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Volume 37 (2000 - 200･･･
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Volume 37, Issue 4
Displaying 1-10 of 10 articles from this issue
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Hiroyuki MAEDA, Hiromasa HIURA2001 Volume 37 Issue 4 Pages 1-9_1
Published: March 15, 2001
Released on J-STAGE: February 25, 2011
JOURNAL FREE ACCESSThe geology of the Yasukuni landslide area consists mainly of tuffaceous clastic rocks and acidic volcaniclastic rocks of the Upper Miocene Ikutawara Formation, in which an interstratified illite/smectite minerals zone exists, formed by hydrothermal alteration related to the 8.1-7.7 Ma Ryuo hydrothermal system. The slide clays and debris contain large amounts of interstratified illite/smectite minerals. The occurrence of the Yasukuni slide is strongly related to the unstable nature of the interstratified illite/smectite minerals zone, the bulk of which is swelling clay mineral. This fact is useful in evaluating landslide risk and creating a hazard map of such slides in ancient and active hydrothermal fields.View full abstractDownload PDF (3045K) -
Satoru OHTSUKA, Yoshifumi MIYATA2001 Volume 37 Issue 4 Pages 10-17_1
Published: March 15, 2001
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSPore water pressure loading test of clay was carried out to investigate a shear resistance of clay in land-slide slope. From the observation on shear deformation of the clay, two threshold magnitudes for pore water pressure were found out where the deformation of testing specimen rapidly increased. Through a series of pore water pressure loading tests of clay, the yield points were found to locate on the critical state line de-scribed by the shear resistance angle φ'. It suggests the design based on the yield point corresponds to that of residual strength. The transmittance time of pore water pressure from the bottom to the top of soil specimen was measured to get longer after the pore water pressure was over the yield point. The deformation of soil specimen took place very slowly as the pore water pressure closing to the failure point. The reason for the slow failure was concluded that the soil deformed with the water migration and the progressive failure of soil specimen proceeded with strain softening of soil. It suggests the reason for the slow failure of landslide. The pore water pressure loading test was simulated with the constitutive equation by Hashiguchi. The yield and failure points were shown to be well estimated.View full abstractDownload PDF (4796K) -
Keizo UGAI, Fei CAI, Ying ZHENG2001 Volume 37 Issue 4 Pages 18-23_1
Published: March 15, 2001
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSAbstract Piles have been successfully applied to stabilize landslides and slopes. In the existing design methods the necessary stabilizing force supplied by the piles is determined with the prescribed safety factor using the conventional limit equilibrium method, and the bending moment and shear force in piles are evaluated using the subgrade reaction method. However, as the three-dimensional soil-pile interaction exists in the slopes stabilized with piles, much more investigations are necessary to understand the interaction mechanism and the exact evaluation of the stabilizing effect. In the present study the three-dimensional elasto-plastic finite element method with the reduced shear strength is presented and used to predict the stabilizing effects of two rows piles on the slope stability. The effects of the pile arrangements and pile head conditions to connect the two rows piles on the stabilizing effect are analyzed and investigated. The numerical results indicate that the proposed elasto-plastic FEM with the reduced shear strength has the ability to evaluate reasonably the stabilizing effects of piles on the slope stability. It is possible for the proposed method to investigate the stabilizing mechanism of piles in the slopes and to determine effectively the number, arrangement, and connection of piles.View full abstractDownload PDF (3646K) -
Keizo SASAKI, Shinya NAKAMURA, Yaming ZHOU, Seiichi GIBO2001 Volume 37 Issue 4 Pages 24-32_1
Published: March 15, 2001
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe Himekawa melange is composed of serpentine sheets overthrusted into Mesozoic-Paleozoic rock. This melange has been classified as geotectonic and is associated to a serpentine matrix. The O'dokoro landslide is found within this geological setting. The slip surface of this landslide was formed by transformation of the existing deep seated overthrust fault at a depth of about 60 to 100 m from ground surface. The slickensided slip zone surface is formed by a mixture of the original fault-clay gouge and the clay resulting from transformation along the fractured zone. Fault-clay material is dominating and showed a low residual strength in the presence of high effective normal stress, at preferred clay mineral orientation. Fractured zone-clay in turn, exhibited high residual strength. The presence of preferred-oriented clay minerals originated from nonserpentinized rocks is considered indispensable to the occurrence of large-scale landslides.View full abstractDownload PDF (5091K) -
Takahiko FURUYA2001 Volume 37 Issue 4 Pages 33-40_1
Published: March 15, 2001
