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Volume 42, Issue 1
Displaying 1-7 of 7 articles from this issue
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Ken-ichi NISHIYAMA, Yosei MIZUKAMI, Katsuaki KOIKE, Yukinori MATSUKURA2001 Volume 42 Issue 1 Pages 2-14
Published: April 10, 2001
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSTemporal changes in pore structure due to weathering during 350ka were examined using sandstone gravel in fluvial terrace deposits which were distributed in the Miyazaki Plain, south Kyushu. The time between the age of each terrace formation and the present was assumed to be the weathering period.
Using rock samples taken from the outcrop in each terrace, (1) microstructure of rock samples were observed through an optical microscope and X-ray CT Scanning analysis, (2) specific gravity and effective porosity of the samples were measured, and (3) pore size distribution (PSD) of rock samples were measured by a mercury intrusion porosimetry.
Main results are summarized as follows: (1) the optical microscope observation shows that pores are connected due to weathering, (2) the CT values decrease with increasing weathering period, (3) the specific gravity decreases and the effective porosity increases with increasing weathering period, and (4) the pore radius and the pore volume increases with increasing weathering period, (5) the specific surface area increases with constant rate during 350ka. These results suggest that increasing of pores in gravel with increasing weathering period is derived from leaching of the matrix minerals with a small specific surface area.View full abstractDownload PDF (4217K) -
Masuyuki UJIHIRA, Youhei KAWAMURA, Kiyoshi HIGUCHI, Masashi SATOH, His ...2001 Volume 42 Issue 1 Pages 15-23
Published: April 10, 2001
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSIt is considered that cable sensor for vibration detection is useful, for instance, to detect the rock falling or small failures of a slope before the occurrence of a big failure. The original cable sensor is susceptible to be yielded by the tensile force, because whose tensile strength is not so enough (40 to 50 kgf). Authors have developed the steel wire cable sensor in which original cable sensor is placed instead of the string of hemp in the central portion. It was necessary to test the sensitivity of this remodeled steel wire cable sensor. As a result of the sensitivity test, following points were clarified: 1) Sensitivity of the steel wire cable sensor does not decrease when the sensor is fixed rigidly or glued continuously to the surfaces of stiff structure made of concrete or steel. 2) Sensitivity of the steel wire cable sensor decreases to 60% against the output of original cable sensor when the cable sensor is buried in the soft land. However, it was confirmed that output level was enough to use practically. In conclusion, the steel wire cable sensor could be used practically to various places to detect vibrations.View full abstractDownload PDF (2152K) -
Tetsuro HIRONO, Weiren LIN, Satoru NAKASHIMA, Manabu TAKAHASHI2001 Volume 42 Issue 1 Pages 24-29
Published: April 10, 2001
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe images of micro pores in geomaterials were visualized using an atomic force microscope. The hollow parts of AFM-image showed void space by the comparison with SEM-image. The AFM-image was transferred into the binary image of void structure by threshold at the grading scale based on the pore-size distribution and effective porosity. We can derive the geometric information, such as perimeter, pore square and hydraulic radius, of the visualized pore image using image-processing. The AFM is useful for the visualization and quantitative analysis of micro pore in geomaterials.View full abstractDownload PDF (3477K) -
Takeshi ICHIKAWA, Yukinori MATSUKURA2001 Volume 42 Issue 1 Pages 30-37
Published: April 10, 2001
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSShallow soil slips are a main geomorphic process occurring on the hillslopes made of loosely consolidated sandstone for Iwasaka formation in central Boso Hills, Japan, where two alternate processes are repeated; (1) the denudation by soil slips and (2) the recovery of soil layer by transported soil and weathering. The purpose of the present study is to research soil structure, to clarify the process of the recovery of soil layer and to estimate the return period of shallow soil slips on hillslope. Three shallow soil-slip scars with different ages of failure were selected for detailed investigations. Field investigations such as Doken-type penetration test, vane shear tests, permeable capability tests and sampling of sand in soil layer were carried out. Physical properties and 137Cs concentration of soil sand layer were also measured to make clear the formative processes and dating of soils. Test results enable us to estimate that thickness of transported soil layer reaches 100cm in 100-200 years after land-slipping. Above discussion suggests that the return period of shallow soil slips on hillslopes of the present study area is 100-200 years.View full abstractDownload PDF (1425K) -
Aiming LIN, Ken-ichi KANO, Tadashi MARUYAMA2001 Volume 42 Issue 1 Pages 38-41
Published: April 10, 2001
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe sand boils induced by the 2000 Western Tottori Earthquake (Mj7.3) widely occurred in reclaimed lands on the Yumigahama sand-bar, northwestern Tottori Prefecture, western Japan. It was observed at several locations that the sand boiling formed by liquefaction was continued for at least two days after the earthquake. This type of liquefaction is called “slow liquefaction” in this study. The gush height of boiled sands up to 90cm was directly observed at some locations. The ground of the sand boiled area has subsided 50cm in maximum. These phenomena will provide important information both for a quantitative evaluation of liquefaction potential of sand deposits and for a seismic hazard evaluation.View full abstractDownload PDF (1644K) -
Analysis of Primary Causes by the Existing Stability Evaluation MethodsTatsuo NOGUCHI, Tomoyasu SUGIYAMA2001 Volume 42 Issue 1 Pages 42-51
Published: April 10, 2001
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSA number of primary causes, mainly topographic and geological factors, are concerned with the occurrence of rock falls and rock slope collapses. Therefore, consideration of these primary causes is important to evaluate the rock slope stability. We analyzed the primary causes aiming to propose a more accurate and practical stability evaluation method of rock slopes along railways. In this paper, we report the results of analysis by the existing stability evaluation methods and show what kinds of primary causes are used and how great their weights are. As a whole, geological conditions and structures are given a great deal of weights, followed by slope height and slope gradient. And there are three different collapse types. The first is the rock collapses, for which conditions of crack, geological structures and slope height are important evaluation items. The second is the downfall type rock falls, for which stability of boulder stones, weathering, rock quality and slope gradient are important. The third is the separation type rock falls, which requires conditions of crack, weathering, rock quality and temperature to evaluate the stability of slope. In addition, spring water from slope and coverage of slope are essential for this purpose.View full abstractDownload PDF (2524K) -
Ming ZHANG, Hidenori ENDO, Manabu TAKAHASHI2001 Volume 42 Issue 1 Pages 52-59
Published: April 10, 2001
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSDownload PDF (1773K)
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