in micas can require temperatures up to 600°C; much higher than generally thought.  相似文献   

Seasonal Variation in Lower Trophic Level Ecosystem of Hakata Bay, Japan     

Tetsuo Yanagi  Goh Onitsuka 《Journal of Oceanography》2000,56(3):233-243

The seasonal variation in lower trophic level ecosystem of Hakata Bay, Japan is investigated using observed data from April 1993 to March 1994 and a numerical ecosystem model. Primary production was largest in September 1993 due to high DIP concentration but secondary production was largest in August 1993 due to high water temperature. Yearly averaged primary production in Hakata Bay is larger than that in the Seto Inland Sea but yearly averaged secondary production in Hakata Bay is smaller than that in the Seto Inland Sea. New production was nearly the same as regenerated production in summer but the former was larger than the latter in winter. Yearly averaged ratio of new production to regenerated production in Hakata Bay is larger than that in the open ocean.  相似文献   

On Structure and Temporal Variation of the Bifurcation Current off the Kii Peninsula   总被引：1，自引：0，他引：1  

Makoto Uchida  Junichi Takeuchi  Yoshitaka Morikawa  Youichi Maekawa  Osamu Momose  Takashi Koike  Yutaka Nagata 《Journal of Oceanography》2000,56(1):17-30

The Kii Bifurcation Current is often found along the southwest coast of the Kii Peninsula, and its frequency of occurrence reaches about 70% in the period from 1988 to 1996 (Takeuchi et al., 1998a). In order to clarify the structure and short-period variability of the Kii Bifurcation Current, detailed observations were made four times on board the R/V Seisui-maru of Mie University on October 29–31, 1996, on June 24–26, 1997, October 14–16, 1997, and December 3–4, 1997. The measured horizontal structure of the Kii Bifurcation Current indicates that the eastern portion of the Current (eastward flow near Cape Shionomisaki) consists of a part of the current zone of the Kuroshio. It is shown that the current structure, including the Kii Bifurcation Current in the vicinity of Cape Shionomisaki, is stable when the Kuroshio is flowing in a stationary straight path, but that the current structure is considerably changed when small-scale eddies pass by the cape. Such short-period variation can be monitored by using the daily variation of the sea level difference between Kushimoto and Uragami. In particular, in the case of October 29–31, 1996, when an eminent small-scale eddy passed by Cape Shionomisaki, and when the Kuroshio axis tentatively moved southwards about 50 km apart from the coast, the Kii Bifurcation Current seems to have disappeared.  相似文献   

Microplastics in the Southern Ocean   总被引：4，自引：0，他引：4  

Atsuhiko Isobe  Kaori Uchiyama-Matsumoto  Keiichi Uchida  Tadashi Tokai 《Marine pollution bulletin》2017,114(1):623-626

A field survey to collect microplastics with sizes < 5 mm was conducted in the Southern Ocean in 2016. We performed five net-tows and collected 44 pieces of plastic. Total particle counts of the entire water column, which is free of vertical mixing, were computed using the surface concentration (particle count per unit seawater volume) of microplastics, wind speed, and significant wave height during the observation period. Total particle counts at two stations near Antarctica were estimated to be in the order of 100,000 pieces km^? 2.  相似文献   

Complex vertical migration of larvae of the ghost shrimp, Nihonotrypaea harmandi, in inner shelf waters of western Kyushu,Japan     

Akio Tamaki  Sumit Mandal  Yoshihiro Agata  Ikumi Aoki  Toshikazu Suzuki  Hisao Kanehara  Takashi Aoshima  Yasushi Fukuda  Hideshi Tsukamoto  Tetsuo Yanagi 《Estuarine, Coastal and Shelf Science》2010

The position of meroplanktonic larvae in the water column with depth-dependent current velocities determines horizontal transport trajectories. For those larvae occurring in inner shelf waters, little is known about how combined diel and tidally-synchronized vertical migration patterns shift ontogenetically. The vertical migration of larvae of Nihonotrypaea harmandi (Decapoda: Thalassinidea: Callianassidae) was investigated in mesotidal, inner shelf waters of western Kyushu, Japan in July–August 2006. The larval sampling at seven depth layers down to 60 m was conducted every 3 h for 36 h in a 68.5-m deep area 10 km off a major coastal adult habitat. Within a 61–65-m deep area 5–7.5 km off the adult habitat, water temperature, salinity, chlorophyll a concentration, and photon flux density were measured, and water currents there were characterized from harmonic analysis of current meter data collected in 2008. The water column was stratified, with pycnocline, chlorophyll a concentration maximum, and 2% of photon flux density at 2 m, recorded at around 22–24 m. The stratified residual currents were detected in their north component, directed offshore and onshore in the upper and lower mixed layers, respectively. More than 87% of larvae occurred between 20 m and 60 m, producing a net onshore transport of approximately 1.3 km d⁻¹. At the sunset flooding tide, all zoeal-stage larvae ascended, which could further promote retention (1.4-km potential onshore transport in 3 h). The actual onshore transport of larvae was detected by observing their occurrence pattern in a shallow embayment area with the adult habitat for 24 h in October 1994. However, ontogenetic differences in the vertical migration pattern in inner shelf waters were also apparent, with the maximum mean positions of zoeae deepening with increasing stages. Zoeae I and II performed a reverse diel migration, with their minimum and maximum depths being reached around noon and midnight, respectively. Zoeae IV and V descended continuously. Zoeae III had behaviors that were intermediate to those of the earlier- and later-stage zoeae. Postlarvae underwent a normal diel migration (nocturnal ascent) regardless of tides, with the deepest position (below 60 m and/or on the bottom) during the day. These findings give a new perspective towards how complex vertical migration patterns in meroplanktonic larvae enable their retention in inner shelf waters before the final entry of postlarvae into their natal populations.  相似文献   