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSSlope failure phenomena which was caused by the CHI-CHI earthquake was investigated, and a following knowledge was obtained. The slope failures divided into two main types. The one is concurred with a large number of small-scale landslides which are moved at high speed, and the other is the enormous rock formation landslide. The fomer is mainly constituted sand and gravel layer of the plasticity or brittle hard rocks, and arise in strong motion area of above 250gal. The latter look at the pelitic rock regions. They are difficult to occure landslides caused by the earthquake in general. However, enormous landsildes arose by the CHI-CHI earthquake. It seems that is related to Buckling based on the defomation of the rock formation which is affected by fault activity and seating phemomena.View full abstractDownload PDF (10590K) -
Takekawa-Osashi Landslide, Southern Hokkaido, JapanJun TAJIKA, Sunao OHTSU, Kazuo AMEMIYA, Shigeru WADA2001 Volume 37 Issue 4 Pages 41-48_1
Published: March 15, 2001
Released on J-STAGE: February 25, 2011
JOURNAL FREE ACCESSIn early September 1997, hillside cut for road construction caused small-scale landslide in the northeastern mountains of Matsumae peninsula, Hokkaido. The slope movement is characterized that bedded hard shale bent valleyward and back-facing steps occurred on the cut-slope. Morphology and geology of the slope indicate that gravitational bending fold had already formed in the Miocene hard shale formation before breaking out of the movement. Therefore, it seems that the landslide was gravitational fold rapidly proceeded by unloading of the lower slope. One of the geological causes of the movement is existence of fine acid tuff, includes smectite clay and been easily changed to slip surface by bending, interbedded in the hard shale. Thick and hard shale intimately developing small joints is relatively flexible to deformation.View full abstractDownload PDF (9010K) -
Tetsuro YAMAMOTO, Motoyuki SUZUKI, Yoshihiko YOSHIWARA, Toshihiko MIYA ...2001 Volume 37 Issue 4 Pages 49-57_1
Published: March 15, 2001
Released on J-STAGE: July 04, 2011
JOURNAL FREE ACCESSThe authors investigated slopes that failed during heavy rainfall, focusing especially on those in Yamaguchi prefecture, in terms of geology, petrology, and ground engineering. In our previous paper, it was shown that many of these slopes failed due to the sliding on discontinuous planes such as joint and schistosity planes. Furthermore, irrespective of the kind of rock involved, those failures have frequently occurred along thin glossy black soil layers with very smooth surfaces that have precipitated on discontinuous planes.
Thereafter we also had the opportunity to examine six slopes in Yamaguchi prefecture which were either stable or had failed, and on whose discontinuous planes existed thin glossy black soil layers with a thickness of 0.4 to 6.0mm. As the same results as those obtained by previous study, chemical, mineralogy, and physical examinations showed that the black coloring is due to amorphous manganese oxides and hydrates having fine grains. Furthermore, direct shear tests have shown that the internal friction angle between the very smooth black soil layers is 23.3°, and the cohesion is 7.6kPa. We suggest that the strength parameter should be used for stability analyses of slopes having thin glossy black soil layers on discontinuous planes.View full abstractDownload PDF (10794K) -
Shin IWANAGA2001 Volume 37 Issue 4 Pages 58-65_1
Published: March 15, 2001
Released on J-STAGE: February 25, 2011
JOURNAL FREE ACCESSThe mountainous district of Nisikubiki is underlain by Neogene marine sedimentary muddy stones, which have substantially reduced strength as a result of folding, distribution of cap rocks and severe weathering. In general the clastic formations have been altered to soft clay-rich soils.
Therefore landslides activity has been particularly intensive at locations around in this district, which is one of the most intensive areas in Japan. But occurrence of landslide is slightly less than Higasikubiki mountainous district.
In this paper author presents the relationship of landslide occurrence with geology and soil composition.View full abstractDownload PDF (7963K) -
At fractured slates in the Haruki RiverOsamu NAGAI, Toshihiko SETO, Masato JOGASAKI, Hiroyuki NAKAMURA2001 Volume 37 Issue 4 Pages 66-73_1
Published: March 15, 2001
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSIn Mar., 1998, Fujikawa Sabo Works Office, Ministry of Construction set up a remote surveillance camera at the upper reach of the Haruki River to transmit pictures of the collapsed slope to the office by satellite telecommunication for the purpose of observation through a year. The interrelations between occurrence time of rock fall due to the freeze and thaw, and air temperature have become clear by analyzing the pictures of the collapsed slope and fluctuation of air temperature at the crushed slates in the Haruki River. The pictures transmitted from the observation site show that fall of rock fragments from the collapsed slope began in the end of February triggered by a rise in air temperature. And according to the analysis of the transmitted pictures and a survey of the talus cones at the observation site, eroded depth at the collapsed slope in winter season of 1999 is 4.9cm.View full abstractDownload PDF (8637K) -
Msatake YURE, Makoto OKAMURA2001 Volume 37 Issue 4 Pages 74-81_1
Published: March 15, 2001
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe Kage Landslide in the Mikabu Greenstone Belt is a well-known laege-scale landslide, central Shikoku. Major three landslide events are recognized after 21, 300 y BP determind by C14 age analysis from boring cores. Sliding plane mainly consists of smectite-group clay minerals derived from highly weathered hyaloclastite (greenstone group) sheets.View full abstractDownload PDF (10109K)
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