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91.
Seasonal transition of hydrological processes in a slow‐moving landslide in a snowy region 下载免费PDF全文
Hikaru Osawa Yuki Matsushi Sumio Matsuura Takashi Okamoto Tatsuya Shibasaki Hiroyuki Hirashima 《水文研究》2018,32(17):2695-2707
A comprehensive understanding of seasonal hydrological dynamics is required to describe the influence of pore‐water pressure on the stability of landslides in snowy regions. This study reports on the results of continuous meteorological and hydrological observations over 2 years on a landslide body comprising Neogene sedimentary rocks in northern Japan, where a thick (3–5 m) seasonal snowpack covers the land surface. Monitoring of the volumetric water content in shallow unsaturated zones (<0.8 m depth) and pore‐water pressure in saturated bedrock at depths of 2.0 and 5.2 m revealed clear seasonality in hydrological responses to rainfall and meltwater supply. During snow‐free periods, both the shallow soil moisture and deep pore‐water pressure responded rapidly to intense rainwater infiltration. In contrast, during snowmelt, the deep pore pressure fluctuated in accordance with the daily cycle of meltwater input, without notable changes in shallow moisture conditions. During occasional foehn events that cause intense snow melting in midwinter, meltwater flows preferentially through the layered snowpack, converging to produce a localized water supply at the ground surface. This episodically triggers a significant rise in pore‐water pressure. The seasonal differences in hydrological responses were characterized by a set of newly proposed indices for the magnitude and quickness of increases in the pressure head near the sliding surface. Under snow‐covered conditions, the magnitude of the pressure increase tends to be suppressed, probably owing to a reduction in infiltration caused by a seasonal decrease in the permeability of surface soils, and effective pore‐water drainage through the highly conductive colluvial layer. Deep groundwater flow within bedrock remained in a steady upwelling state, enhanced by increasing moisture in shallow soils under snow cover, reflecting the convergence of subsurface water from surrounding hillslopes. 相似文献
92.
The uneven frost heave of frost-susceptible subgrade soil causes track irregularity, which highly enhances train vibration and affects the comfort and safety of railway transportation. This paper presents a coupled thermo-hydro-mechanical (THM) analysis for the freezing behavior of railway located above a box culvert. The vertical acceleration of the vehicle, an indicator of riding comfort, is predicted through a vehicle dynamic model. The results reveal that the existence of a box culvert changes the subgrade thermal pattern, leading to a deeper frost penetration depth. The frost heave amount above the box culvert is larger than the adjacent section, resulting in uneven track structure upheave and track irregularity. This frost-induced track irregularity highly affects train vibration. 相似文献
93.
GeoJournal - Examining the spatial variation of surface temperature is an important criterion to create livable urban environment. To examine the cause of heat island variation in the study area... 相似文献
94.
Evaluation of Excess Pore Water Pressure Characteristics in Sand Mat Used for Recycling Dredged Soil
The design of sand mats should be reviewed on the basis of excess pore pressure behavior, which can be obtained by combining the characteristics of soft ground with the permeability of the mats. In this study, a banking model test was performed using dredged sand as the mat material to investigate the hydraulic gradient distribution of sand mats. The results were compared with numerical analysis results utilizing Terzaghi's one-dimensional consolidation equation. The results showed that the pore pressure was influenced by an increase in the amount of settlement at the central part of the sand mat as the height of the embankment increased. The measured decrease of the pressure head due to the residing water pressure in the sand mat was delayed compared to the numerical analysis results. Accordingly, sand mats should be laid to reduce the increased hydraulic gradient at the central part of the embankment. 相似文献
95.
ABSTRACTWhen dredged soil containing coarse soil is used for the construction of reclaimed ground that is in contact with the surface of seawater, there is a high possibility of the generation of nonuniformly reclaimed ground due to the segregation of fine-grained soil from coarse-grained soil. It is difficult to assume uniform properties of reclaimed ground because the properties are defined and formed by the spontaneously segregating sedimentation. Estimation of the soil’s volume change lacks accuracy if the properties of the reclaimed ground are assumed to be always uniform. Therefore, for pump-dredged reclamation, a predictive study and various experiments are required to estimate the physics and properties of the dredged soil sedimentation. Accordingly, this study demonstrates a modeling test to understand the characteristics of the sedimentary ground using the changing ratio of fraction of the sample passing through a 75-µm sieve. The effect of particle arrangement on hindered settling properties, sedimentation properties, the distribution of water content of sedimentary ground, and physical properties can be determined by the modeling test. The study also suggests the calculation method for the travel distance of the outlet and the volume of input soil based on the experimental results. 相似文献
96.
