1997 Fiscal Year Final Research Report Summary
Salt leaching of marine clay and its effect to the sensitivity with ground water pumping
| Project/Area Number |
08455223
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geotechnical engineering
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| Research Institution | Saga University |
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Principal Investigator |
MIURA Norihiko Saga University, Dept.of Civil Engineering, Professor, 理工学部, 教授 (00035073)
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| Co-Investigator(Kenkyū-buntansha) |
ARAKI Hiroyuki Saga University, Institute of Lowland Technology, Associate Professor, 低平地防災研究センター, 助教授 (70117315)
SAKAI Akira Saga University, Dept.of Civil Engineering, Associate Professor, 理工学部, 助教授 (00162256)
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| Project Period (FY) |
1996 – 1997
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| Keywords | marine clay / salt leaching / groundwater pumping / ground subsidence / water quality analysis / sensitivity / compressibility |
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| Research Abstract |
In order to clarify the salt leaching mechanism of The Ariake Clay Formation (marine layer) in Saga plain and the unique relationship between the phenomenon and its geotechnical properties, the depositional environment of the formation was established by measuring Oxidization-Reduction-Phase(ORP) and analysis of habitat of shell remains in the clay. The result was made with the following assumptions ; (1)Groundwater flow with artificial pumping caused salt leaching of the formation ; (2)Initially, the marine clay(Ariake clay) deposited with high void ratio influenced by sea water ; (3)High sensitivity and high compressibility of local Ariake clay had been resulted from artificial pumping for dozens of years.
Based on the above assumptions, 4 subjects have been established and investigated in this study. The report consists of ; 1. Study on depositional environment of The Ariake Clay Formation and its sensitivity ; 2. Investigation of groundwater level including the Pleistocene deposits
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; 3. Research on groundwater circulation using natural tracer method ; 4. Consideration of compression properties of marine clay based on the pore size distribution measurement. Through these subjects, various information could be obtained.
The Ariake Clay Formation can be classified into normal layer and leached one. Likewise, The Hasuike Formation(non-marine layer) can be classified from the viewpoint of salt concentration in the clay. Based on this classification, geotechnical properties of the formation could be clearly understood. Pore pressure distribution in the formation has not changed at the surface, but changed at deeper depth affected by the change in groundwater level with season. It can be considered that the distribution of salt concentration in the formation is not only affected by artificial pumping, but also by the complicated river behavior in Saga lowland area. Cementation effect is one of the important factors that should be considered in the understanding of its high sensitivity, high compressibility. Less
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