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Volume 53 (2012 - 201･･･
- Issue 6 Pages 271-
- Issue 5 Pages 218-
- Issue 4 Pages 172-
- Issue 3 Pages 112-
- Issue 2 Pages 64-
- Issue 1 Pages 2-
Volume 53, Issue 5
Displaying 1-4 of 4 articles from this issue
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Original Article
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Yusaku ISOBE, Hironori KAWAHARA, Kenji MATSUMOTO, Hiroyuki OHNO, Hiroy ...Article type: Original Article
2012 Volume 53 Issue 5 Pages 218-226
Published: December 10, 2012
Released on J-STAGE: February 28, 2014
JOURNAL FREE ACCESSOn offshore disposal site, alluvial clay layer is frequently used as the bottom hydraulic barrier. The layer thickness of hydraulic barrier should be larger than a regulated value, and must not be decreased by the settling and impact of sea-reclaimed wastes. Knowing the settling phenomena of reclaimed wastes is very important to grasp the influences of offshore constructions on the ambient environment. Although the numerical analysis methods for such phenomena have been developed in recent years, it is difficult to develop the appropriate analysis. Therefore the numerical analysis approach for the materials settling in water freely has been carried out. The target of this paper is the reproducibility of the numerical analysis approach using CIP (Constrained Interpolated Profile) method and the numerically-analyzed results obtained by CIP method are compared with experimental results.
As a result, it is revealed that the free-settling behavior of single particle can be expressed by the CIP method which models the fluid and solid body. Especially it is demonstrated that CIP method is suitable for the calculation of terminal velocity for the calculation of the impact force and dent to the bottom hydraulic barrier.View full abstractDownload PDF (3837K) -
Hironori KAWAHARA, Yusaku ISOBE, Kenji MATSUMOTO, Hiroyuki OHNO, Hiroy ...Article type: Original Article
2012 Volume 53 Issue 5 Pages 227-234
Published: December 10, 2012
Released on J-STAGE: February 28, 2014
JOURNAL FREE ACCESSOn offshore disposal site, alluvial clay layer is frequently used as the bottom hydraulic barrier. The layer thickness of hydraulic barrier should be larger than a regulated value, and must not be decreased by the settling and impact of sea-reclaimed wastes. Knowing the settling phenomena of reclaimed wastes is very important to grasp the influences of offshore constructions on the ambient environment. Although the numerical analysis methods for such phenomena have been developed in recent years, it is difficult to develop the appropriate analysis. Therefore the numerical analysis approach for the materials settling in water freely has been carried out. The target of this paper is the reproducibility of the numerical analysis approach using MPS (Moving Particle Semi-implicit) method and the numerically-analyzed results obtained by MPS method are compared with experimental results.
As a result, it is clear that the MPS method, a type of particle method, is able to express the settling situations of not only single particle but also multiparticle to some extent. The appropriate settling velocity cannot be calculated directly due to the limited capacity of current available computer. However, there is a feasibility to extrapolate a certain level of settling velocity from analysis results of several different interparticle distances.View full abstractDownload PDF (4513K) -
Toshiharu MISONOU, Hisafumi ASAUE, Katsuaki KOIKE, Jun SHIMADA, Tohru ...Article type: Original Article
2012 Volume 53 Issue 5 Pages 235-244
Published: December 10, 2012
Released on J-STAGE: February 28, 2014
JOURNAL FREE ACCESSClarifying geological structure in shallow depth under the seam bottom is important to detect latent fault, interpret spatial distribution of water quality, and identify paths of groundwater discharge at the sea bottom. Although sonic prospecting has been used widely for investigating the position and distribution of submarine active faults, it cannot detect the features related to groundwater. The Ariake and Yatsushiro Seas in central Kyushu, southwest Japan are representative closed seas in Japan, facing the Kumamoto and Yatsushiro Plains being rich in groundwater resources. For imaging the geological structure containing groundwater down to 50 m depth, a towing electric sounding method was applied to these seas with a cable of 250 m length and 20 electrodes made in the cable. Four and eight measuring lines in total 26 km length were set in the Ariake and Yatsushiro areas, respectively, and a three electrode method was used to obtain accurate data. By a potential correction that considers the thickness of sea water and a 1D inversion analysis of the corrected data, a weak feature of a normal fault and a clear high resistivity zone with 200 m wide that may be related to the groundwater discharge were clarified near the Uto peninsula. For the zones near the mouths of the Midori and Sira rivers, high resistivity zones were detected in the thick post-glacial marine clay (the Ariake clay) and its cause was interpreted as the existence of the large volume of submarine groundwater. From the inversion results of the Yatsushiro Sea lines, remarkable change of the resistivity was highlighted at the extension line of the Hinagu fault. Consequently, recent and repeated movements of the Hinagu fault that formed permeable paths of the groundwater discharge were clarified.View full abstractDownload PDF (9491K) -
Shuichiro YOKOTA, Kazuya TAKEHARA, Michiaki SATOU, Seiji SAKATA, Ken-i ...Article type: Original Article
2012 Volume 53 Issue 5 Pages 245-256
Published: December 10, 2012
Released on J-STAGE: February 28, 2014
JOURNAL FREE ACCESSIf convex-concave structure of rock surface grows on steep slopes, convex portions will become unstable and will finally collapse. To understand these processes and mechanisms, the authors have surveyed the shape characteristics of tafoni developing on steep rock slopes in the Oshihara Gorge, Shimane, Japan, and have studied their processes and geologic factors controlling them.
Rock slopes where tafoni developed are composed of coarse-grained pebbly arenite sandstone. Remarkable precipitation of gypsum and softening of rocks along upper inner wall of tafoni show that infiltrated water from the slope surface has brought about the enlargement of tafoni through salt weathering. Inner dip structure of strata influence on the process.
Although the diameter of mouth of tafoni ranges from a few centimeters to a several meters, the ratio of height/width tends to decrease roughly with the increase of its width. This means that a small ellipsoid vertically elongated changes to a large horizontally elongated ellipsoid. As a tafoni develops, upper convex portion enlarges and finally will become unstable. Arch action force supporting upper blocks will decrease with the horizontal elongation of the mouth. Consequently, the instability more increase, and finally rock fall will occur. These developments may influence the slope hazards by the occurrence of rock falls in such slopes with joint planes perpendicular to bedding planes, which dip steeply outer ward.View full abstractDownload PDF (8275K)
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