Emission scenario dependencies in climate change assessments of the hydrological cycle 总被引:1,自引:1,他引:0
Hideo Shiogama Naota Hanasaki Yuji Masutomi Tatsuya Nagashima Tomoo Ogura Kiyoshi Takahashi Yasuaki Hijioka Toshihiko Takemura Toru Nozawa Seita Emori 《Climatic change》2010,99(1-2):321-329
Anthropogenic global warming will lead to changes in the global hydrological cycle. The uncertainty in precipitation sensitivity per 1 K of global warming across coupled atmosphere-ocean general circulation models (AOGCMs) has been actively examined. On the other hand, the uncertainty in precipitation sensitivity in different emission scenarios of greenhouse gases (GHGs) and aerosols has received little attention. Here we show a robust emission-scenario dependency (ESD); smaller global precipitation sensitivities occur in higher GHG and aerosol emission scenarios. Although previous studies have applied this ESD to the multi-AOGCM mean, our surprising finding is that current AOGCMs all have the common ESD in the same direction. Different aerosol emissions lead to this ESD. The implications of the ESD of precipitation sensitivity extend far beyond climate analyses. As we show, the ESD potentially propagates into considerable biases in impact assessments of the hydrological cycle via a widely used technique, so-called pattern scaling. Since pattern scaling is essential to conducting parallel analyses across climate, impact, adaptation and mitigation scenarios in the next report from the Intergovernmental Panel on Climate Change, more attention should be paid to the ESD of precipitation sensitivity. 相似文献
97.
Minoru Oda 《Astrophysics and Space Science》1986,118(1-2):67-70
Japan's two X-ray astronomy satellites, HAKUCHO and TENMA, have been actively in operation leading to deeper understandings of the neutron star physics. Other satellite and balloon projects have been performed under international collaborators.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
98.
Y. Fukada S. Hayakawa I. Kasahara F. Makino Y. Tanaka H. Akiyama M. Matsuoka J. Nishimura M. Oda M. Nakagawa H. Sakurai V. S. Iyenger P. K. Kunte R. K. Manchanda B. V. Sreekantan 《Astrophysics and Space Science》1976,42(1):245-248
The size of the hard X-ray source in the Crab Nebula was observed with scintillation counters on board two balloons at a lunar occulatation on 24 January, 1975. The Gaussian width of the source is 34 (+17, –14) and the center thereof is offset from the pulsar by 6±4 at position angle 102°. The observed time profile can also be fitted to an alternative model of two line sources whose intensities are 48% at 11 and 25.5% at 7 on both sides of the pulsar.Paper presented at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975. 相似文献
99.
Isao Motoyama Nobuaki Niitsuma Toshiaki Maruyama Hiroki Hayashi Shin-ichi Kamikuri Masamichi Shiono Toshiya Kanamatsu Kaori Aoki Chikako Morishita Kyoko Hagino Hiroshi Nishi Motoyoshi Oda 《Island Arc》2004,13(1):289-305
Abstract Shipboard and shore‐based investigation on siliceous and calcareous microfossil biostratigraphy, magneto‐stratigraphy and tephrostratigraphy identified numerous datum events from the sedimentary sequences of Sites 1150 and 1151 drilled on the forearc basin of northern Japan by the Ocean Drilling Program Leg 186. Some 83 datum events were selected to construct new age–depth models for the sites. Based on the reliable magneto‐stratigraphy from the Pleistocene to the Upper Miocene, which were correlated to the standard geomagnetic polarity timescale, and on excellent records of diatom and radiolarian biostratigraphy throughout the sequences, the shipboard age model was revised. Major revisions referred to stratigraphic position of the Miocene–Pliocene boundary that has been shifted more than 200 m downward in each sequence. The age–depth relations of the forearc sites represent drastic changes in the sedimentation rate—extremely high (40 cm/k.y. on average) in the Early Pliocene and low (less than 2 cm/k.y. on average) in the Middle Miocene—and several hiatuses exist throughout the sequence. The drastic changes can be related mostly to changes in diatom sedimentation and the tectonics of the Japanese Island Arc. Local ages for some foraminiferal, calcareous nannofossil and radiolarian bioevents are estimated from the age–depth models at each site. These newly calibrated bioevents and biozones as well as established diatom biostratigraphy are incorporated into the updated magneto‐biochronologic timescale, which will contribute to an improvement in biochronologic accuracy of Neogene sediments in northern Japan and adjacent areas. 相似文献
100.
Mean sea level variations in the eastern Asia region during 1950 to 1991 are investigated with the use of observed sea level data at 16 stations. It is suggested from the data analysis, that the main cause of long-term sea level variation in this region may be the plate tectonic processes. The mean sea levels along the eastern coasts of Japan and the Philippines, and that along the southern coast of Indonesia have risen due to the subsidence of Pacific, Philippine and Australian plates under the Eurasian plate, respectively. On the other hand, the mean sea levels along the western coasts of Japan and the Philippines, and that along the northern coast of Indonesia have fallen. The distribution map of mean sea level rise at the year 2030 from 1985 in this region is presented on the basis of the results of this work and IPCC (1990). 相似文献