巻号一覧
35 巻, 2 号
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山口 嘉一, 田原 則雄, 松本 徳久1994 年 35 巻 2 号 p. 47-59
発行日: 1994/06/10
公開日: 2010/06/04
ジャーナル フリーRecently, 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.抄録全体を表示PDF形式でダウンロード (2917K) -
北川 隆司, 西戸 祐嗣1994 年 35 巻 2 号 p. 60-68
発行日: 1994/06/10
公開日: 2010/06/04
ジャーナル フリー広島県や島根県に分布している花崗岩や流紋岩中には, 割れ目をうめて, いわゆる粘土細脈が多く認められる。この粘土細脈中の主な粘土鉱物は雲母粘土鉱物, スメクタイト, カオリン鉱物である。雲母粘土鉱物のK-Ar年代測定を行ったところ, その形成年代は母岩の花崗岩や周辺の花崗岩のK-Ar年代とほとんど同じか, あるいはやや若い値を示す。このことは粘土鉱物をうめている割れ目 (粘土細脈) は花崗岩が固結後間もない時期に形成されたことを示している。そこで, 広島県と島根県に分布している花崗岩地域と, 周辺に花崗岩が存在している一部流紋岩地域を13の領域に分け, 粘土細脈の配行 (走向, 傾斜) を調べた。またその領域からそれぞれ代表的脈を20選び, そのK-Ar年代測定を行なった。その結果, 粘土細脈のK-Ar年代は31-80Maである。また, 粘土鉱物をうめている割れ目 (粘土細脈) の配行の解析から, それらは広域圧縮応力場で形成され, 最大圧縮応力の方向は白亜紀から古第三紀にかけて少なくとも数回変化したと推定された、すなわち, 約5000万年の間にWNW-ESE, NE-SW, E-W, NW-SEあるいはNNE-SSW, E-Wそして最後にN-SあるいはNW-SEである。今回の結果と従来貫入岩から求められている応力場の変遷とを比較すると類似点が多い。すなわち, 今まで割れ目や貫入岩の配行解析から求めていた応力場解析に対して, 具体的年代を特定することができることを意味している。このことから少なくとも広島県や島根県の花崗岩分布地域においては, 粘土細脈の配行解析は古応力場の変遷を知る上で一つの有効な方法であることを示している。抄録全体を表示PDF形式でダウンロード (1365K) -
堤 和大, 渡辺 邦夫, 菅 伊三男, 山脇 真二1994 年 35 巻 2 号 p. 69-76
発行日: 1994/06/10
公開日: 2010/06/04
ジャーナル フリーHydraulic 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.抄録全体を表示PDF形式でダウンロード (1535K) -
鈴木 清史, 高橋 学1994 年 35 巻 2 号 p. 77-78
発行日: 1994/06/10
公開日: 2010/06/04
ジャーナル フリーPDF形式でダウンロード (3256K)
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