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431.
432.
Monitored and simulated variations in matric suction during rainfall in a residual soil slope 总被引:1,自引:0,他引:1
Aurelian C. Trandafir Roy C. Sidle Takashi Gomi Toshitaka Kamai 《Environmental Geology》2008,55(5):951-961
This research combines field, laboratory and numerical investigations to estimate the development of a wetting front within
a 1.2 m residual soil mantle on a steep forested slope during rainfall events. The field-monitored variations in matric suction
due to rain-water infiltration during various events revealed that the maximum infiltration rate was much higher when the
wetting front resided in the upper 20 cm of soil compared to the case when the wetting front advanced to depths > 20 cm. Laboratory
investigations on soil hydraulic properties (i.e., soil water characteristic curve, and hydraulic conductivity) were useful
to establish the parameters of a multilayer finite-element model for one-dimensional vertical infiltration. These parameters
were subsequently calibrated by matching the predicted and field measured transient pore water pressure responses during actual
rainstorms with irregular rainfall patterns. The calibrated simulation model was used to assess the migration of the wetting
front under uniform rainfall with different intensities. Based on the numerical results, a hyperbolic equation was developed
to predict the duration of uniform rainfall required for the propagation of wetting front to a certain depth for a given rainfall
intensity. The proposed equation was subsequently tested against field-monitored advancements of the wetting front during
real rainstorms with variable rainfall intensity. 相似文献
433.
434.
Takashi?SasaokaEmail author Tri?Karian Akihiro?Hamanaka Hideki?Shimada Kikuo?Matsui Masatomo?Ichinose 《Geotechnical and Geological Engineering》2016,34(2):671-678
The basic objectives of mine roadways are to provide sufficient cross sections to accommodate equipment, transport, personnel travel and ventilation. However, many roadways become damaged to the extent of needing maintenance, generally dinting, and in some cases requiring re-ripping. Strata conditions play important effects on stability of roadways and other mining activities. Weak rocks cause excessive roadway closures, and water softens some rocks and worsens the closure problem. Therefore, study on effect of mine water on the stability of underground coal mine roadways is important for underground coal mine development. A scientific discussion on the effect of water on the stability of roadways is given on the basis of results obtained by means of field investigation and laboratory tests. Based on analysis, rock in saturated condition has only between 0.19 to 0.49 of its compressive strength and 0.17 to 0.59 of its tensile strength in dry condition. Among the coal measures rock in research area, water has the most obvious effect on the strength reduction of shale. The slaking behavior of shale has also been the worst among the other. Field investigation of roadway driven in shale shown vertical closure in the wet and dry condition area reached 40–60 and 5–15 cm respectively, in 30 days after the drivage. Among the measures, drainage is considered to be the most economical and simplest method to reduce the water content in the rocks or the rock masses. 相似文献
435.
Kazunori Arita Takashi Ikawa Tanio Ito Akihiko Yamamoto Matsuhiko Saito Yasunori Nishida Hideyuki Satoh Gaku Kimura Teruo Watanabe Takeshi Ikawa Toru Kuroda 《Tectonophysics》1998,290(3-4):197-210
This study is the first integrated geological and geophysical investigation of the Hidaka Collision Zone in southern Central Hokkaido, Japan, which shows complex collision tectonics with a westward vergence. The Hidaka Collision Zone consists of the Idon'nappu Belt (IB), the Poroshiri Ophiolite Belt (POB) and the Hidaka Metamorphic Belt (HMB) with the Hidaka Belt from west to east. The POB (metamorphosed ophiolites) is overthrust by the HMB (steeply eastward-dipping palaeo-arc crust) along the Hidaka Main Thrust (HMT), and in turn, thrusts over the Idon'nappu Belt (melanges) along the Hidaka Western Thrust (HWT). Seismic reflection and gravity surveys along a 20-km-long traverse across the southern Hidaka Mountains revealed hitherto unknown crustal structures of the collision zone such as listric thrusts, back thrusts, frontal thrust-and-fold structures, and duplex structures. The main findings are as follows. (1) The HMT, which dips steeply at the surface, is a listric fault dipping gently at a depth of 7 km beneath the eastern end of the HMB, and cutting across the lithological boundaries and schistosity of the Hidaka metamorphic rocks. (2) A second reflector is detected 1 km below the HMT reflector. The intervening part between these two reflectors is inferred to be the POB, which is only little exposed at the surface. This inference is supported by the high positive Bouguer anomalies along the Hidaka Mountains. (3) The shallow portion of the IB at the front of the collision zone has a number of NNE-dipping reflectors, indicative of imbricated fold-and-thrust structures. (4) Subhorizontal reflectors at a depth of 14 km are recognized intermittently at both sides of the seismic profile. These reflectors may correspond to the velocity boundary (5.9–6.6 km/s) previously obtained from seismic refraction profiling in the northern Hidaka Mountains. (5) These crustal structures as well as the back thrust found in the eastern end of the traverse represent characteristics of collisional tectonics resulting from the two collisional events since the Early Tertiary. 相似文献
436.
