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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 3
Displaying 1-3 of 3 articles from this issue
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Hisanori WAKAMATSU, Kunio WATANABE, Shinji TAKEUCHI, Hiromitsu SAEGUSA2008 Volume 49 Issue 3 Pages 126-138
Published: August 10, 2008
Released on J-STAGE: November 04, 2011
JOURNAL FREE ACCESSIt is important to understand and quantitatively classify the characteristics of local groundwater flow indicated by the water level fluctuation in wells. In this study a method to evaluate the similarities of water level fluctuation between wells is proposed. Linear regression models are constructed with independent variables such as rainfall and water level of other wells. Well similarity is estimated from model parameters (regression coefficients and model fitness). Regression coefficients are calculated with Genetic Algorithm (GA); with GA identification of parameters is easier even in a complicated model.
The method was applied to twelve wells in the Tono area in central Japan. Although groundwater level fluctuation is primarily affected by rainfall and pumping conditions, different geological conditions should also cause different types of water level. Models using water level in other wells, as well as models using preceding rainfalls and atmospheric pressure, suggest that water level fluctuation data of the wells are classified into groups rAflecting the geological conditions. This is explained by the difference in the property of pressure propagation for rain infiltration among the units. Additionally, comparison of model fitness between the models can be used for estimating the extent of these factors' effectView full abstractDownload PDF (2188K) -
Yoshiki INOHARA, Takahiro OYAMA, Yuji TORIGOE2008 Volume 49 Issue 3 Pages 139-149
Published: August 10, 2008
Released on J-STAGE: November 04, 2011
JOURNAL FREE ACCESSMagnetic susceptibility measurements of the drilled cores and the tunnel wall which consists of Neogene sedimentary rocks were made at the Rokkasyo village, Simokita Peninsula, Japan. Tuff, Sandstone, Mudstone of the Neogene Takahoko formation distributing in this area are slightly deformed and displaced by the submarine sliding before consolidation. The Takahoko formation has neither key layers nor geological distinctions for the strata correlation, but it has a pattern characterized by the magnetic susceptibility. The geological structure, the geological discontinuity and the oxidation front in the Takahoko formation can be distinguished through the magnetic susceptibility measurements.View full abstractDownload PDF (5110K) -
DIOP Souleymane, Yujiro OGAWA, Ming ZHANG2008 Volume 49 Issue 3 Pages 150-163
Published: August 10, 2008
Released on J-STAGE: November 04, 2011
JOURNAL FREE ACCESSThis paper reports field observations and new experimental data designed to clarify the response of sandstones and siltstones to cyclic wetting and drying. A methodology is proposed to understand the mechanism of disintegration of rocks due to cyclic wetting and drying. These methods were chosen after critical analysis of field observations of coast typified by cliffs where frequent moisture changes to the rocks were observed to be operative. The importance of mineralogical composition and physical properties of rocks on the overall breakdown mechanism is emphasized. The experimental results showed that the water absorption capacity appears to exert highly significant control over the rate of disintegration of rocks investigated. The results also revealed that fracture induced deterioration only occur in siltstones. The proportion of the initial flaws in the rock fabric is important for determining the rate of disintegration. We suggested that the data are consistent with a model that assumes that the coupled relationship between the amount of swelling minerals and the small scale heterogeneity (flaws) of the material are major controlling factors for fracture initiation within the rock mass and the consequent repetitive breakdown. The findings obtained from this study may offer practical considerations in understanding the mechanism of rock mass breakdown, and enable design for the control of minor rockfall and cliff degradation to be made on a rational basis.View full abstractDownload PDF (4007K)
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