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Volume 49 (2008 - 200･･･
- Issue 6 Pages 318-
- Issue 5 Pages 256-
- Issue 4 Pages 204-
- Issue 3 Pages 126-
- Issue 2 Pages 64-
- Issue 1 Pages 2-
Volume 49, Issue 2
Displaying 1-4 of 4 articles from this issue
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Min MAUNG MAUNG, Kunio WATANABE, Tai SASAKI, Masahiko OSADA2008 Volume 49 Issue 2 Pages 64-77
Published: June 10, 2008
Released on J-STAGE: November 04, 2011
JOURNAL FREE ACCESSUnsaturated hydraulic property (relation between the water retention curve and hydraulic conductivity function) of soft rock must be properly estimated for analyzing the saturated-unsaturated groundwater flow such as the flow around a tunnel, rock surface and so forth. In this study a practical technique for estimating the unsaturated hydraulic property of soft rock was developed on the basis of the Campbell model and Genetic Algorithm (GA). The major objectives of the present study are the following two; 1) investigation whether or not the Campbell model can be applied to soft rock for approximating the unsaturated hydraulic properties and 2) application of GA technique for estimating two parameters included in the Campbell model. These parameters were estimated through the inverse analysis of the transient change of evaporation rates from a surface of disk shaped specimen of Tertiary sedimentary rock which are sampled from the Rokkasho area, Aomori prefecture. Two transient evaporation experiments under different atmospheric conditions were proposed for the estimation. The Campbell's parameters of 13 soft rock specimens (5 sandstone and 8 tuff breccia specimens) were estimated through those types of experiments. As the results it was clearly found that the transient change of evaporation rates can be well fitted by the Campbell model except for the region of low saturation and this fact implies that the Campbell model can be applied to the soft rock. And also it was found that, the GA is a promising technique for parameters estimation in the inverse solution method. It can be concluded that the techniques are practically for estimating the unsaturated hydraulic properties of soft rock.View full abstractDownload PDF (2587K) -
Atsushi SAGAWA, Kotaro AIYAMA, Yuji KANAORI, Takenobu TANAKA2008 Volume 49 Issue 2 Pages 78-93
Published: June 10, 2008
Released on J-STAGE: November 04, 2011
JOURNAL FREE ACCESSWe conducted an air-photo interpretation, an investigation of fault outcrops, a trench survey, and/or an array drilling survey for the northeastern part of the Tokusa-Jifuku fault (T-JF) and the central part of Sakota-Ikumo fault (S-IF) in central-eastern Yamaguchi Prefecture, in order to clarify their characteristics and activity. By the trench survey for the northeastern T-JF at Tokusa-naka, Ato Town, the age of the latest movement is estimated to range from 10, 800 to 3, 400 yrBP. Review of previous 14C dating data obtained from former trench survey of the southwestern T-JF suggests that the entire region of the fault being approximately 35km long moved at one time in a period between 6, 300 and 5, 200 yrBP. On the other hand, by trench surveying of the central part of S-IF at Ikumo-naka, Ato Town, located approximately 10km southwest of the epicenter of the 1997 Mj (Japan Meteorological Agency Scale) =6.6 earthquake which occurred in northern Yamaguchi Prefecture, it was judged that a movement of the fault occurred between 14, 400 and 8, 500 yrBP. These data of the latest fault movement, combined with those from previous studies, suggest that the fault movement tends to migrate southwestward from the S-IF to the northeast, through the T-JF, to the W. Kidoyama fault to the southwest, which constitutes the Lake Ohara -W. Yauneyama fault system.View full abstractDownload PDF (7535K) -
An Example of Toki Granite, Central JapanShoji NISHIMOTO, Emi UKAI, Kenji AMANO, Hidekazu YOSHIDA2008 Volume 49 Issue 2 Pages 94-104
Published: June 10, 2008
Released on J-STAGE: November 04, 2011
JOURNAL FREE ACCESSAlteration of deep granitic rock has been recently focused on in order to evaluate the long-term geological and geochemical changes for LPG storage, CO2 storage and high-level and low-level radioactive waste disposal, etc. In this paper, as an example, alteration in deep granitic rock was investigated using drilling core material of Toki granitic rock distributed in Gifu pref., central Japan. Detailed mineralogical and geochemical analyses show the alteration degree is correlated with the high-density fracture zone and sealed shear-fractures but not the depth. Geochemically, Ca, Fe and Mg are also decreased at the fracture zones. Mineralogically, sericite, chlorite, calcite and iron hydroxide are observed as secondary formed minerals. Biotite is replaced by chlorite along the cleavage. Plagioclase is altered to sericite in Ca-rich central zones of the crystals. Calcite usually forms the veins filling in shear-microfractures. These features can be explained by a series of hydrothermal alteration as follows: 1) alteration of biotite to chlorite yields K-rich water; 2) it enhances plagioclase replacement by sericite; and 3) it produces Ca-rich water leading to the precipitation of calcite in microfractures. Iron hydroxide is precipitated finally in microfractures and grain boundaries along groundwaterconducting fractures near the depth of 140-230m, probably due to the oxidized rainwater penetration. Consequently, it is inferred that different stages of the granite alteration is related to fracturing after the solidification. Such kind of rockwater interaction is assumed to be quite dominant in the deep granite alteration process with fracture-flow system.View full abstractDownload PDF (5892K) -
Wataru TANIKAWA, Masumi SAKAGUCHI2008 Volume 49 Issue 2 Pages 105-110
Published: June 10, 2008
Released on J-STAGE: November 04, 2011
JOURNAL FREE ACCESSThe transient pulse method is the useful method for measuring the low permeability in the impermeable rocks. This method and system is quite simple, though it takes very long time to evaluate the low permeability. In this study, we minimized the storage volume down to 4.05 cc so as to increase the sensitivity of pore pressure change during the tests. Permeabilities of three rocks were measured up to 100 MPa of confining pressure. Permeabilities of all rocks were decreased down to one order of magnitude from the initial values with an increase of confining pressure. The measured permeability of Inada Granite showed similar value with that in the previous reports. In the other rocks, permeabilities measured by transient pulse method indicated same values with that measured by steady state flow method at the same confining pressure. We did not find the differential pressure dependence on the permeability, though pore pressure dependence un the permeability was clearly obser ved. When our System is applied for permeability measurements, even very low permeability can be evaluated very quickly.View full abstractDownload PDF (1037K)
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