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Volume 53, Issue 1
Displaying 1-4 of 4 articles from this issue
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Original Article
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Takafumi UZAWA, Hideki INAGAKI, Hideki KOSAKAArticle type: Original Article
2012 Volume 53 Issue 1 Pages 2-11
Published: April 10, 2012
Released on J-STAGE: February 28, 2014
JOURNAL FREE ACCESSIn this paper, authors describe the characteristics of typical fractures in a loosened rock mass of weathered granite, northern Yamanashi Prefecture, and indicate a landslide primary deformation process leading to loosening of the rock. The loosened rock mass is divided into 1) tension crack zone, 2) conjugate crack zone, and 3) extruding deformation zone, from the head to the toe part. The stress condition and deformation process in the loosened rock mass can be estimated from characteristics and orientations of the cracks. There is a topographic step at the top part of each loosened rock mass. The displacement ratios (100X/L：X is displacement of loosened rock mass, L is length of loosened rock mass) calculated by the topographic steps are 0.8-4.0 %.
The critical displacement ratio of juvenile landslides in the weathered granite of this area is about 5 %. Compared with the previous authors' studies, the value is close to the critical displacement ratio of landslides in the Neogene sedimentary soft rock.
Topographic development pathway leading to landslide from the loosened rock mass can be indicated by displacement ratio and slope angle. The topographic development pathway of weathered granite is different from Neogene sedimentary rock and crystalline schist's topographic development pathway.View full abstractDownload PDF (9418K) -
Kunihiro HIGUCHI, Nobuaki SHITARA, Keizo UGAIArticle type: Original Article
2012 Volume 53 Issue 1 Pages 12-20
Published: April 10, 2012
Released on J-STAGE: February 28, 2014
JOURNAL FREE ACCESSThe Maebashi mudflow deposit ground saturated with ground water consists of the weakly combined volcanic ash sand. The strength of this volcanic ash sand is small as the N-value is between 3-11, which entails the possibility of liquefaction during large earthquakes. Cyclic undrained triaxial tests have been done using undisturbed samples obtained from the sand deposit. The liquefaction characteristics of the sand were investigated. From the results of the cyclic undrained triaxial tests, the liquefaction strength ratio RL was found to be 0.43-0.69, which means that the calculated resistance ratios for the liquefaction became 1.0 or more. This result contradicts with the information from N-value stated above, the reason of which is considered in this study. Furthermore, the seismic effects on infrastructures constructed on the Maebashi mudflow deposit ground are investigated and considerable reduction of their construction costs by evaluating RL correctly is suggested.View full abstractDownload PDF (8728K) -
-A Case Study of the West Yauneyama and the Tsumo Faults, Southwestern Shimane Prefecture, SW Japan-Kotaro AIYAMA, Yuji KANAORIArticle type: Original Article
2012 Volume 53 Issue 1 Pages 21-30
Published: April 10, 2012
Released on J-STAGE: February 28, 2014
JOURNAL FREE ACCESSWe conducted topographical and geological investigations in the areas along the West Yauneyama and the Tsumo faults and their extension areas, in order to review in detail characteristics and distributions of the faults in southwestern Shimane Prefecture. By combining the results with an existing gravity anomaly map and data of seismicity in the studied area, we then discuss the connectivity and slip styles of the faults.
Based on new lineament interpretation and the field investigation, we showed that the West Yauneyama and the Tsumo faults extend 10 km to the southwest and 1 km to the east in length, respectively, compared to those indicated by previous studies. A strike-slip duplex can be recognized in the Itaigawa area, Mito town, Masuda City in which the Tsumo fault meets the northeastern part of the West Yauneyama fault. Because the area surrounded by the strike-slip duplex is lower than in elevation that surrounding the strike-slip duplex, the surrounded area is regarded as a depression. Deformation structures found in some fault outcrops show that the slip on the Tsumo fault inverted from sinistral to dextral motion. The slip sense suggests that the depression surrounded by the strike-slip duplex continues to extend to the NE-SW direction as a pull-apart, which is referred to the Itaigawa Pull-Apart in this paper, and subsequently the depression may subside.View full abstractDownload PDF (14164K) -
Manabu TAKAHASHI, Masaji KATO, Naoki TAKAHASHI, Yukiyasu FUJII, Hyuck ...Article type: Original Article
2012 Volume 53 Issue 1 Pages 31-42
Published: April 10, 2012
Released on J-STAGE: February 28, 2014
JOURNAL FREE ACCESSPermeability measurement of Kimachi sandstone was carried out to obtain the permeability and specific storage under effective confining pressure and axial differential stress conditions. The Kimachi sandstone has a not clear bedding plane and cross lamina in cm size specimen, which is mainly caused by grain orientation and pore distribution in microscopic scale. We confirmed that P wave velocity show isotropic in parallel to bedding plane and vertically anisotropic in normal to bedding plane, and that major axis of grain plane assumed as an ellipsoidal shape distribute dominantly to horizontal east-west direction from microscopic observation of the thin section. Permeability for vertical direction show larger value than those for horizontal two directions. Permeability reduction with increasing effective confining pressure and axial differential stress are almost same manner for mutually perpendicular three directions, which consist of two horizontal directions parallel to bedding plane and vertical direction normal to bedding plane. Specific storage for three directions decreased with increasing effective confining pressure, and showed dominant reduction around the maximum strength. Using the data related to the connecting path and tortuosity of the Kimachi sandstone, anisotropic phenomenon for different three perpendicular directions on permeability and specific storage under various stress conditions are discussed consistently. However, it is well known that fluid flow of composite materials are rather complex, only the simple quantification of the number of connecting path or tortuosity in a limited small range could not descide systematically anisotropic transport parameter of the whole and large specimen.View full abstractDownload PDF (12043K)
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