Shigeru Terashima Kohei Sato Masahiro Taniguchi Takashi Okai Noboru Imai 《Geostandards and Geoanalytical Research》2003,27(3):259-271
Two new geochemical reference materials, copper ore JCu-1 and zinc ore JZn-1 have been prepared by the Geological Survey of Japan (GSJ) for the determination of major and minor elements and isotopic compositions. JCu-1 is a sample of Cu-bearing sulfide ore typical of the Kamaishi mine in Iwate Prefecture, Japan, and is composed mainly of hedenbergite, chalcopyrite, quartz and calcite. Pyrrhotite, magnetite and actinolitic amphibole were also commonly found. The Zn-rich ore, JZn-1 is a crude ore from the Kamioka Pb-Zn mine in Gifu Prefecture, Japan. The sample consists of hedenbergite, quartz, calcite, sphalerite and epidote as main crystalline phase. Homogeneity test results showed that all studied constituents including ore elements such as Cu, Pb and Zn can be considered to be homogeneously distributed. Provisional collaborative analyses were carried out in ten laboratories, and the data were evaluated using a robust statistical method using z-scores. Recommended values for a number of major elements including TiO2 , Al2 O3 , MnO, MgO, CaO, Na2 O, K2 O, Fe (total), Zn, Cu and Pb were established. In addition, information values for eighteen major, minor and trace elements are presented to support future collaborative analyses. 相似文献
437.
438.
Deep convection seesaw controlled by freshwater transport through the Denmark Strait 总被引:1,自引:0,他引:1
Akira Oka Hiroyasu Hasumi Naosuke Okada Takashi T. Sakamoto Tatsuo Suzuki 《Ocean Modelling》2006,15(3-4):157
Observations of deep ocean temperature and salinity in the Labrador and Greenland Seas indicate that there is negative correlation between the activities of deep convection in these two sites. A previous study suggests that this negative correlation is controlled by the North Atlantic Oscillation (NAO). In this study, we discuss this deep convection seesaw by using a coupled atmosphere and ocean general circulation model. In this simulation, the deep convection is realistically simulated in both the Labrador and Greenland Seas and their negative correlation is also recognized. Regression of sea level pressure to wintertime mixed layer depth in the Labrador Sea reveals strong correlation between the convection and the NAO as previous studies suggest, but a significant portion of their variability is not correlated. On the other hand, the convection in the Greenland Sea is not directly related to the NAO, and its variability is in phase with changes in the freshwater budget in the GIN Seas. The deep convection seesaw found in the model is controlled by freshwater transport through the Denmark Strait. When this transport is larger, more freshwater flows to the Labrador Sea and less to the Greenland Sea. This leads to lower upper-ocean surface salinity in the Labrador Sea and higher salinity in the Greenland Sea, which produces negative correlation between these two deep convective activities. The deep convection seesaw observed in the recent decades could be interpreted as induced by the changes in the freshwater transport through the Denmark Strait, whose role has not been discussed so far. 相似文献
439.
Toshinori Takashi Tateki Fujiwara Toshiaki Sumitomo Wataru Sakamoto 《Journal of Oceanography》2006,62(1):105-113
Intrusions of the warm, oligotrophic surface slope water (SSW) and the cold, nutrient-rich bottom slope water (BSW) from the
continental slope influence the annual variations in water temperature and nutrient concentrations in the Kii Channel in August.
In order to evaluate the relationships between both these intrusions and the distance of the Kuroshio axis from Cape Shionomisaki
(Kuroshio distance), a Distance-Intrusion-Diagram (DID) for temperature, which can reproduce the vertical temperature profile
of the channel, was constructed by analyzing the temperature and Kuroshio distance records in August for 1967–2001. DIDs for
nutrients (nitrate and phosphate) are also constructed by using the relationship between the nutrient concentration and water
temperature. The only explanatory variable in the DIDs is the Kuroshio distance. The DID for temperature predicts that the
SSW occupies almost the entire water column when the Kuroshio approaches Cape Shionomisaki (Kuroshio distance = 18.5 km).
When the Kuroshio distance lies in the range 18.5–74 km, the BSW thickness increases proportionally to the Kuroshio distance
increment while the SSW thickness decreases. The BSW occupies the largest portion of the channel when the Kuroshio distance
is 74 km. Further, beyond 74 km, the BSW thickness reduces gradually. Yearly variations in the temperature and concentrations
of nitrate and phosphate were hindcast with the DIDs. The results revealed that the Kuroshio distance contributes 70%, 35%,
and 30% of the variances in temperature, nitrate concentration, and phosphate concentration, respectively. 相似文献
440.
Takashi Ichiye 《Journal of Oceanography》1970,26(6):340-353
Scaling of the equations of motion of the Antarctic Circumpolar Current indicates that the Rossby number and the Ekman number
are 10−4 to 10−5 but the vertical Ekman number may reach unity in the bottom boundary layer. The equations of motion are integrated vertically
from the surface to the bottom and averaged over a latitude circle. The resulting equation in the meridional direction is
predominantly geostrophic, whereas the main terms of the equation in the zonal direction are the wind stress and the bottom
stress. When the vertical eddy viscosity near the bottom is of the order of 102cm2/sec, the total zonal transport through the Drake Passage computed from the balance of the wind stress and the bottom stress
equals 260×106m3/sec, the amount determined byReid andNowlin (1970) from observations.
The northward transport reduces the eastward transport corresponding to the wind stress of the westerlies in the A. C. C.
through the Coriolis' term in the vertically integrated equation of motion of the zonal direction. South of the Drake Passage,
such reduction reaches about ten percent of the wind-driven transport mainly due to the peripheral water discharge. North
of the Drake Passage, the northward transport may be generated by the effect of the South American coast which prevents free
eastward movement of the A. C. C., causing a wake to the east. This transport may contribute to a part of the northward transport
of the bottom water postulated byMunk (1966). The effect of the horizontal eddy viscosity in the zonal transport equation is negligible except near the Antarctic
coast, if the eddy viscosity is less than 109cm2/sec. 相似文献