Processes controlling cobalt distribution in two temperate estuaries,Sagami Bay and Wakasa Bay,Japan     

Hyoe Takata  Tatsuo AonoKeiko Tagami  Shigeo Uchida 《Estuarine, Coastal and Shelf Science》2010

Concentrations of cobalt (Co) in surface waters from the Sagami River to northern Sagami Bay and from the Yura River to southwestern Wakasa Bay in Japan were determined in order to investigate the factors governing the distribution of this metal during estuarine mixing. Dissolved (<0.2 μm) and particulate (>0.2 μm) Co showed non-conservative mixing behavior with low or mid-salinity maxima within those two estuarine regions, indicating benthic remobilization and/or sewage input apart from riverine input during the estuarine mixing. These results are supported by a suite of complementary measurements of other parameters, such as manganese, phosphate, and suspended particulate matter concentrations. In addition, the concentration ratio of dissolved Co to total Co (dissolved plus particulate) increased along the salinity gradient, implying the potential for desorption of this metal from suspended particulate matter on estuarine mixing.  相似文献   

High organic carbon deposition in the northern margin of the Aleutian Basin (Bering Sea) before the last deglaciation   总被引：1，自引：0，他引：1  

Boo-Keun Khim  Sunghan Kim  Masao Uchida  Takuya Itaki 《Ocean Science Journal》2010,45(4):203-211

High-resolution geochemical, isotope and elemental data from core PC23A in the northern margin of the Aleutian Basin (Bering Sea) were used to reconstruct distinct paleoceanographic features of the last deglaciation (pre-Boreal[PB], Bølling-Allerød[BA], Younger Dryas[YD]). The PB and BA intervals are characterized by increased siliceous (diatom) and calcareous (coccolithophores and foraminifers) productivity represented by high biogenic opal and CaCO₃ contents, respectively. The enhanced productivity can plausibly be attributed to an elevated sea-surface nutrient supply from increased melt-water input and enhanced Alaskan Stream injection under warm, restricted sea-ice conditions. High C_org/N ratios and low δ¹³C values of sediment organic matter during the PB and BA intervals reflect the contribution of terrestrial organic matters. The PB and BA intervals were also identified by laminated sediment layers of core PC23A, characterized by high Mo/Al and Cd/Al ratios, indicating that the bottom water condition remained anoxic. High δ¹⁵N values during the same period were attributed mainly to the increased nutrient utilization and subsequent denitrification of seawater nitrate. Part of high δ¹⁵N values may also be due to incorporation of inorganic nitrogen in the clay minerals. It is worthy of note that high total organic carbon (TOC) deposition occurred approximately 3,000 years before onset of the last deglaciation. Simultaneous high C_org/N ratios and low δ¹³C values clearly suggest that the high TOC content should be related to terrestrial organic carbon input. Low δ¹⁵N values during the high TOC interval also confirm the contribution of terrigenous organic matter. Although abundant calcareous phytoplankton production under cold, nutrient-poor conditions represented by Baex data was reported for high TOC deposition preceding the last deglaciation in an earlier study of the Okhotsk Sea, the main reason for the enhanced TOC deposition in the Bering Sea is an increased terrigenous input from the submerged continental shelves (Beringia) with a sea-level rise; this is further supported by Al enrichment of bulk sediments during the high TOC deposition.  相似文献   

Quasiperiodic small meanders of the Kuroshio off Cape Ashizuri and their inter-annual modulation caused by quasiperiodic arrivals of mesoscale eddies     

Motohiko Kashima  Shin-Ichi Ito  Kaoru Ichikawa  Shiro Imawaki  Shin-Ichiro Umatani  Hiroshi Uchida  Takashi Setou 《Journal of Oceanography》2009,65(1):73-80

A quasiperiodic variation of 100–110 days in the Kuroshio path off Cape Ashizuri, resulting from the passage of small meanders, was detected by observation with moored current meters during 1993–1995. TOPEX/POSEIDON altimeter data covering 9 years showed that the quasiperiodic variation period was not persistent and modulated twice, with a ∼110-day period from mid-1993 to late 1996, a ∼150-day period from late 1996 to mid-1999, and a ∼110-day period from mid-1999 to late 2001. The quasiperiodic variations of the Kuroshio path migration were contemporaneous with the quasiperiodic arrivals of mesoscale eddies from the east along 27–32°N over the same ∼110- and ∼150-day period quasiperiodic variations. The periodic arrivals of the eddies configure the periodic variations of the Kuroshio path and its inter-annual modulation.  相似文献   

Modeling the effects of atmospheric nitrogen input on biological production in the Japan Sea     

Goh Onitsuka  Itsushi Uno  Tetsuo Yanagi  Jong-Hwan Yoon 《Journal of Oceanography》2009,65(3):433-438

The effects of atmospheric nitrogen input on biological production in the Japan Sea have been investigated using a coupled physical-ecosystem model. Comparison between the cases with and without nitrogen deposition shows a relatively large effect on primary production in the southern Japan Sea during summer to autumn, when nitrogen deposition is high and nutrient is depleted in the surface layer. The atmospheric nitrogen deposition supports > 10% of the annual export production in the nearshore region along the Japanese coast. The importance of atmospheric input as a new nutrient will grow steadily with increasing deposition into the Japan Sea.  相似文献