All issues
Volume 43 (2002 - 200･･･
- Issue 6 Pages 345-
- Issue 5 Pages 270-
- Issue 4 Pages 208-
- Issue 3 Pages 124-
- Issue 2 Pages 66-
- Issue 1 Pages 2-
Volume 43, Issue 5
Displaying 1-7 of 7 articles from this issue
- |<
- <
- 1
- >
- >|
-
Evaluation using Geophysical Exploration and Observed Field DataKoichi SUZUKI, Eiki ITO, Masahiro CHIGIRA2002 Volume 43 Issue 5 Pages 270-283
Published: December 10, 2002
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSWe monitored behavior of rainwater infiltration using an electrical survey and a TDR method at slopes site consist of weathered coarse-grained granite that had been excavated 12 years before. We also visualized the loosened zone depended on weathering using an electrical survey, a seismic reflection method, and a penetration test. In addition, we investigated the loosening process by measuring physical properties and observing rock textures of weathered granite samples. The results are as follows: 1) Infiltration of rainwater into the ground was successfully visualized using electrical method, which indicated that a surface part of weakly weathered granite, to a depth of 1m from the slope surface, has experienced wetting and drying cycles according to heavy rain and dry periods. The TDR data showed that water content by volume increased from some 10% at dry periods to some 20% by heavy rainfall. Water content decreased rapidly after the end of rainfall. 2) Weakly weathered granite in the lower parts decreased bulk density about 0.4gf/cm3, N10-values to 3-15, and increases porosity by some 10%. These changes have reached to a depth of 40cm from the slope surface. In contrast, strongly weathered granite did not change noticeably its bulk density, N10-values, and porosity after the excavation. 3) Saturation, porosity, and water content profiles which were analyzed using resistivity and P wave velocity data matched to the results by the TDR method and the penetration test. 4) Above mentioned, it is inferred that weathered granite in the study site increased the number of micro-cracks and widened their apertures in the surface part of slopes in response to stress release and the repetition of wetting and drying, and resultantly it became deteriorated during 12 years. These changes occur remarkably in weakly weathered granite than in heavily weathered zone.View full abstractDownload PDF (5861K) -
Hiroshi SUENAGA, Kenzo KIHO, Tetsuji OKADA2002 Volume 43 Issue 5 Pages 284-292
Published: December 10, 2002
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSPermeability of sedimentary rock obtained as a core sample from the deep underground was measured in the laboratory. To evaluate permeability anisotropy, i. e. the difference between horizontal and vertical permeability in the bedding plane, permeability of samples shaped from the core in the parallel or orthogonal direction were determined. Consequently, it was indicated that the permeability in the direction parallel to the bedding plane was larger than that in the direction perpendicular to it. An influence on the permeability anisotropy evaluation with different method of horizontal and vertical sample acquisition was examined. As a result, it was considered that permeability anisotropy measured by using the same sample was evaluated more appropriately than that measured by using two samples obtained from neighborhood for fine sandstone and mudstone. A relationship between porosity or seismic velocity and permeability or permeability anisotropy was also examined to be revealed that permeability and shear wave velocity were rather related, and that permeability anisotropy had little correlation with porosity or seismic velocity.View full abstractDownload PDF (2109K) -
Numerical Case Studies under Static Boundary ConditionsHiroyuki TOSAKA2002 Volume 43 Issue 5 Pages 293-305
Published: December 10, 2002
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSFor giving basic understandings of the long-term safety of geologic isolation of high level radioactive wastes in a coastal deep subsurface region, behavior of the Freshwater-Saltwater Transition Zone (FSTZ), which might be a key factor in estimating and predicting the coastal groundwater flow field, is examined through numerical case studies. The author presents, in the sequential two papers, the results of 2-D cross-sectional model studies under static/dynamic boundary conditions.
In this paper, the numerical results under static boundary conditions are presented. They can be summarized as follows.
(a) Under the same boundary conditions, two different processes, i. e., a washing-out process starting from saltwater saturated condition and a saltwater intrusion process starting from saltwater/freshwater separated condition, produce almost the same shape of FSTZ at steady state.
(b) The lower the regional permeability becomes, the longer the time required for attaining equilibrium of FSTZ becomes.
(c) Push-out of FSTZ to sea side by freshwater may occur when the rate of infiltration is high, and/or rock anisotropy is high, and/or the topographic high exists.
(d) Existence of a fault with relatively lower permeability than the peripheral rock may have greater effect on the position and shape of FSTZ, than that with higher permeability.View full abstractDownload PDF (6673K) -
Numerical Case Studies under Dynamic Natural/Artificial Boundary ConditionsHiroyuki TOSAKA2002 Volume 43 Issue 5 Pages 306-315
Published: December 10, 2002
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSFor giving basic understandings of the long-term safety of geologic isolation of high level radioactive wastes in a coastal deep subsurface region, behavior of the Freshwater-Saltwater Transition Zone (FSTZ), which might be a key factor in estimating and predicting the coastal groundwater flow field, is examined through numerical case studies.
Following the paper No. 1, the author here presents results of case studies of 2-D cross-sectional models under dynamic natural/artificial boundary conditions. The results can be summarized as follows.
(a) Multiple cycles of the sea level change through geologic time should cause the shape of FSTZ under coastal area to deviate from the GHYBEN-HERZBERG theoretical static shape. It is caused by the difference of the velocities of sea level transgression and regression, under the insufficiency of time for equilibrium. This suggests us that static modeling without sea level change might become inadequate for practical site analysis.
(b) The shaft and tunnels might have impacts on lowering the groundwater level and pulling the FSTZ toward the repository during the operation phase of several tens of years. Time for recovery of the FSTZ back to natural position needs much longer time, while groundwater level recovers in the order of period of the operation phase.View full abstractDownload PDF (7702K) -
Takao CHAISHI, Teruyuki KIKUCHI, Shuichi MAEDA2002 Volume 43 Issue 5 Pages 316-319
Published: December 10, 2002
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSCountermeasures to decrease sediment accumulation in reservoirs are important to keep functions of reservoirs. Also in recent times an idea of unified management of sediments from mountains to the sea is increasingly promoted. On the other hand, more effective utilization of sediments for such as concrete aggregates has to be taken into account as natural resources have become scarcer.
Here we report accumulation of sediments in the reservoir in Central Japan as an example, and discuss mechanism of sediment accumulation based on many drilling and grain size distribution data.
Much sediment accumulations among mountainous areas often result in problems in functions as reservoirs and in environmental deteriorations. Formation of sediment, grain-size distributions, and sediment accumulation rates are all closely related to water level manipulation and amount of flow at flood times.
In the future, for SAKUMA dam reservoir, more serious thought of unified sediments and erosion control from mountains to the sea should carefully be examined including removal of more sediments from the reservoir, efficient use of finer materials, and returning sediments to the rivers.View full abstractDownload PDF (739K) -
[in Japanese]2002 Volume 43 Issue 5 Pages 320-327
Published: December 10, 2002
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSDownload PDF (6150K) -
Kiyoshi HISANAGA, Yuji KANAORI2002 Volume 43 Issue 5 Pages 328-332
Published: December 10, 2002
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSDownload PDF (1207K)
- |<
- <
- 1
- >
- >|