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Volume 35 (1994 - 199･･･
- Issue 6 Pages 235-
- Issue 5 Pages 179-
- Issue 4 Pages 131-
- Issue 3 Pages 84-
- Issue 2 Pages 47-
- Issue 1 Pages 1-
Volume 35, Issue 2
Displaying 1-4 of 4 articles from this issue
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Yoshikazu YAMAGUCHI, Norio TAHARA, Norihisa MATSUMOTO1994 Volume 35 Issue 2 Pages 47-59
Published: June 10, 1994
Released on J-STAGE: June 04, 2010
JOURNAL FREE ACCESSRecently, in Japan, not a few dam sites are composed of soft rocks, such as sedimentary rocks of the Neogene, volcanic fall deposits of the Quaternary, weathered granites, and sand and gravel deposits. Soft rocks, and sand and gravel deposits are weak in strength compared to hard rocks. In addition, large seepage force will act on dam foundation during the filling of the reservoir. When dam foundation comprises of soft rocks or sand and gravel deposits, it is required to investigate whether seepage failure, such as piping, internal erosion and hydraulic fracturing, will occur, by laboratory or field test in the designing stage of dam.
In this paper, we have first introduced the standard method of laboratory seepage failure test (SFT) using disturbed or undisturbed specimens collected from dam sites.
Secondly we have examined the relationship between critical hydraulic gradient (icr) obtained from laboratory SFT and results of laboratory soil tests, such as void ratio (e), coefficient of permeability (k) and unconfined compressive strength (qu). This study has led to discovery of good correlation between icr and qu.
Thirdly we have investigated the anisotropy of icr and the difference in icr between disturbed and undisturbed specimens. This investigation has clarified the followings. According to the anisotropy of permeability, icr has the anisotropy. Although cement effect of undisturbed specimens has been recognized, they could have weak part in strength like fine fissure.
Forthly the relationship between icr and value of resistance to scour obtained from scour test has been considered in details in order to grasp seepage failure potential of dam foundation with simpler method. Since good correlation has been obtained, seepage failure potential may easily be estimated by scour test.
Finally we have proposed investigation procedure of seepage failure potential of dam foundation in consideration of the above-mentioned results.View full abstractDownload PDF (2917K) -
Ryuji KITAGAWA, Hirotsugu NISHIDO1994 Volume 35 Issue 2 Pages 60-68
Published: June 10, 1994
Released on J-STAGE: June 04, 2010
JOURNAL FREE ACCESSFractures filled with clay minerals (clay veins) occur extensively in granitic andrhyolitic rocks throughout Hiroshima and Shimane Prefectures, southwest Japan. The main constituent clay minerals are mica clay mineral, smectite and kaolin mineral. Based on K-Ar dating of mica clay mineral, the formation age of the clay veins is almost the same or slightly predates the emplacement age of the host or surrounding granitic rocks. Therefore, it is suggested that most of the clay veins were formed immediately after solidification of the host or surrounding granitic rocks.
The orientations of the clay veins in 13 specific regions in Hiroshima and Shimane Prefectures were systematically analyzed, and 20 K-Ar ages of constituent clay minerals (mainly mica clay mineral) within the veins of each region were determined, i.e. 31-080 Ma.
The orientation analysis of fractures suggests that most of the fractures were formed under a regional stress field. The azimuth of maximum principal stress axis appears to have varied at least several times during period from the Cretaceous to Palaeogene in Hiroshima and Shimane Prefectures. The maximum compression stress directions vary from WNW-ESE to NE-SW, E-W, NW-SE or NNE-SSW, E-W and finally N-S or NWSE, over a ca. 50 million year period. Comparing these results with those obtained prebiously from dyke orientations, the azimuthes of maximum compression stress axis are breafly resemble.
Thus, orientation analysis of clay veins is a useful technique to determine paleostress fields in granitic terrain.View full abstractDownload PDF (1365K) -
Kazuhiro TSUTSUMI, Kunio WATANABE, Isao SUGA, Shinji YAMAWAKI1994 Volume 35 Issue 2 Pages 69-76
Published: June 10, 1994
Released on J-STAGE: June 04, 2010
JOURNAL FREE ACCESSHydraulic properties of unsaturated rock, that are the relations among saturation, capillary suction head and relative permeability, must be properly evaluated for calculating the saturated-unsaturated groundwater flow in rock mass. However, the practical technique for evaluating the properties has been lacked because the measurements of capillary suction and small rate of flow seeping through the unsaturated rock are much difficult. The present authors newly propose a back analytical technique for evaluating the hydraulic properties.
A columnar rock specimen is prepared. The side of this specimen is completely sealed to avoid the evaporation from this side. The constant hydraulic head condition is given on the bottom of the specimen. When the air over the upper surface of the specimen is dry, water flows upwardly from the bottom through the specimen and evaporates at the upper surface. The evaporation rate is measured using evaporation sensor. The evaporation rate is the boundary flux condition of the flow through the specimen. After when the evaporation rate reaches the constant value, the specimen is broken and the vertical saturation distribution is measured. The saturation distribution can be calculated by solving the basic equation of one dimensional flow when the hydraulic properties of the specimen were given, because the boundary conditions are known. The hydraulic properties are back analytically looked for with many trial calculations. The van-Genuchten model is adapted for representing the properties and Maquet technique is used in this back analytical calculations.
The hydraulic properties of two granitic rock and three Tertiary mud stone specimen were successfully measured. Transient moisture change in the mud stone, that was observed below an actual cutface, was also well analysed using the hydraulic properties evaluated by this technique.View full abstractDownload PDF (1535K) -
Kiyofumi SUZUKI, Manabu TAKAHASHI1994 Volume 35 Issue 2 Pages 77-78
Published: June 10, 1994
Released on J-STAGE: June 04, 2010
JOURNAL FREE ACCESSDownload PDF (3256K)
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